9512.net
甜梦文库
当前位置:首页 >> >>

Review of searches for Higgs bosons and beyond the standard model physics at the Tevatron

Review of Searches for Higgs Bosons and Beyond the Standard Model Physics at the Tevatron

arXiv:0805.3624v1 [hep-ex] 23 May 2008

Arnaud Duperrina
CPPM, IN2P3-CNRS, Universit? de la M?diterran?e, F-13288 Marseille, France e e e May 22, 2008 Abstract. The energy frontier is currently at the Fermilab Tevatron accelerator, which collides protons and antiprotons at a center-of-mass energy of 1.96 TeV. The luminosity delivered to the CDF and D? experiments has now surpassed the 4 fb?1 . This paper reviews the most recent direct searches for Higgs bosons and beyond-the-standard-model (BSM) physics at the Tevatron. The results reported correspond to an integrated luminosity of up to 2.5 fb?1 of Run II data collected by the two Collaborations. Searches covered include: the standard model (SM) Higgs boson (including sensitivity projections), the neutral Higgs bosons in the minimal supersymmetric extension of the standard model (MSSM), charged Higgs bosons and extended Higgs models, supersymmetric decays that conserve or violate R-parity, gauge-mediated supersymmetric breaking models, long-lived particles, leptoquarks, compositeness, extra gauge bosons, extra dimensions, and ?nally signaturebased searches. Given the excellent performance of the collider and the continued productivity of the experiments, the Tevatron physics potential looks promising for discovery with the coming larger data sets. In particular, evidence for the SM Higgs boson could be obtained if its mass is light or near 160 GeV. The observed (expected) upper limits are currently a factor of 3.7 (3.3) higher than the expected SM Higgs boson cross section at mH = 115 GeV and 1.1 (1.6) at mH = 160 GeV at 95% C.L. PACS. 1 4.80.Bn, 14.80.Cp, 14.80.Ly, 12.60.Jv, 12.60.Cn, 12.60.Fr, 13.85.Rm

Contents
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 Introduction . . . . . . . . . . . . The Tevatron accelerator . . . . The CDF and D? detectors . . . Standard model Higgs boson . . Higgs bosons in the MSSM . . . Extended Higgs models . . . . . Beyond the standard model . . . Charginos and neutralinos . . . . Squarks and gluinos . . . . . . . Gauge mediated SUSY breaking R-parity violation . . . . . . . . . Long-lived particles . . . . . . . . Leptoquarks . . . . . . . . . . . . Compositeness . . . . . . . . . . Extra gauge bosons . . . . . . . . Large extra dimensions . . . . . CDF signature-based searches . . Conclusion . . . . . . . . . . . . Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 2 2 3 13 19 20 20 22 25 25 27 27 28 29 30 32 32 34

1 Introduction
The standard model (SM) predicts experimental observables at the weak scale with high precision. Dea

spite the great success of this model, the electroweak symmetry breaking mechanism by which weak vector bosons acquire non-zero masses remains unknown. The simplest mechanism involves the introduction of a complex doublet of scalar ?elds that generate particle masses via their mutual interactions leading to the so-called SM Higgs boson with an unpredicted mass [1]. Furthermore, the SM fails to explain, for instance, cosmological phenomena like the nature of dark matter in the universe [2]. These outstanding issues are strong evidence for the presence of new physics beyond the standard model. Among the possible extensions of the standard model, supersymmetric (SUSY) models [3,4] provide mechanisms allowing for the uni?cation of the forces and a solution to the hierarchy problem. Particularly attractive are models that conserve R-parity, in which SUSY particles are produced in pairs and the lightest supersymmetric particle (LSP) is stable. In supergravity-inspired models (SUGRA) [5], the lightest neutralino χ0 arises as the natural LSP, which being ?1 neutral and weakly interacting could be responsible for the dark matter in the universe. This paper reports recent experimental results of direct searches for the Higgs boson and beyond-thestandard-model (BSM) physics based on data collected by the CDF and D? Collaborations at the Fermilab Tevatron collider. The dataset analyzed corresponds

e-mail: duperrin@cppm.in2p3.fr

Arnaud Duperrin

Review - Page 2

Fig. 1. Elevation view of the CDF detector in Run II [8].

to an integrated luminosity of up to 2.5 fb?1 . More details on the analyses can be found in Ref. [6,7].

3 The CDF and D? detectors

A full description of the CDF (Fig. 1) and D? (Fig. 2) Run II detectors in operation since 2001 is available 2 The Tevatron accelerator in Ref. [8,9]. Both experiments are multipurpose detectors and are in a steady state of running. Detectors The Tevatron is performing extremely well. For Run II, take data with an average e?ciency of 85%. An upwhich started in March 2001, a series of improvements grade of the detectors to improve their performance for were made to the accelerator to operate at a center- Run IIb was successfully concluded in 2006. The D? of-mass energy of 1.96 TeV with a bunch spacing of upgrade included the challenging insertion of an addi396 ns. Before the 2007 shutdown, monthly integrated tional layer close to the beam pipe of radiation-hard and peak luminosities of up to 167 pb?1 and 2.6 × 1032 silicon (L0) to improve the tracking performance. CDF cm?2 s?1 , respectively, have been achieved. Since the and D? completed calorimeter and track trigger upmost recent shutdown, beams with peak luminosity of grades to signi?cantly reduce the jet, missing energy, 3.2 × 1032 cm?2 s?1 have been delivered, with weekly muon and electron trigger rates at high luminosity, integrated luminosity and antiproton hourly produc- while maintaining good e?ciency for physics. In the following, the CDF and D? detector compotion rate reaching 58 pb?1 and 26 mA/hours, respectively. The consequence, in terms of the number of nents used in the analyses are brie?y described. Both interactions per crossing, is that the Tevatron is run- experiments use a cylindrical coordinate system around ning in a mode similar to that expected at the Large the proton beam axis in which θ and φ are the polar and azimuthal angles, respectively, and the pseudoraHadron Collider (LHC). The D? integrated luminosity delivered and recorded pidity η is de?ned as η = ? ln [tan (θ/2)]. The transsince the beginning of Run II is given in Table 1 (with verse momenta and energy of a particle are de?ned as pT = p sin θ and ET = E sin θ, respectively. In the folsimilar values for CDF). lowing, imbalance in transverse momentum is referred / to as missing transverse energy or ET . The trigger and data acquisition systems are designed to accommodate Table 1. Run II luminosity delivered by the Tevatron accelerator, and luminosity recorded by the D? experiment. the high rates and large data volume of Run II. It comprise three levels of increasing complexity with a Delivered Recorded rate of accepted events written to permanent storage of Run IIa 1.6 fb?1 1.3 fb?1 about 50-150 Hz. The beam luminosity is determined Run IIb 2.5 fb?1 2.2 fb?1 by using counters located in the forward pseudorapidTotal 4.1 fb?1 3.5 fb?1 ity region that measure the average number of inelastic p? collisions per bunch crossing. p

Arnaud Duperrin

Review of Searches for Higgs Bosons and BSM Physics at the Tevatron - Page 3

Fig. 2. Cross section of the central tracking system in the x ? z plane of the D? detector in Run II. Also shown are the locations of the solenoid, the preshower detectors, luminosity monitor, and the calorimeters [9].

3.1 CDF The tracking system consists of a cylindrical opencell drift chamber and silicon microstrip detectors in a 1.4 T magnetic ?eld parallel to the beam axis. The silicon detectors [10] provide tracking information for |η| < 2 and are used to detect collision and decay points. The drift chamber [11] surrounds the silicon detectors and covers the central rapidity region |η| < 1. The energies of electrons and jets are measured in calorimeters covering the region |η| < 3.6 and segmented into towers pointing toward the center of the detector. Jets are reconstructed from energy depositions in the calorimeter towers using a jet clustering cone algorithm [12] with a cone size of radius ?R = (?φ)2 + (?η)2 = 0.4. Corrections are applied to account for e?ects that can cause mismeasurements in the jet energy such as non-linear calorimeter response, multiple beam interactions, or displacement of the event vertex from the nominal z = 0 position. / Both the magnitude and direction of the ET are recomputed after the jet energies have been corrected. Outside the calorimeters, layers of steel absorb the remaining hadrons leaving only muons, which are detected by drift chambers and scintillation counters up to |η| < 1.5.

in front of 1.8 T toroids, followed by two similar layers after the toroids. Jet reconstruction is based on the Run II cone algorithm [13] with a cone size of 0.5 that uses energies deposited in calorimeter towers. Jet energies are calibrated using transverse momentum balance in photon+jet events. The missing transverse energy in an event is based on all calorimeter cells, and is corrected for the jet energy calibration and for reconstructed muons.

4 Standard model Higgs boson
The discovery of the Higgs boson is commonly considered to be the highest priority of particle physics today. This fundamental ingredient of the theory has not yet been observed and could be reachable at the Tevatron if the SM Higgs boson mass mH is light or near 160 GeV. The goal at the Tevatron is to ?nd evidence for the Higgs boson using the full dataset, expected to correspond to about 7 fb?1 by 2010. A considerable e?ort has been devoted in recent years to improve the theoretical predictions and they are
?

?? ??

3.2 D?

???


????

The central tracking system consists of a silicon mi??? ? crostrip tracker and a central ?ber tracker, both located within a 1.9 T superconducting solenoid. A liquidargon and uranium calorimeter covers pseudorapidities ?? up to |η| ≈ 4.2. The calorimeter has three sections, ×× housed in separate cryostats: the central one covers |η| < 1.1, and the two end sections extend the coverage ? to larger |η|. The calorimeter is segmented in depth, ? with four electromagnetic layers followed by up to ?ve ?? ?? hadronic layers. It is also segmented into projective towers of 0.1 × 0.1 size in η ? φ space. An outer muon Fig. 3. Standard model Higgs boson branching fractions system, covering |η| < 2, consists of a layer of tracking as a function of its mass [14]. detectors and scintillation trigger counters positioned
????? ?????? ??? ??? ? ? ??? ??? ?? ?? ????

Arnaud Duperrin

Review - Page 4

g t g t t
q1 W,Z H W,Z q2 q4 q3

q

H
SM Higgs production
10 3
gg → h qq → Wh

H
Z, W q,q , q
g q

TeV II

σ [fb]

Z,W t
H t t

10 2
qq → qqh bb → h

10
gg,qq → tth
TeV4LHC Higgs working group

qq → Zh

Fig. 4. Main diagrams for Higgs boson production at leading order: (top left) gluon fusion, (top right) Higgs associated production, (bottom left) vector boson fusion, (bottom right) associated production with heavy quark (top).

1 100 120 140 160 180 200
mh [GeV]

now known to good precision. The Higgs boson couples preferentially to the heaviest particles. As shown in Fig. 3, the decay mode H→b? is the dominant one b in the mass range mH < 135 GeV, with a branching fraction (Br) of 73% at mH = 115 GeV. For Higgs masses above ≈ 135 GeV the main decay mode is into W W pairs, where one of the vector bosons is o?-shell below the corresponding kinematic threshold. The discovery of the Higgs boson is also among the main reasons for the construction of the Large Hadron Collider (LHC) at CERN, which is expected to begin operation in summer 2008. The LHC was designed such that the discovery of the SM Higgs boson, if it exists, would be guaranteed up to O(1 TeV) [15], the highest energy consistent with general theoretical principles. Precision measurements, most notably of the top mass mt = 172.6 ± 1.4 GeV [16] at the Tevatron and of the W mass mW = 80.398 ± 0.025 GeV [17,18] at LEP and at the Tevatron, however provide strong indications that the SM Higgs boson should be much lighter than that upper bound, having a mass smaller than 160 GeV at 95% con?dence level (C.L.) [19]. Direct searches for the Higgs boson at LEP in the e+ e? → Z ? →ZH reaction provide a lower limit of 114.4 GeV [20], but also revealed several interesting candidate events with masses just above that lower bound. If the direct lower limit from LEP is taken into account to extract an upper bound from precision measurements, the SM Higgs boson mass upper limit becomes 190 GeV at 95% C.L. Such a mass range is favorable to the Tevatrons reach. 4.1 Higgs boson production The main diagrams for Higgs production are displayed at leading order in Fig. 4. The production cross section of the Higgs boson are summarized in Fig. 5 for p? p collisions at the Tevatron. They are small, of the order of 0.1 pb, not including the decay branching fractions, while typical backgrounds such as W +b? or Z+b? have b b

Fig. 5. Standard model Higgs boson production cross √ sections (fb) at the Tevatron ( s = 1.96 TeV) for the most relevant production mechanisms as a function of the Higgs boson mass [21].

cross sections three orders of magnitude larger. The q q →qqH vector boson fusion (VBF) process is known ? at next-to-leading order (NLO) in QCD and is marginal at the Tevatron with cross sections between 0.1-0.02 pb for masses 100 GeV < mH < 200 GeV [22]. The as? sociated production process ttH is also known at NLO in QCD and can be exploited only at the LHC [23]. The bottom fusion bb→H process is known at next-tonext-to-leading order (NNLO) in QCD in the ?ve-?avor scheme [24,25] and has a cross section of 25 fb for mH ≈ 100 GeV. The two main production modes at the Tevatron are therefore gluon fusion gg→H + X and associated production q q →W H +X, q q→ZH +X. ? ? The associated production processes have cross sections known at NNLO in QCD and NLO for the electroweak corrections with a rather small residual theoretical uncertainty that is less than 5% [25,26]. The gluon fusion process gg→H + X is known at NNLO in QCD (in the large top-mass limit) and at NLO in QCD for arbitrary top mass, with an overall residual theoretical uncertainty estimated to be around 10% [27]. All Higgs signals are simulated using pythia [28], and CTEQ5L or CTEQ6L [29] leading-order (LO) parton distribution functions. The signal cross sections are normalized to next-to-next-to-leading order (NNLO) calculations [25,27], and branching fractions from hdecay [30]. 4.2 SM backgrounds The dominant backgrounds to Higgs analyses at low ? mass comprise W/Z+jets, tt, single top, and multijet (instrumental) events. The latter are sometimes referred to as “QCD background”. At high mass, di-boson processes represent the main contribution to the backgrounds.

Arnaud Duperrin

Review of Searches for Higgs Bosons and BSM Physics at the Tevatron - Page 5

CDF Run II Preliminary (1.9 fb )

Events

-1

Number of events

50
Data W+HF Mistag t t (6.7pb),Single top Diboson NonW Higgs (120 GeV) × 10 Background error
8 7 6 5

103

L = 1.7 fb-1 D? Preliminary

W + 2 jets / 2 b-tags

40

102

Data W + jets QCD tt Wbb other WH
115 GeV (x10)

30
10

20

4 3 2 1 0

1
0.5 0.6 0.7 0.8 0.9 1

10

0.4

0

0.2

0.4

0.6

0.8

1

1.2

1.4

0 0

0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 NN output

NN output - 2 tags
Fig. 7. D? ?nal analysis variable distribution (neural network output) used by the associated Higgs boson production search in the W H → ?νb? channel after requiring b two b-tagged jets in the event [43]. The result is shown for an integrated luminosity of 1.7 fb?1 of data. The background expectations and the observed data are shown. The expected Higgs signals, scaled as indicated, is represented for a neural network trained with a Higgs boson mass of mH = 115 GeV.

Fig. 6. Neural network output distribution obtained after ?nal selection in the search for associated Higgs boson production (W H → ?νb? channel) using 1.9 fb?1 of CDF Run b II data [42]. Two of the jets in the event are required to be identi?ed as containing b-quarks (b-tagging). The background expectations and the observed data are shown. The expected Higgs signals, scaled as indicated, is represented for a neural network trained with a Higgs boson mass of mH = 120 GeV. The insert shows a zoom-in the signal region.

For both CDF and D?, the multijet background is estimated from data, usually in orthogonal samples to those used for the analyses. For CDF, backgrounds from other SM processes are generated using the pythia, alpgen [31], mc@nlo [32] and herwig [33] programs. For D?, these backgrounds were generated using pythia, alpgen and comphep [34], with pythia providing parton-showering and hadronization for all the generators. Background processes are normalized using either experimental data or next-to-leading 4.3.1 b-identi?cation: order calculations from MCFM [35]. At low mass, the searches primarily focus on the dominant H→b? decay, which leads to the presence of b b jets for the signal. The sensitivity of the Higgs boson 4.3 Search strategy searches is signi?cantly increased by using a lifetimeAt the Tevatron, the most sensitive channels to search based heavy-?avor tagging algorithm (b-tagging) which for a low mass SM Higgs boson (mH < 135 GeV) are computes a probability for a jet to be light-?avored those from associated production, with W →lν and based on the impact parameters of the tracks in the H→b? or Z→ll or νν and H→b? At high mass, mH ≈ jet. Another method is based on secondary vertex reb, b. 160 GeV, the branching fraction is mainly into W W construction. boson pairs, and the leptonic decays of the W are exFor instance, D? combines in a neural network ploited through gluon-gluon fusion p?→H→W W (?) . p (NN) discriminant [36] several kinematic variables senThere are secondary modes that provide additional sitive to transversely-displaced jet vertices and jet tracks sensitivity. For intermediate masses around 135 GeV, with large transverse impact parameters relative to all branching fractions are below 40%; however, p? the hard-scatter vertices. The NN is trained to idenp →W H →W W W ? →?± ?± and p?→H→γγ are used tify heavy-?avor quark decays and reject jets arising p to strengthen the discovery potential. At the Teva- from light-?avor quarks or gluons. By adjusting the tron, the decay channel p?→H→ZZ (?) does not signif- minimum requirement on the b-tagging NN output, p icantly contribute due to combination of lower branch- a spectrum of increasingly stringent b-tagging operating ratios for H→ZZ and Z→?? in addition to the ac- ing points is achieved, each with a di?erent signal e?ceptance for four leptons. Though both Collaborations ciency and purity. The analyses are usually separated

do intend to add such analysis in the future, this mode has not yet been studied for the current combination. At low mass, a 5% contribution from the addition of the H→τ τ decay mode is included. The CDF experiment contributes to the most recent SM Higgs combination with this new analysis searching for the Higgs bosons decay to a tau lepton pair, in three production channels: gluon fusion, associated production, and VBF (details are given later).

Arnaud Duperrin
×10 3
3

Review - Page 6
×10 4.5 4 3.5 3 2.5 2
3

Events / 0.15

D? preliminary (2.1 fb-1)
Data Top Z+b/c-jets Z+jets(l.f.) W+b/c-jets W+jets(l.f.) Diboson Multijet Hx500 (115 GeV)

Events / 12.00 GeV

D? preliminary (2.1 fb-1)
Data Top Z+b/c-jets Z+jets(l.f.) W+b/c-jets W+jets(l.f.) Diboson Multijet Hx500 (115 GeV)

2.5 2

1.5

1

1.5 1

0.5 0.5 0 0.5 1 1.5 2 2.5

min ?φ(Jets, E )
T

3

3.5

0

50

100

150

200

250

300

DiJet Invariant Mass (GeV)

/ Fig. 8. Distributions of the ?φmin (ET ,jets) (left), the minimum of the di?erences in azimuth between the direction of / ET and the direction of any jet, and of the dijet invariant mass of the two leading jets (right), in the analysis sample before b-tagging for the D? search in the p?→ZH→ν ν b? channel using 2.1 fb?1 of data [46]. The various background p ? b contributions (SM and multijet) are shown. Distributions for a signal with a Higgs boson mass of 115 GeV are also shown, scaled as indicated.

into those where two of the jets are b-tagged with a loose tagging requirement and those where only one jet is tagged with a tight requirement. Typically, the b-tagging tight (loose) operating point is selected such that, for jets with pT of ≈ 50 GeV, 0.5% (1.5%) of the light-?avored jets are tagged while the tagging ef?ciency for b-quark jets is 50% (60%).

4.3.3 Standard model background understanding: One of the major goals of the searches is to ?rst carry out a detailed assessment of the generators used for the simulation of those processes, by confronting them with measurements, which are becoming increasingly more precise as the datasets grow. Monte Carlo simulations, mostly based on ?xedorder matrix elements, are used to extrapolate these measurements into the Higgs signal regions. In order to validate the whole analysis chain, the associated production of vector bosons, W Z and ZZ, can be used. With W Z→?νb? and ZZ→??/νν b? the ?nal states b b, are actually almost identical to those considered in the search for the Higgs boson, up to the mass difference between the Z boson and the Higgs boson. Observation of these reactions will therefore be among the main goals of the coming year, and their detailed analysis will pave the way for a de?nitive calibration of the Higgs boson searches, with a caveat that Z→b? b branching fraction is a factor of 3 or less than the H→b? The next-to-leading order (NLO) ZZ cross secb. tion at the Tevatron is 1.4 ± 0.1 pb [35], an order of magnitude above some of the expected SM Higgs production cross sections. Additionally, this process forms an irreducible background to Higgs searches in the ZH channel. For instance, the CDF Collaboration recently submitted for publication the ?rst measurement at a hadron collider of the cross section for Z boson pair production in the leptonic decay channels with a significance of 4.4 standard deviations based on 1.9 fb?1 of data [38]. The measured cross section is σ(p?→ZZ) = p 1.4+0.7 (stat. + syst.) pb. The D? Collaboration also ?0.6 conducted such a measurement based on 2.2 fb?1 of data. Using the ?nal state decay ZZ→??ν ν , D? ob? serves a signal with a 2.4σ signi?cance and measures a

4.3.2 Advanced analysis techniques:

After kinematic selection and b-tagging, the remaining backgrounds in a Higgs boson search would ideally be due solely to the associated production of a W or Z boson with a pair of b quarks. The Higgs boson would then appear as a b? resonance over a broad continuum. b The signi?cance of a Higgs boson signal is therefore directly related to the mass resolution of a system of two b quark jets, and thus to the jet energy resolution. The dijet mass is however not the only feature which allows discrimination between signal and background. Other, more subtle, di?erences in the kinematic properties of the signal and the backgrounds can be used. Because no single variable provides su?cient discriminating power, advanced analysis techniques have to be used, such as neural networks or decision trees [37]. The matrix element approach, which makes full use of the event properties at leading order and in which there is already experience in the CDF and D? Collaborations, can also be introduced to enhance the discriminating power of, for example, a neural network. The performance of even the most elaborate multivariate analysis, however, critically depends on an accurate understanding of the characteristics of the signal and background processes.

Arnaud Duperrin

Review of Searches for Higgs Bosons and BSM Physics at the Tevatron - Page 7 bosons as possible. The most recent published W H searches have been performed with integrated luminosities of 955 pb?1 for CDF [40] and 440 pb?1 for D? [41]. The latest updates with 1.9 fb?1 from CDF [42] (winter 2008) and 1.7 fb?1 from D? [43] (summer 2007) use similar search strategies. The high-pT electron or muon is required to be isolated with ET (or pT ) greater than 20 GeV and events with more than one isolated lepton are vetoed. Selected events must also display a signi?cant missing transverse en/ ergy (ET > 20 GeV). QCD events with false W signatures are estimated with the data by computing the ratio of isolated to non-isolated leptons in a control region. Both CDF and D? use neural-network discriminants to separate the signal from the SM background events. As an illustration for these searches, Fig. 6 and Fig. 7 show some distributions of the ?nal variables used by the CDF and D? experiments for limit setting. The D? search requires at least one tight b-tagged jet or exactly two loose b-tagged jets in the event, and two b-tagged jets are required in the CDF search. At mH = 115 GeV, the ratio between the expected (observed) cross section limit and the SM value is 8.2 (7.3) for CDF and 9.1 (11.1) for D?.

Double Vertex Tag (Signal Region)
25
CDF Run II Preliminary (1.7 fb )
-1

20

15

Ttbar W+h.f. Z+h.f Single Top WZ/WW ZZ Mistags QCD Bckgnd Err VH*8 (115 GeV) Data

10

5

0

60

80

100

120

140

160

180

200

Missing Et (GeV)

Double Vertex Tag (Signal Region)
18 16 14 12 10 8 6 4 2 0 50 100 150 200 250 300
CDF Run II Preliminary (1.7 fb )
-1

Ttbar W+h.f. Z+h.f Single Top WZ/WW ZZ Mistags QCD Bckgnd Err VH*8 (115 GeV) Data

4.4.2 p?→ZH→ν ν b? p ? b: Triggering on p?→ZH→ν ν b? is more challenging than p ? b on the charged leptons from W or Z decays. This is because only hadronic jets are visible in the ?nal state, which makes it di?cult to distinguish it from standard multijet production via the strong interaction. The distinctive feature is the missing transverse energy carried by the neutrinos from the Z decay. However, standard multijet events can also exhibit missing transverse energy due to ?uctuations in the jet energy measurement by the calorimeter, or to semileptonic decay in heavy ?avor jets. Complex topological triggers have therefore been designed, combining measurements of jet energies and directions, and missing transverse energy. The D? Collaboration has published a result based on 260 pb?1 of data [44] and the CDF Collaboration recently submitted for publication a search corresponding to an integrated luminosity of 1 fb?1 [45]. Both experiments updated these results for the winter 2008 conferences with 2.1 fb?1 [46] and 1.7 fb?1 [47] of data for D? and CDF, respectively. / One of the largest backgrounds in the ET +jets channel involves heavy ?avor multijet production. Although the probability for multijet events to create arti?cial missing energy at a signi?cant level is small, the huge cross section of multijet production renders this background overwhelming at the initial stages of the analysis. Currently, severe selection criteria are used / (mainly ET > 50 GeV) in order to practically eliminate that background, thus introducing substantial ine?ciencies. The normalization and shape of multijet events are obtained from the data to take into account all relevant instrumental e?ects and biases. This multijet control sample is extracted in the data sample

Dijet Mass (GeV/c )
/ Fig. 9. Distributions of the ET (top) and dijet invariant mass (bottom) in the signal region after requiring 2 b-tagged jets for the CDF search in the p?→ZH→ν ν b? p ? b channel using 1.7 fb?1 of data [47]. The expected Higgs signal at mH = 115 GeV is scaled as indicated.

2

cross section σ(p?→ZZ) = 2.1 ± 1.1(stat.) ± 0.4(sys.) p pb [39]. 4.4 Associated production Associated V H production (V = W, Z) can be distinguished from multijet and electroweak backgrounds by exploiting the leptons and/or the missing transverse energy in the ?nal state. 4.4.1 p?→W H→?νb? p b: The ?nal state from p?→W H production, where the p W boson decays leptonically, provides an ideal trigger signature to collect as many of the produced Higgs

Arnaud Duperrin
Events

Review - Page 8

20 18 16 14 12 10 8 6 4 2

CDF II Preliminary



ZH→ l l bb, DT Run IIa D? Preliminary, L=1.10 fb
-1

Data Sum of Backgrounds Signal (m =115 GeV/c2)
H

Ldt = 0.97 - 1.02 fb

-1

102

Data (Single Tag) Backgrounds w/ Alpgen ZH → llbb X 50 (MH = 120 GeV/c ) ZH → llbb X 50 (before MPDF)
2

10

1

10-1

-0.4

-0.2

0

0.2

0.4

0.6

0.8

0

50

100

150

200

250
2

NN Output

1

1.2

Mjj (GeV/c )
Fig. 10. Distributions of the dijet invariant mass in the signal region after requiring 2 b-tagged jets for the CDF search in the p?→ZH→??b? channel using ≈ 1 fb?1 of data p b [48]. A correction (MPDF) is applied to reassign missing / energy to the jets since the dominant source of ET are jet energy mismeasurement. The expected Higgs signal at mH = 115 GeV is scaled as indicated.

Fig. 11. Distributions of the neural net output variable after requiring 2 b-tagged jets for the D? search in the p?→ZH→??b? channel using 1.1 fb?1 of data [49]. The p b total predicted background, data and expected Higgs signal at mH = 115 GeV are shown.

/ where the ET is aligned with the second jet. The distributions of the minimum of the di?erences in azimuth / between the direction of the ET and the direction of any jet, and the dijet invariant mass of the two leading jets, are shown in Fig. 8 for the D? experiment. It is seen that the combination of the multijet and SM background provides a good description of the data in the pre-tag sample. Advantage of the large branching fractions for H→ b? is used by requiring the two leading jets to be bb / tagged. Figure 9 shows the distributions of ET and dijet invariant mass for the CDF analysis after all selection requirements are imposed. In the case of W H→ ?νb? production where the primary lepton from the W b boson decay falls outside of the detector acceptance / b and is not identi?ed, the ?nal state W H→? νb? is the / b same as the ZH→ν ν b? The W H→? νb? events con? b. / tribute to signi?cantly enhance the ET +jets analysis sensitivity. Finally, a boosted decision tree technique was used for the D? search and a NN discriminant for the CDF search to calculate the cross section limit. For a 115 GeV Higgs boson mass and requiring two b-tagged jets in the event, the observed/expected limits on the cross section of combined ZH→ν ν b? and ? b / b W H→? νb? production are 8/8.3 (7.5/8.4) times larger than the SM value for CDF (D?). 4.4.3 p?→ZH→??b? p b: Searches for the Higgs boson from the process p?→ZH p →??b? in both e+ e? and ?+ ?? channels have been b carried out by CDF [48] and D? [49] in 1 fb?1 of

data. The D? experiment has published a result based on 0.45 fb?1 [50]. These channels have a small background of mostly Z+jets events due to the requirement of two leptons and a Z mass constraint, but suffer from a smaller Z branching fraction. To maintain signal e?ciency and improve discrimination, the experiments employ neural networks trained to separate ZH events from the main Z+jets background and the ? kinematically di?erent tt background. To improve sensitivity, the data are divided into single and double btagged channels (double b-tagged only for CDF); the results are shown in Fig. 10 and Fig. 11. The expected (observed) limits from the data as a ratio compared to the expected SM cross section are 20.4 (17.8) for the D0 analyses, and 16 (16) for the CDF search, at mH = 115 GeV. 4.4.4 p?→W H→W W W (?) →?± ?± : p In the SM, the Higgs boson predominantly decays to a W W (?) pair for Higgs masses above 135 GeV. Although the scenario W H→W W W (?) →?± ?± + X is not the most sensitive search for high masses, this process provides a unique experimental signature with two like-charge leptons from W decays. Furthermore, in some scenarios with anomalous couplings, such as fermiophobic Higgs models, the branching fraction to W W (?) may be close to 100% for Higgs masses down to ≈100 GeV [51,52,53]. The D? Collaboration has searched for fermiophobic Higgs (hf ) and published [54] results with 380 pb?1 in the ee channel, 370 pb?1 in the e? channel, and 360 pb?1 in the ?? channel, with the variations related primarily to di?erent trigger requirements. Upper limits are set on σ(p?→W hf ) × p Br(hf →W + W ? ) between 3.2 and 2.8 pb for Higgs boson masses from 115 to 175 GeV at 95% C.L. Recently,

Arnaud Duperrin
D? Run IIb Preliminary
entries

Review of Searches for Higgs Bosons and BSM Physics at the Tevatron - Page 9
e+ eL=1.2/fb
D? Run II Preliminary
data H160 → WW× 10

Events

105 104 103 10
2

L = 1.2 fb
Data Z/ γ *→ l l
+ -

-1

105 104

WW/WZ/ZZ W → lν Multijet

Z→ee

103 10
2

tt (M =170)
t

gg→ H, qq→ qqH (M =160)
H

Diboson

10 1

W+jets/γ

10 1 10-1 10-20 20 40 60 80 100 120
T

QCD

10

-1

ttbar

0

0.5

1

1.5

2

2.5

3

3.5

?φ(e,e)

4

140

Missing E [GeV]

/ Fig. 12. Distributions of the opening angle ?φe1 e2 for the ee system (left) and ET for the ?? system (right) at ′ (?) pre-selection level for the D? search in the p?→H→W W →?ν? ν channel using 1.2 fb?1 of data [61]. The expected p Higgs signal at mH = 160 GeV, the predicted background, and the data events are shown. Table 2. The numbers of signal events expected for a Higgs boson mass mH = 160 GeV, events expected from SM backgrounds, and data events observed, for the CDF experiment using 2.4 fb?1 of data [59]. The SM Higgs boson production and decay are assumed to be gg → H → W W ? → l+ l? νν, where l± = e, ?, or τ . The ?nal state e trk (? trk) require an electron (a muon) and an additional track (trk).

Category ee e? ?? e trk ? trk Total

Higgs (mH = 160 GeV) 1.7 3.8 1.6 1.6 1.0 9.5

WW 55.1 131.7 43.4 45.5 24.8 300.3

WZ 6.4 3.9 4.9 3.1 2.0 20.6

ZZ 7.1 0.4 5.8 2.9 2.0 18.2

? tt 3.6 8.7 3.3 3.3 1.9 20.8

DY 33.6 27.4 23.1 13.1 7.1 104.0

Wγ 33.6 29.4 0.0 8.0 1.5 72.3

W +jets 29.5 34.1 5.2 13.3 7.9 90.0

Total 169±14 235±21 86±8 89±7 47±4 626±54

Data 171 240 83 107 60 661

CDF presented a preliminary result using 1.9 fb?1 of data [55]. This search expects 0.46 (0.19) event for a fermiophobic Higgs boson mass of 110 (160) GeV, assuming SM production cross section. The expected background is 3.23 ± 0.69 events, while 3 events are observed in the data. From these results, CDF sets limits of 2.2 pb for mhf = 110 GeV and 1.4 pb for mhf = 160 GeV at 95% C.L. For these searches, the main physics background is W Z →?ν?? production. The irreducible physics background, which comes from non-resonant W W W triple vector boson production has a very low cross section ? (as does tt). As the channel involves two neutrinos in the ?nal state, the reconstruction of the Higgs mass is not feasible and the potential Higgs signal appears as an excess in the number of observed events with two like-charge leptons over the predicted SM background. In the absence of such an excess, upper cross section limits are set by the CDF [55] (D? [56]) search with 1.9 (1.1) fb?1 of about 33 (20) times above the SM Higgs boson cross section at mH = 160 GeV.

4.5 Gluon fusion The largest production cross section for the whole Higgs mass range of interest is the gluon fusion process due to the large top Yukawa couplings and the gluon densities. At the Tevatron, however, the gluon fusion process becomes relevant with a clear experimental signature only at high mass (mH ≈ 160 GeV), where the branching fraction is mainly into W W boson pairs leading to a favorable ?nal state with two leptons and two neutrinos. At low mass (mH 135 GeV), due to the large branching fraction of the Higgs boson into b? the gluon fusion Higgs production mode cannot be b, disentangled from the multijet background. 4.5.1 p?→H→W W (?) : p At the Tevatron, the decay mode p?→H→W W (?) prop vides the largest sensitivity for the SM Higgs boson search at a Higgs boson mass of mH ≈ 160 GeV. Upper limits on the cross section times branching fraction ′ ′ in the leptonic decay modes H→W W ? →?? (?, ? =

Arnaud Duperrin
Events

Review - Page 10

CDF Run II Preliminary
HWW ME+NN MH = 160 [GeV/c ]
2



107 10 10 10 10
6

L = 2.4 fb
High S/B HWW Wj Wγ tt WZ ZZ DY WW Data

-1

H→ γ γ -1 D? Preliminary, L=2.30 fb

Data Sum of Backgrounds Signal (m =115 GeV/c2)
H

5

102

4

10

3

102

1

10 1 10-1

10-1

10

-2

60

80

100

120

140

160

-1

-0.8

-0.6

-0.4

-0.2

0

0.2

0.4

0.6

0.8

1

γ γ Inv. Mass (GeV/c2)

180

200

220

240

NN Output

Fig. 13. Neural network template used as a ?nal discriminant to search for the SM Higgs boson in the ′ p?→H→W W (?)→?ν? ν decay channel using 2.4 fb?1 of p CDF data [59]. The signal is shown for mH = 160 GeV.

Fig. 14. Final variable distributions (diphoton invariant mass) for the D? Higgs search analysis in p?→H→γγ ?nal p state using 2.3 fb?1 of Run II data [63]. The total predicted background, observed number of event and expected Higgs signal at mH = 115 GeV are shown.

e, ?, τ ) from previous Run IIa data have already been published by the CDF (D?) Collaboration with 360 pb?1 [57] (325 pb?1 [58]). The most recent data available from Run IIb have been recently analyzed and preliminary results have been presented by CDF [59] and D? [60,61] using 2.4 fb?1 and 2.3 fb?1 of data, respectively. In all ?nal states, two isolated leptons of opposite sign originating from the same primary vertex are required. The background is dominated by Z/γ ? and multijet events in which the leptons are typically back-to-back. It is therefore suppressed by requiring some missing transverse energy and with a cut on the opening angle ?φ?? which is smaller for the signal than for the background due to the spin-correlation between the ?nal state leptons in the decay of the spin-0 Higgs / boson. Figure 12 shows the ?φ?? and the ET distributions at pre-selection level for the D? search. After ?nal selection, the CDF search ?nds 661 candidates with an expectation of 626 ± 54 background events and 9.5 signal events for a SM Higgs at mH = 160 GeV. Table 2 provides a detailed breakdown of the signal and background contributions in each ?nal state. The presence of neutrinos in the ?nal state prevents reconstruction of the Higgs boson mass. In order to maximize the signal sensitivity, a combined matrix element method and neural network approach are utilized to distinguish signal from background processes. An example of neural network template is shown in Fig. 13 for mH = 160 GeV. The median expected 95% C.L. limit at a Higgs mass of 160 GeV is 2.5+1.0 ?0.7 times the SM prediction at NNLL, while the observed limit is 1.6 times the SM prediction. To improve the separation of signal from backgrounds, a neural network is also used for the D? search in each of the three di-lepton channels. The D? expected and observed upper limits relative to the SM Higgs boson

cross section prediction are 2.4 and 2.1, respectively, for mH = 160 GeV.

4.5.2 p?→H→γγ: p In the SM, the diphoton decay of the Higgs boson are suppressed at tree level and the branching fraction for this decay is 0.22% for a 130 GeV Higgs boson mass. However, in some models beyond the SM, this decay can be enhanced signi?cantly; some examples can be found in Refs. [51,52,53] and section 6 of this review. The D? experiment has recently submitted for publication a search for a narrow resonance decaying into two photons using 1.1 fb?1 of data [62]. This result has been updated with 2.3 fb?1 [63] and the SM Higgs is used as a possible signal model to set upper limits on the production cross section times branching fraction (H→γγ) for di?erent assumed Higgs bosons masses. There are three major sources of background. The ?rst source comes from Drell-Yan events where both electrons are misidenti?ed as photons due to tracking ine?ciencies, and is estimated with Monte Carlo simulations. The second source is from direct QED diphoton events and is also estimated using simulation. Finally, the background from γ+jet and jet+jet events, where the jets are mis-identi?ed as photons, is obtained from data. The invariant mass of the two photon candidates in the interval 50 GeV < mγγ < 250 GeV, shown in Fig. 14, is used as input to the limit setting program. This search contributes to improve the global sensitivity in the di?cult region around mH ≈ 130 GeV, with a σ × Br ratio to SM of about 45.

Arnaud Duperrin

Review of Searches for Higgs Bosons and BSM Physics at the Tevatron - Page 11

95% CL Limit/SM

10 2

Tevatron Run II Preliminary, L=1.0-2.4 fb

-1

LEP Limit

10

Tevatron Expected Tevatron Observed ±1σ CDF Exp ±2σ D? Exp

1

SM
April 9, 2008

110 120 130 140 150 160 170 180 190 200 mH(GeV/c2)
Fig. 15. The new Tevatron combination [66] presented at the winter 2008 conferences showing the upper bound on the SM Higgs boson cross section as a function of the Higgs boson mass. The contributing production processes include associated production (W H → ?νb? ZH → ??/ννb? W H → W W + W ? ) or gluon fusion (H → W + W ? , H→γγ) or b, b, vector boson fusion, and H→τ τ produced in several modes. The limits at 95% con?dence level (C.L.) are shown as a multiple of the SM cross section. The solid curve shows the observed upper bound, while the dashed curves show the expected upper bounds assuming no signal is present. Analyses are conducted with integrated luminosities ranging from 1.0 fb?1 to 2.4 fb?1 recorded by each experiment. The bands indicate the 68% and 95% probability regions where the limits can ?uctuate in the absence of signal. The expected upper limits obtained from the CDF and D? experiments are also shown. The region excluded by the LEP experiments is also shown [20].

4.6 H + X→τ + τ ? + 2 jets The CDF Collaboration recently conducted a search with about 2 fb?1 of data using the τ decay mode of the Higgs boson [64]. Several processes are considered: Higgs production in association with a vector boson (W/Z), in which the vector boson decays into 2 jets (Br are 67/70% for W/Z), vector boson fusion production in which the 2 jets coming from the proton and antiproton tend to have a large rapidity value and, ?nally, gluon fusion production. The analysis requires at least 2 jets, one hadronic tau with pT > 15 GeV and one leptonic tau identi?ed as an isolated central electron (or muon) with pT > 10 GeV. In this analysis, the ?nal variable for setting limits is a combination of several neural network discriminants.

The expected (observed) sensitivity is roughly about 50% (30-40%) compared to that of searches for associated Higgs production. The expected cross section limit is 24 times the SM cross section for mH = 120 GeV. Combined with all other analyses, this result improves the global low mass Higgs search sensitivity. 4.7 Combined upper limits All individual channels of both Tevatron experiments are combined to maximize the sensitivity to the Higgs boson. The combination of D? results based on 0.44 fb?1 of data has been published [41]. All new results included in this review have been used for the combination presented at the winter 2008

Arnaud Duperrin

Review - Page 12

95% C.L. Limit / σ(SM)

-1 D? Preliminary, L=1.1-2.3 fb 95% C.L. Expected Limit / σ(SM)

102

ZH→llbb: 1.1 fb-1 ZH→ν ν bb: 2.1 fb-1 WH→lν bb: 1.7 fb-1 WH→W W+W : 1.1 fb-1 + H→W W : 2.3 fb-1 H→γ γ : 2.3 fb-1 DZero Combination

10

1

Standard Model = 1.0

110 120 130 140 150 160 170 180 190 200 mH (GeV/c2)
Fig. 16. Expected 95% C.L. cross section ratios for the individual W H/ZH/H, H→b? b/γγ/W + W ? analyses in the ?1 100 GeV < mH < 200 GeV mass range for D? alone using 1.1-2.3 fb of data [68].

conferences. These results have an improved sensitivity compared to the previous Tevatron combination presented in December 2007 [65]. The new Tevatron combination (21 April 2008, see Ref. [66]) includes all results from searches for a SM Higgs boson produced in association with vector bosons (p? → W H → ?νb? p b, p? → ZH → ν ν b? p? → ZH → ??b? and p? →W H p ? b, p b p → W W W ? → ?± ?± ) or through gluon-gluon fusion (p?→H→W W (?) and p?→H→γγ) or vector boson fup p sion, and H→τ τ produced in several modes, in data corresponding to integrated luminosities ranging from 1.0-2.4 fb?1 at CDF [67] and 1.1-2.3 fb?1 at D? [68]. This is the ?rst time that searches for Higgs bosons decaying to two photons or two tau leptons are included in the combination. 4.7.1 Method used for the combination To simplify their combination, the searches are separated into twenty nine mutually exclusive ?nal states (thirteen for CDF, sixteen for D?). In addition, several types of combinations are performed using the Bayesian [67] and Modi?ed Frequentist [69] approaches to check that the ?nal result does not depend on the details of the statistical method used for the combination. The Modi?ed Frequentist approach is sometimes called the LEP CLs method, which is based on the log-likelihood ratio (LLR) test statistic LLR(n) = ?2 ln(Q), e?(s+b) (s + b)n e?b (b)n / , n! n! where s and b are the expected numbers of signal and background events while n is the number of data Q = L(s + b)/L(b) =

events. For all channels, the LLR values per bin are added in order to use the shape information of the ?nal discriminating variable and to combine the di?erent channels. In addition, the CLs method has been extended to involve a ?t of the nuisance parameters for each event, which maximizes the sensitivity in the context of large background, small signals and large uncertainties [70]. Both CLs and Bayesian methods use Poisson likelihoods and agree within ? 10%. They rely on distributions of the ?nal discriminants like NN output, matrix-element likelihoods, or dijet mass and not only on the event counting. The uncertainty on the expected number of events as well as the shape of the discriminant variables are included in the systematic uncertainties. 4.7.2 Systematic uncertainties The correlations of systematic uncertainties between channels, rates and shapes, signals and backgrounds, within and between experiments are considered. Many sources are measured using data. Sometimes they are large but correspond to backgrounds with small contribution. Furthermore, the uncertainties are constrained by ?ts to the nuisance parameters and do not necessarily a?ect the result signi?cantly. The following dominant sources of systematic uncertainties are taken into account in deriving the ?nal results. Each experiment has a luminosity uncertainty of ≈6%, of which ≈4% is correlated. Depending on the channel, the range of uncertainties from SM cross sections used to normalize the simulation vary between 4% and 20%. The uncertainty needed to describe heavy ?avor (HF) fractions in W/Z+jets and the e?ect of the NLO HF cross section normalisation

Arnaud Duperrin

Review of Searches for Higgs Bosons and BSM Physics at the Tevatron - Page 13
10
6

are evaluated to be 20%-50%, depending on how the background is estimated, from data or simulation. The scale factor used to adjust the b-tagging e?ciencies in the simulation results in 4%-25% uncertainties, depending on the number of tagged jets required. The uncertainty from the jet energy scale ranges between 1% and 20%, depending on the background process. The uncertainties resulting from the modelling of QCD multijet background are dominated by statistics in the samples from which the estimates are derived and can reach 30%. The uncertainties from lepton identi?cation and reconstruction e?ciencies ranges from negligible to 13%. Finally, the uncertainty from the trigger e?ciency is less than 5%. 4.7.3 Combined results The cross section limits on SM Higgs boson production σ × Br(H → X) obtained by combining CDF and D? results with up to 2.4 fb?1 of data [66] are displayed in Fig. 15. The result is normalized to the SM cross section, where a value of one would indicate a Higgs mass excluded at 95% C.L. The observed (expected) upper limits are a factor of 3.7 (3.3) higher than the expected SM Higgs boson cross section at mH = 115 GeV and 1.1 (1.6) at mH = 160 GeV. The combined CDF and D? result represents a 40% improvement in expected sensitivity over each single experiment. The observed (expected) limits on the SM ratios are 5.0 (4.5) for CDF and 6.4 (5.5) for D? at mH = 115 GeV, and 1.6 (2.6) for CDF and 2.2 (2.4) for D? at mH = 160 GeV. The sensitivity of each individual analysis from D? alone is given in Fig. 16. As shown in this ?gure, the associated production and gluon fusion processes play an important complementary role to improve the sensitivity for the intermediate mass region around mH = 135 GeV, which is the most di?cult mass to probe at Tevatron.

10

5

Tevatron, √s = 1.96 TeV max mh , tanβ = 40 ggΦ

h H A

Φ production cross section [fb]

10

4

10

3

(bb)Φ

10

2

10

1

W/ZΦ 10
0

qqΦ ttΦ

10

-1

100

150

200

250

MΦ [GeV]

Fig. 17. MSSM Higgs boson production cross section as function of mφ (φ = h, H, A) for various production modes at tan β = 40 in the mmax scenario [21]. h

With the Tevatron running well, up to ≈ 6 SM Higgs bosons events per day are produced per experiment, and the CDF and D? Collaborations constantly improve their ability to ?nd them. Combining CDF and D?, about 4 fb?1 could be su?cient to exclude the SM Higgs boson for mH = 115 GeV and mH = 160 GeV at 95% C.L. Assuming 7 fb?1 of data analyzed by the end of the Tevatron running, all SM Higgs boson masses -except for the real mass value- could be excluded at 95% C.L. up to 180 GeV.

5 Higgs bosons in the MSSM

In the minimal supersymmetric extension of the standard model, two Higgs doublets are necessary to cancel triangular anomalies and to provide masses to all par4.8 SM Higgs boson prospects ticles. After electroweak symmetry breaking, the MSSM It is expected that the sensitivity needed to reach a predicts 5 Higgs bosons. Three are neutral bosons: h, 95% C.L. limit exclusion, at a mass mH ≈ 160 GeV, H (scalar) and A (pseudo-scalar), and two are charged will be reached by the end of 2008 by the combined bosons: H + and H ? . An important prediction of the MSSM is the theoTevatron experiments. Since the ?rst CDF and D? combination in 2006, a retical upper limit mh 135 GeV on the mass of the lot of progress has been made, resulting in better sensi- lightest Higgs boson once the radiative loop correctivity in all channels (i.e., neural network b-tagger, im- tions have been taken into account [71,72]. All other proved selections, matrix-element techniques). Many relations between the Higgs masses and coupling are of these improvements led to an equivalent gain of also signi?cantly modi?ed by the radiative corrections, more than twice the luminosity, which means that the which are dominated by the top- and stop-loop contrisensitivity has progressed faster than one would expect butions [71,73]. For large masses of the pseudo-scalar boson A, the light scalar Higgs becomes SM-like. The from the square root of the luminosity gained. Recent projections in sensitivity have been made main di?erence between the MSSM Higgs bosons and the based on achievable improvements of the current anal- SM Higgs boson is the enhancement of the production yses. These include progress on the existing improved cross section by a factor proportional to tan2 β, where lepton identi?cation e?ciency, heavy-?avor taggers and tan β = v2 /v1 is the ratio of the vacuum expectation b-tagging enhancement from the D? layer L0, upgraded values associated with the two neutral components of trigger acceptance, increased usage of advanced anal- the scalar Higgs ?elds. In contrast to the SM Higgs boysis techniques, jet resolution optimization, reduced son, the widths of the MSSM Higgs bosons do not exceed several tens of GeV in most of the scenarios. systematics, and inclusion of additional channels.

Arnaud Duperrin
4 3.5 3 2.5

Review - Page 14

g

b h

q

b h

g
2 1.5 1 0.5 0

? b

q ?

? b

Fig. 19. Feynman diagrams contributing to the LO gg → b? and q q → b? MSSM Higgs boson production in associbh ? bh ation with bottom quarks.
LEP excluded Theoretically inaccessible

90

100

110

120

130

140

Fig. 18. Scan of the lightest Higgs boson mass versus ?χ2 derived from precision electroweak measurements in the context of a constrained MSSM model. The band around the ?χ2 curve represents the total theoretical uncertainty from unknown higher-order corrections and the dark shaded area on the right is theoretically inaccessible. The top mass mt = 170.9 ± 1.8 was used for this analysis [78].

is the gluon fusion process (2) where only the τ + τ ? mode is promising due to the overwhelming b? backb ground. The search strategy for charged MSSM Higgs bosons depends on their mass. For masses mH ± < mt ? mb , the charged Higgs can be produced in the decay of the top quark t→bH + , which, in addition to the SM t→bW + decay, leads to the relevant production mode at the Tevatron: bW p?→tt→bH +? ? . p ? The charged Higgs may decay to a variety of channels, with H + →τ + ντ dominating for large values of tan β. For values of the charged Higgs mass larger than the top mass, the dominant mode is charged Higgs production in association with a top and a bottom quark. 5.2 Benchmark scenarios

At tree level, only the mass mA and tan β are necessary to parameterize the Higgs sector in the MSSM. For tan β > 1, decays of h and A to b? and τ + τ ? pairs b are dominant with branching fraction of about 90% and 8%, respectively. Although the branching fraction into τ ’s is much smaller than the branching fraction into b’s, the τ mode results in a much cleaner signature than the b mode, as the latter su?ers from a huge heavy-?avor multijet background which is poorly modeled by simulation. Although most of the experimental searches at Tevatron assume CP conservation (CPC) in the MSSM sector, CP-violating (CPV) e?ects can lead to sizable differences for the production and decay properties of the Higgs bosons compared to the CPC scenario [74]. An observation of a new CPV mechanism may yield insight into the observed abundance of matter over anti-matter in the universe.

The choice of mechanism for mediating SUSY breaking and of the soft SUSY breaking terms governs the main phenomenological features of SUSY models. However, more than one hundred free parameters remain in the MSSM, rendering a complete scan virtually impossible. Several benchmark scenarios with simplifying assumptions have been therefore developed to interpret the experimental results. The preliminary limits from CDF and D? are available in the (tan β,mA ) plane and are usually summarized for two SUSY scenarios [75]. The mmax scenario h is designed to maximize the allowed values of mh and 5.1 Search strategy therefore yields conservative exclusion limits. The noAt the Tevatron, CP invariance is assumed for the mixing scenario di?ers by the value (set to zero) of the searches. Both experiments have presented results on parameter Xt which controls the mixing in the stop searches for neutral Higgs bosons in the two most promis- sector, and hence leads to better limits. Moreover, if one demands that the values of the ing ?nal states: bottom and τ Yukawa couplings remain in the perp?→b? p bφ(h/H/A)→b? ? bbb, (1) turbative regime up to energies of the order of the + ? p?→φ(h/H/A)→τ τ . p (2) uni?cation scale, the region tan β ? 50 in the MSSM is theoretically disfavoured [21]. In recent studies [76], The ?rst process (1) corresponds to a neutral Higgs negative values of the Higgsino mass parameter (?) are boson decaying into b? and produced in association also disfavoured. b with bottom quarks. The fourth b is not required in The MSSM Higgs production cross section is shown the search, since a large fraction of the cross section in Fig. 17 for tan β = 40 in the mmax scenario. At large h produces a b-jet that does not pass the jet ET thresh- tan β, the pseudoscalar A boson becomes degenerate old. The second topology investigated at the Tevatron with either the light (h) or heavy (H) scalar bosons

Arnaud Duperrin
600 500 400 300 200

Review of Searches for Higgs Bosons and BSM Physics at the Tevatron - Page 15
mh max, ?=-200 GeV no mixing, ?=+200 GeV

Pairings / [10 GeV/c2]

tanβ

D? data background

140
-1 D?, L=1fb gb → bφ

tanβ

D?, L=1 fb -1
a) 3 jets exclusive
High-mass D

140
-1 D?, L=1fb gb → bφ

120

120

heavy flavor

Excluded at LEP

80

80

100
60

60

40 30 20 10 0 -10 -20 -30 -40

40

excluded area expected limit

Excluded at LEP

100

100

40

excluded area expected limit

20

20

80

100

120

140

160

180

200

220

80

100

120

140

160

180

200

220

50

100

150

200

250

300

350

400

mA [GeV/c2]

mA [GeV/c2]

Mbb [GeV/c2]
Fig. 20. Invariant mass for the high-mass likelihood region for the exclusive three-jet sample used to search for p?→bφ(h/H/A)→bb? + X in 1 fb?1 of D? data [85]. The p b data are compared to the sum of total background processes (solid line) after all selections. The shaded region represents the heavy ?avor component (b? b? c?b). The bb, bc, c ratio between the data and the total background expectation is also shown.

Fig. 21. D? observed and expected 95% C.L. limits on tan β as a function of mA using 1 fb?1 of data [85], assuming tan2 β cross section enhancement. The e?ect of the Higgs width is included. The results are given for two scenarios: mmax with ? = ?200 GeV, and no-mixing with h ? = +200 GeV. The width of φ is larger than 70% above tan β = 100 in the mmax scenario with ? = ?200 GeV. h The exclusions from LEP are also displayed [77].

and the bottom-Higgs coupling is enhanced. A production cross section in the 10 pb range for the (bb)φ process is expected and could be observed at Tevatron. Direct searches at LEP have placed lower mass limits on both the lightest scalar and pseudoscalar Higgs bosons at mh,A > 93 GeV at 95% C.L. [77]. Similarly to the statistical analysis of precision electroweak measurements for the SM Higgs boson [19], a ?t is performed in the context of a constrained MSSM model [78]. The result is given in Fig. 18 as a one parameter scan in the lightest Higgs boson mass. The predicted value mh = 110+8 (exp.) ± 3 (theo.) GeV ?10 agrees with the direct experimental lower limit from LEP of 114.4 GeV [20] and the upper theoretical bound. 5.3 MSSM neutral Higgs bosons 5.3.1 p?→bφ(h/H/A)→bb? + X p b At tree level (see Fig. 19), the cross section [21,79,80] for production of MSSM neutral Higgs bosons in association with bottom quarks is almost entirely dominated by the process gg→b? with only a small contribution bh, from qq→b? bh. A search for p?→bφ(h/H/A)→bb? + X has been p b previously published by D? based on 260 pb?1 [81]. The results have been updated with 880 pb?1 by the D? Collaboration [82] and 980 pb?1 by the CDF Collaboration [83]. For the winter 2008 conferences, CDF has presented a result with 1.9 fb?1 of data [84]. The D? Collaboration has just released for publication an improved analysis based on 1 fb?1 of data [85]. In this analysis, CDF and D? search for an event signature of at least three b-jets with pT greater than

15 GeV. The events are triggered by using silicon tracking and jet requirements. The dijet mass spectrum of the two leading jets is used to separate the Higgs signal from background events. A combination of data and simulation is used to model the background shape. The background in the three-tag sample is essentially all QCD heavy ?avor multijet production. The sample consists of a mix of events: at least two real b-jets with the additional tagged jet being any of a mistagged light jet (≈ 30% are b? bj events where j denotes a light parton: u, d, s quark or gluon), a c-tag (≈ 20% are b? bc+bc? events), or another c b-jet (≈ 50% are b? events). In the three-jet sample, bb the double b-tagged events are found to be predominantly made of two real b-jets. This data sample of two b-tagged jets is exploited to predict the expected triple b-tagged background shape. Both CDF and D? use only the shape, and not the normalization, of the ?nal discriminating variable. All Higgs signal events are simulated using the leading order pythia [28] event generator. The cross section is corrected using next-to-leading order calculations from MCFM [35] for the Higgs+b process. In addition, D? corrects the signal acceptance to NLO. Weights obtained with MCFM are applied to the signal samples as function of pT and η of the leading b-jet which is not from the decay of the Higgs boson. A likelihood discriminant (D) based on six kinematical variables built from the two leading jet-pair combinations is used by the D? search to separate the signal from the background. The invariant mass distribution for the exclusive three-tag sample is shown in Fig. 20 for the high-mass optimized likelihood cuts. To further increase the sensitivity, the analysis is also optimized in the four-jet and ?ve-jet exclusive samples.

Arnaud Duperrin

Review - Page 16

tanβ

200 180 160 140 120 100 80 60 40 20

95% C.L. upper limits

CDF Run II Preliminary (1.9/fb)

mh scenario, ? = -200 GeV Higgs width included

max

expected limit 1σ band 2σ band observed limit 160 180 200
2

0 100

120

140

mA (GeV/c )
Fig. 22. The MSSM exclusion limit at 95% C.L. obtained by the CDF experiment with 1.9 fb?1 of data on searches for neutral Higgs bosons produced in association with bottom quarks and decaying into b? projected onto the (tan β,mA ) b, plane assuming standard model cross section times branching fraction (90%) with tan2 β enhancement [84]. The error bands indicate the ±1σ and ±2σ range of the expected limit.

The CDF search uses a binned maximum-likelihood ?t of two-dimensional templates in the mass of the two leading jets versus a variable sensitive to the ?avor of the jet (based on the mass of the tracks forming the displaced vertex in the jets). The event selection e?ciency varies as a function of the mass of the Higgs boson and is typically below 1%. The results have been interpreted in the context of MSSM models since no signi?cant excess has been observed. Limits are placed on tan β versus the pseudoscalar mass mA . The D? and CDF exclusion contours, shown in Fig. 21 and Fig. 22, respectively, are based on the following approximate formula [86]: σ(b? × BR(φ → b? = bA) b) tan2 σ(b? SM (1+? β 2 × (1+?9 )2 +9 , bA) )
b b

Fig. 23. Partially reconstructed ditau mass (Mvis = p / pT ? + pT τ + ET ) from the CDF search for neutral MSSM Higgs boson production in the τ + τ ? ?nal state using 1.8 fb?1 of data [90]. Data (points with error bars) and expected backgrounds (?lled histogram) are compared. The expected contribution from a signal at mA = 140 GeV is shown.

where σ(b? SM denotes the value of the correspondbA) ing SM Higgs boson production cross section for a Higgs boson mass equal to mA . The dependence of the exclusion bounds in the (tan β,mA ) plane on the parameters entering through the most relevant supersymmetric radiative corrections has been investigated. The loop effects, incorporated into the ?b parameter in the formula above, are discussed in Ref. [21]. The bottom line is that their inclusion can enhance the cross section by ≈ tan2 β depending upon the MSSM scenario and significantly modify the bounds obtained. Negative values of ? will result in stronger limits on tan β since the ?b parameter is proportional to the product of tan β and ?. In addition, CDF and D? take into account the e?ect of the Higgs boson width which is calculated with feynhiggs [72] and included in the simulation as a function of the mass and tan β by convoluting a

relativistic Breit-Wigner function with the NLO cross section. Currently the interpretation of these results within the MSSM framework is carried out using the program feynhiggs. The cross section of feynhiggs are based on a rescaling of the SM cross section by the corresponding MSSM factors of the Yukawa couplings. In future version of these analyses, comparisons with exact NLO calculations of the MSSM cross section for gg→ Higgs should be considered using, for instance, the higlu program [87]. In the mmax scenario with ? negative, the enhanced h production through loop e?ects allows exclusion of tan β values greater than 60-100 over the mass range 90210 GeV for mA . The observed limits are within 2 standard deviations of the expectations over the mass region from 90 to 210 GeV, with the largest excess occurring around 160 GeV and 180 GeV in the CDF and D? Collaboration searches, respectively. 5.3.2 p?→φ(h/H/A)→τ + τ ? p The channels with τ + τ ? ?nal states have smaller signal branching fractions, but the searches do not su?er from the large multijet backgrounds that a?ect φ→b? b. In addition, compensations between large corrections in the Higgs production and decay reduce the impact of radiative corrections [21]. The published Run II CDF [88] (D? [89]) results use 310 (348) pb?1 of data. The CDF Collaboration

Arnaud Duperrin

Review of Searches for Higgs Bosons and BSM Physics at the Tevatron - Page 17

No-mixing, ? = +200 GeV

tan β

100 90 80 70 60 50 40 30 20 10 0 100 120 140

-1 D?, 1.0 fb

Observed limit Expected limit LEP 2
160 180 200 220 240

MA (GeV)
Fig. 24. MSSM neutral Higgs boson preliminary results in the p?→φ(h/H/A)→τ + τ ? channels using 1.8 fb?1 of CDF p data [90]. The excluded regions in the (tan β,mA ) plane are shown for ? > 0. The Tevatron excluded domains in the mmax and no-mixing scenario are similar. Also shown are h the regions excluded by LEP for these two scenarios [92]. Fig. 25. D? MSSM exclusion limits at 95% C.L. obtained with 1 fb?1 of data on searches for neutral MSSM Higgs bosons decaying to tau pairs [91]. The (tan β,mA ) plane is shown for the no-mixing scenario. The excluded region at LEP is also represented [77].

has recently released a new preliminary analysis with 1.8 fb?1 [90]. The D? Collaboration has just submitted for publication the result corresponding to 1 fb?1 of data [91]. Both CDF and D? searches for inclusive production of neutral MSSM Higgs bosons are performed in three ?nal states: τe τh , τ? τh , and τe τ? , where τe , τ? , and τh are notations which stand for τ → eνe ντ , τ → ?ν? ντ , and τ → hadrons ντ , respectively. The decay products in τh appear as narrow jets with low track and π 0 multiplicity. The dominant and irreducible background in the ?nal sample of selected events is from Z/γ ? production with subsequent decays to τ pairs. Other sources of backgrounds are W +jets, di-bosons, and fake jets. The D? search uses neural networks to improve tau lepton identi?cation. These neural networks make use of input variables that exploit the tau signature such as longitudinal and transverse shower shapes and isolation in the calorimeter and the tracker. The CDF search probes for a possible Higgs signal by using a binned likelihood ratio of the partially reconstructed mass of the ditau system (mvis ), de?ned as the invariant mass of the visible tau decay prod/ ucts and the ET . Figure 23 shows mvis in the τ + τ ? ?nal state based on 1.8 fb?1 of data collected by the CDF experiment. Since the data are consistent with a background only observation, limits are derived on the cross section for Higgs boson production times the branching fraction into tau leptons. The background contributions are allowed to ?oat within limits set by Gaussian constraints corresponding to the systematic uncertainties. The corresponding excluded regions in the (tan β, mA ) plane are shown in Fig. 24 for the case

? > 0. The dependence of the tan β bounds on the sign of ? can be as large as ? tan β ? 30 for the mmax sceh nario, while in the case of the no-mixing scenario its e?ect is smaller, of the order of ? tan β ? 10 [21]. The cross sections are taken from [86] and are obtained from SM calculations and scaling factors σMSSM /σSM accounting for the modi?ed Higgs couplings. The D? search based on 1 fb?1 of data exploits the full mvis spectrum for the likelihood ratio limit calculation. Limits on tan β as a function of mA are derived for the mmax and no-mixing scenarios, where h only positive values of ? are considered. The result corresponding to the no-mixing scenario is represented in Fig. 25. A sensitivity of tan β ≈ 50 for mA below 180 GeV is obtained. The di?erence between the observed and expected limits are within two standard deviations or slightly above for mA > 250 GeV. It is mainly caused by a data excess in the ?τh channel for mvis > 160 GeV. The distributions of mvis in the three ?nal states are shown in Fig. 26. The combination of the LEP and Tevatron searches for neutral Higgs bosons is expected to probe vast regions of the (tan β,mA ) plane by the end of the Run II. In the no-mixing scenario shown in Fig. 24 and Fig. 25, the lower limits on tan β obtained at LEP [92] will slightly increase because of the assumed top mass mt = 174.3 GeV, which is higher than the currently measured value mt = 172.6 ± 1.4 GeV [16]. The Tevatron results are not sensitive to the precise value of the top mass. The upper limits will also extend with the growing data samples, together with the improvement of the CDF and D? searches. The projected sensitivity on the excluded domain would potentially allow exclu-

Arnaud Duperrin

Review - Page 18

Events

103

-1 D?, 1.0 fb ?τ h

102

Data Z→ττ Multijet W + jets

(a)

-1 D?, 1.0 fb eτh

Data Z→ττ Multijet W + jets

(b)

-1 D?, 1.0 fb e?

Data Z→ττ Multijet W + jets

(c)

Other EW + tt φ→ττ, 160 GeV
10

Other EW + tt φ→ττ, 160 GeV

Other EW + tt φ→ττ, 160 GeV

1

20 40 60 80 100120140160180200220240 40 60 80 100 120 140 160 180 200 220 240 60 80 100 120 140 160 180 200 220 240

Visible Mass (GeV)

Visible Mass (GeV)

Visible Mass (GeV)

Fig. 26. D? visible mass (mvis ) distributions used to search for neutral MSSM Higgs bosons decaying to tau pairs in the (a) ?τh , (b) eτh , and (c) e? channels with 1 fb?1 of data [91]. The signal φ→τ + τ ? corresponds to mφ = 160 GeV and is normalized to a cross section of 3 pb. The highest bin includes the over?ow.

Cross section (fb)

sion of tan β > 20 for values of mA up to few hundred GeV. 5.4 Charged Higgs bosons 5.4.1 t→bH + At the Tevatron, direct production of single charged Higgs bosons is expected to have negligible rate, and the direct production of H + H ? via the weak interaction is expected to have a relatively small cross section, on the order of 0.1 pb [73]. However, more significant production could be obtained in the decay of the top quark t→bH + , which would compete with the SM process t→bW + . The only recent search for t→bH + at Run II is from the CDF Collaboration, which has published a result based on 193 pb?1 of data [93]. The CDF search excludes the top quark branching fraction to a charged Higgs boson and b-quark BR(t→H + b) > 0.4 at 95% C.L. in the region 80 GeV < mH ± < 160 GeV, assuming BR(H + →τ + ντ ) = 1. Another search, interpreted in the context of the MSSM model, was for anomalous production of high transverse momentum tau leptons in the decay products of pairproduced top quarks using 335 pb?1 of data taken with the CDF detector in Run II [94]. An upper limit on BR(t→H + b) > 0.34 at 95% C.L. is set for a charged Higgs mass of 120 GeV.

102

D0, L = 1.1 fb-1 Theory(L) Theory(R) Observed Expected ±1 σ band
± CDF HR± excl. ± CDF HL ± excl.

10

80

Fig. 27. Cross section limit as a function of the doubly charged Higgs mass MH ±± at the 95% C.L. in the ?+ ?+ ?? ?? ?nal state using 1 fb?1 of data collected by the D? detector at Run II [101]. The mass regions excluded by CDF [98] and LEP [102] are also shown. The ±1σ uncertainty on the expected limit is represented by the band.

of data collected at Tevatron Run II. The search for p?→H ++ H ?? →?+ τ + ?? τ ? ?nal states has also been p performed by CDF [100] with 350 pb?1 . The D? Collaboration has recently submitted for publication a 5.4.2 Doubly charged Higgs bosons search for H ±± in the ?+ ?+ ?? ?? ?nal state using 1 fb?1 of data [101], and sets lower bounds for right±± ±± Doubly charged Higgs bosons H ±± are predicted in (HR ) and left-handed (HL ) bosons at 126 GeV and many scenarios, such as left-right symmetric models 150 GeV, respectively, at 95% C.L. This result is shown [95], Higgs triplet models and little Higgs models [96, in Fig. 27. In addition, CDF has published [103] with 97]. 292 pb?1 of data the case where the doubly charged Limits on doubly charged Higgs bosons have been Higgs boson lifetime is long (> 3 m), such that it depublished in the ee, e?, and ?? channels by the CDF [98] cays outside the detector. The lower mass bound on ±± ±± (D? [99]) experiment based on 240 pb?1 (113 pb?1 ) long-lived doubly charged HL and HR bosons are

LEP excl.

100 120 140 160 180 200 MH±± (GeV/c2)

Arnaud Duperrin

Review of Searches for Higgs Bosons and BSM Physics at the Tevatron - Page 19
Zγ : 0.026± 0.003 Wγ j: 0.046 ±0.005 QCD: 0.72± 0.15 DTP: 2.73± 0.55 Data: 5

Observed 3γ +X Events and Expected SM Background

Events/10 GeV/c2

1

10

D Run 2a Preliminary, 0.83 fb-1

1

B(h → γ γ )

10-1

10

-1

LEP D?, Run I Observed Expected Benchmark

10-2

f

10

-3

10-2

D?, 1.1 fb

-1

10-4 0

20

40

60

80

100

120

140

160

180

70

80

90

mi,j, GeV/c2

100 110 120 mhf (GeV)

130

140

150

Fig. 28. Distribution of two-body invariant mass for γγγ+ X events observed in 0.83 fb?1 of D? data along with the expected SM background [104]. The 2.73 ± 0.55 events are estimated from direct triphon production (DTP). This analysis is used to search for fermiophobic Higgs via the process p?→hf H ± →hf hf →γγγ(γ) + X. p

Fig. 29. Excluded branching fractions B(hf →γγ) as function of the fermiophobic Higgs boson mass mhf for the D? search with 1.1 fb?1 of data [62]. The signal is the sum of p?→V V →hf and p?→hf V processes. The theoretical p p curve uses the benchmark scenario assuming that the coupling hf V V (V = W, Z) has the same strength as in the SM and that all fermion branching fractions are exactly zero.

133 GeV and 109 GeV, respectively. When the two states are degenerate in mass, the limit is increased to mH ±± < 146 GeV at 95% C.L.

6 Extended Higgs models
In a more general framework, one may expect deviations from the SM predictions to result in signi?cant changes to the Higgs boson discovery signatures. One such example is the so-called “fermiophobic” Higgs boson [51,52,53], which has suppressed couplings to all fermions. Experimental searches for fermiophobic Higgs at LEP and Tevatron have yielded negative results so far. In fermiophobic models, the decay H ± →hf W ? can have a larger branching fraction than the conventional decays H ± →tb, τ ν. This would lead to double hf production. Searches have been conducted via the process p?→hf H ± →hf hf W ± →γγγ(γ) + X by the D? p experiment using 0.83 fb?1 of data [104]. Figure 28 shows the distribution of the diphoton invariant mass in data and from the expected backgrounds, where each event contributes three histogram entries since they are three possible photon-photon combinations. This analysis select 5 events in the data. The 2.73 ± 0.55 background events from direct triphon production (DTP), i.e., direct diphoton production (DDP) along with the FSR/ISR photon, are estimated by scaling the corrected number of diphoton events observed in data with the rate at which one would expect to observe a third photon in DDP processes from pythia. The background from events in which jets or electrons were misidenti?ed as photons is estimated in data and represents 0.8 ± 0.15 event. In absence of excess, a limit

is set at mhf > 80 GeV for mH ± < 100 GeV and tan β = 30 at 95% C.L. Another D? search for fermiophobic Higgs bosons has been recently submitted for publication using 1.1 fb?1 of data [62]. This analysis searches for inclusive production of diphoton ?nal states via Higgsstrahlung p?→hf V →γγ + X and vector boson fusion p?→V V p p →γγ+X processes (V = W, Z). The benchmark model used to set mass limits assumes that the coupling hf V V has the same strength as in the SM and that all fermion branching fractions are exactly zero. The study shown in Fig. 29 excludes fermiophobic Higgs bosons of mass up to 100 GeV at the 95% C.L. and represents the most stringent limits to date at a hadron collider. Technicolor models [105] provide an alternative dynamical explanation of electroweak symmetry breaking through a new strong gauge interaction acting on new fermions, called “techni-fermions”. The D? Collaboration published a search corresponding to 390 pb?1 of data [106] in the ?nal state containing one electron and two jets coming from the decay of vector techni-mesons (p?→ρT /ωT ) to a W boson and a p techni-pion πT , followed by the decays W →eν and πT →b? b?, or c?. As no signi?cant excess in the data b, c c was observed, limits have been set. For instance, a mass of mρT ≈ 210 GeV is excluded for the corresponding mπT ≈ 120 GeV at 95% C.L. Similarly, CDF presented a search for technicolor particles decaying into b? b? or bu and produced in association with W b, c bosons using 1.9 fb?1 of data [107]. Events matching the W + 2 jets signature are selected by requiring the electron or muon to be isolated with ET or pT > / 20 GeV, ET > 20 GeV, and at least one b-tagged jet. The number of tagged events and the invariant mass

Arnaud Duperrin
?±?0 σ(χ χ ) × BR(3l) (pb)

Review - Page 20

distributions of W + 2 jets and dijet events are consistent with the SM expectations. For mρT ≈ 250 GeV, the excluded mass range is 135 GeV < mπT < 145 GeV at 95% C.L.

0.5
-1 D? Run II Preliminary, 0.9-1.7 fb

0.4 0.3

~ 0 0 0 ± χ χ M(? )≈M(? )≈2M(? ); M(l)>M(? ) χ χ tanβ=3, ?>0, no slepton mixing Observed Limit Expected Limit
1 2 1 2

he q y-s av ua

7 Beyond the standard model
Beyond the elucidation of the mechanism of electroweak symmetry breaking, there are many compelling and well-motivated models that can be tested at the Tevatron. But what are the CDF and D? Collaborations looking for at Tevatron? By far, the most widely studied theory beyond the SM involves new particles predicted by low energy supersymmetry. Searches are therefore often divided into SUSY and non-SUSY categories. This succinct summary covers the following topics: ? Extension beyond the Poincar? group, i.e., supere symmetry, such as searches for electroweak gauginos with leptonic decay, and squark and gluino / production resulting in multijet+ET topologies. ? Existence of a new symmetry leading to massive particles with a lifetime comparable to the typical transit time through the detector. ? Particle substructure or compositeness, such that history repeats itself, leading to e.g., leptoquark particles or excited fermion states. ? An enlarged gauge group resulting in exotic Z ′ or W ′ bosons. ? An increase in the number of spacial dimensions, i.e., extra-dimension models with real Kaluza-Klein gravitons produced in association with a jet, or virtual Kaluza-Klein gravitons exchanged in the production of fermion or vector-boson pairs. ? A search for an excess in data without a speci?c model in mind. These are grouped into so-called signature-based searches.

rks

1

2

m 3lax

LEP
0.2 0.1

large-m 0 100 110 120

0

130

140

150

160

Chargino Mass (GeV)
Fig. 30. D? 95% C.L. limits on the total cross section for associated chargino and neutralino production with leptonic ?nal states as a function of the chargino (χ± ) mass, 1 in comparison with the expectation for several SUSY scenarios using 0.9-1.7 fb?1 of data [112]. The line corresponds to observed minimal SUGRA limit. PDF and renormalization/factorization scale uncertainties are shown as shaded bands. The lower mass limit at 103.5 GeV is from LEP searches [114].

8 Charginos and neutralinos
Charginos and neutralinos are respectively the charged and neutral partners of gauge and Higgs bosons. The primary search modes are pair production of charginos (χ+ χ? ) or associated chargino-neutralino (χ± χ0 ) pro1 1 1 2 duction, where χ± is the lightest chargino and χ0 is 2 1 the second lightest neutralino. A search for SUSY can therefore be performed via the associated production of charginos and neutralinos, where the χ± and χ0 are 2 1 assumed to decay either via exchange of vector bosons or via sleptons into SM fermions while the lightest neutralino remains undetected. The CDF and D? Collaborations have searched in the trilepton ?nal state. Published results are based on 320 pb?1 for D? [108] and 1.1 fb?1 for CDF [109,110, 111]. The eel channel was updated to 1.7 fb?1 by D? and, in combination with results in four other trilepton search channels based on approximately 1 fb?1 of data, new limits on the associated production of charginos and neutralinos have been set by the D? Collaboration

[112]. The CDF results were updated with 2 fb?1 of data [113]. The trilepton ?nal state has long been suggested to be one of the most promising channel for discovery of SUSY at a hadron collider. However, these searches suffer from a cross section below 0.5 pb with leptons that are di?cult to reconstruct due to their low transverse momenta, rendering the analyses challenging. Furthermore, many channels need to be combined to achieve sensitivity. The selection consists of two well identi?ed and isolated electrons (e) or muons (?) with a pT cut above ≈ 10 GeV. An additional isolated track provides sensitivity to the third lepton (l) and, by not requiring explicit lepton identi?cation, e?ciency is maximized. The presence of neutrinos and neutralinos in the ?nal state results in some missing transverse energy. Finally, since very few SM processes are capable of generating a pair of isolated like-charge leptons, the same analysis is performed with this looser criterion. The results are interpreted in minimal SUGRA inspired scenarios (mSUGRA) where gravity mediates SUSY breaking from the grand uni?cation theory (GUT) scale to the electroweak scale. With R-parity conservation (see section 11), mSUGRA can be completely characterized by ?ve parameters: a common scalar mass (m0 ), a common gaugino mass (m1/2 ), a common trilinear coupling value (A0 ), the ratio of the vacuum expectation values of the two Higgs doublets (tan β), and the sign of the Higgsino mass parameter (?). Direct searches at LEP set a lower limit on the mass of the chargino χ± at 103.5 GeV for sneutrino masses larger 1 than 200 GeV [114].

Arnaud Duperrin

Review of Searches for Higgs Bosons and BSM Physics at the Tevatron - Page 21

CDF Run II Preliminary, Ldt = 2.0 fb
NEvents / 2 GeV

0 ± ? ? σ(χ χ )×BR(3 leptons) (pb)



-1

± 0 Search for ? ? χχ 1 2

CDF Run II Preliminary

1.6 1.4 1.2 1 0.8 0.6

∫ Ldt = 2.0 fb

-1

± 0 Search for ?1? 2 χχ

104 10
3

Data Drell-Yan Dibosons tt

LEP direct limit

Theory σNLO×BR 95% CL Upper Limit: expected Expected Limit ± 1 σ Expected Limit ± 2 σ 95% CL Upper Limit: observed

102 10 1

2 1

mSUGRA m0=60, tan(β)=3, A0=0, (?)>0

10-1 10-2 10
-3

0.4 0.2
20 40 60 80 100 120 140 160 180 200 Missing E (GeV)
T

0

0

100

110

120

130

140 150 Chargino Mass (GeV/c2)

/ Fig. 31. ET distribution for di-lepton events with invariant mass 76 GeV < m?? < 106 GeV. This control region is used to test SM predictions of the CDF search for charginos and neutralinos using 2 fb?1 of data [113].

As a guideline, D? results are interpreted in this model with chargino χ± and neutralino (χ0 , χ0 ) masses 1 2 1 following the relation mχ± ? mχ0 ? 2mχ0 . The lep2 1 1 tonic branching fraction of chargino and neutralino depends on the relative contribution from the sleptonand W/Z-exchange graphs, which varies as a function of the slepton masses. Three mSUGRA inspired scenarios were used for the interpretation as shown in Fig. 30. Two of them are with enhanced leptonic branching fractions (“heavy squarks” and “3l-max” scenarios). For the 3l-max scenario, the slepton mass is just above the neutralino mass (mχ0 ), leading to maximum branch2 ing fraction into leptons. The heavy squark scenario is characterized by maximal production cross section. Finally, the large universal scalar mass parameter (m0 ) scenario is not yet sensitive because the W/Z exchange dominates. The new D? result [112] in the eel channel using 1.7 fb?1 of data observes no events after ?nal selection, with 1.0 ± 0.3 events expected from the SM background and between 0.5-0.2 events for the signal. In the dataset corresponding to 1 fb?1 , no candidates have been found in the e?? channel with an expected background of 0.9+0.4 events, while two candidates are ?0.1 found in the ??? channel consistent with the background expectation of 0.3+0.7 events. In the ee? chan?0.1 nel, no candidates have been found, with an expected background of 0.8 ± 0.7 events. The observation of one event in the data is consistent with the 1.1 ± 0.4 events expected from the background in the ?± ?± channel. Since no evidence for SUSY is reported, all results are combined to extract limits on the total cross section, taking into account systematic and statistical uncertainties including their correlations. The D? combination excludes chargino masses below 145 GeV at 95% C.L. for the 3l-max scenario. Similar analyses have been performed by CDF but interpreted with slightly di?erent scenarios and with

Fig. 32. CDF 95% C.L. limits on the total cross section for associated chargino and neutralino production with leptonic ?nal states using 2 fb?1 of data [113]. The expected limit corresponds to the dashed line, with ±1σ and ±2σ uncertainty bands shown. The next-to-leading order (NLO) production cross section corresponds to an mSUGRA model with the universal scalar mass parameter ?xed to m0 = 60 GeV.

a total integrated luminosity corresponding to 2 fb?1 of data [113]. After selecting dilepton events, a control region with 76 GeV < m?? < 106 GeV is used to establish a good understanding of the data and to test / the SM predictions. The ET distribution for this control region is displayed in Fig. 31. The low and high invariant mass regions are also explored. The search is splitted into ?ve exclusive channels and optimized for a benchmark signal point in the minimal SUGRA scenario, corresponding to m0 = 60 GeV, m1/2 = 190 GeV, tan β = 3, A0 = 0, and ? > 0. In this case, the masses mχ± = 119.6 GeV, mχ0 = 122 GeV, mχ0 = 67 GeV 1 2 1 have been computed with isajet [115] and the corresponding χ± χ0 production cross section 0.327 pb 1 2 with prospino-2 [116]. A total of 0.9±0.1 background events in the trilepton channels are expected for 4.5 ± 0.4 events from the signal, and 5.5 ± 1.1 background events for the dilepton+track channels for 6.9±0.6 signal events. CDF observes 1 event in the trilepton channel and 6 events in the dilepton+track channels. No excess is therefore observed and the resulting cross section limit shown in Fig. 32 is given as a function of the chargino mass for the benchmark mSUGRA scenario de?ned above but varying m1/2 . This scenario enhances the branching fraction of chargino and neutralino into leptons, and excludes chargino masses below 140 GeV for a sensitivity (expected limit) of 142 GeV at 95% C.L. Other models are being investigated for upcoming analyses with increased luminosity. The results between the two experiments cannot be directly compared since the ?xed low m0 value leads to a two-body decay for the CDF analysis, while for the D? analysis a sliding window of m0 is used to

Arnaud Duperrin

Review - Page 22

CDF Run II Preliminary

L=2.0 fb-1
observed limit 95% C.L. expected limit

Squark Mass (GeV)

600 500
D? II
D? IA

300
± LEP2 ? χ
? ? min[m( τ1),m(τ 2)] < m( χ1) ?0

Theoretical uncertainties included in the calculation of the limit

~± LEP2 l

250
A0=0, tanβ=5, ?<0

M1/2 (GeV/c )

UA1

UA2

CDF IB

300 200 100

no mSUGRA solution
D? IB

2

400

200

LEP m(l )



150

D?, L=2.1 fb-1 tanβ=3, A =0, ?<0
0
LEP

100
LEP m(χ1)


50
no mSUGRA solution

0 0

100 200 300 400 500 600

0 0

100

200

300

M0 (GeV/c )

2

400

500

600

Gluino Mass (GeV)
Fig. 33. D? Run II exclusion plane for squark and gluino masses at 95% C.L. using 2.1 fb?1 of Run II data [117], in the mSUGRA framework. The region excluded by previous results and this analysis is shown as the “D? II” shaded area. The thick (dotted) line is the limit of the observed (expected) excluded region for the nominal theoretical cross section. The band around these limits shows the e?ect of the PDF choice and of the variation of renormalisation/factorisation scale by a factor of two.

Fig. 34. Regions excluded by the squark and gluino analyses at the 95% C.L. in the (m0 , m1/2 ) plane, in the framework of mSUGRA assuming R-parity conservation, using 2 fb?1 of CDF Run II data [118]. The regions excluded by LEP chargino and slepton searches are shown. The nearly horizontal black lines are the iso-mass curves for gluinos corresponding to masses of 150, 300, 450 and 600 GeV. The other lines are iso-mass curves for squarks, corresponding to masses of 150, 300, 450 and 600 GeV.

keep the slepton mass slightly above the χ0 mass which 2 corresponds to a three-body decay.

9 Squarks and gluinos
9.1 Generic q and g searches ? ? In p? collisions, squarks (?) and gluinos (?), the superp q g partners of quarks and gluons, are expected ?rst to be abundantly produced if they are su?ciently light, and second to largely exceed the mass reach achieved at LEP. However, these searches have large background at the Tevatron. The ?nal states are studied within the framework of mSUGRA assuming R-parity conservation. All SUSY particles, except the lightest neutralino, are unstable and will therefore decay into their SM counterparts right after being produced, leading to a cascade decay with a ?nal state consisting of several jets from the squarks and the gluinos, plus missing transverse energy coming from the neutralinos. Note that to interpret the results of this search, the ten SUSY partners of the ?ve light quarks ?avors were considered to be degenerate in mass by D?. In the following, the squark mass is therefore de?ned as the average mass of all squarks other than the superpartners of the top. The CDF analysis assumes that only the ?rst and second generation masses are degenerated. The most constraining direct limits on squark and gluino masses are published by the D? Collaboration

[117], based on an analysis of 2.1 fb?1 of data. A preliminary result with similar sensitivity was shown by CDF [118] during the winter 2008 conferences with 2 fb?1 of data. Three di?erent scenarios have been probed by both CDF and D? experiments. The ?rst one corresponds to pair production of squarks, each decaying into a quark and a neutralino (?→qχ0 ), leading to a two q 1 / jets+ET ?nal state. This decay channel is dominant if the gluino is heavier than the squark (mq ? mg ). ? ? The second scenario applies when the squark is heavier than the gluino, leading to a ?nal state with 4 jets and / ET from g →?? q →q q χ0 . The third one addresses simi? q ? ? 1 lar squark and gluino masses, with a ?nal state of three or more jets arising from q g associated production. ?? Table 3 from D? illustrates the selection criteria used for these searches. The data show good agreement with SM expectations after requiring dedicated / / multijet+ET triggers and tight cuts on ET and the scalar pT sum (HT ). No signal is seen and cross section upper limits at 95% C.L. have been obtained for the sets of minimal SUGRA parameters considered (tan β = 5 (3), A0 = 0 (?2m0 ), ? < 0 for CDF (D?)). The two Collaborations show the results translated into the excluded regions in the (mg , mq ) and (m0 , m1/2 ) planes. ? ? The observed and expected mass limits derived for D? using 2.1 fb?1 are given in Fig. 33 as functions of the squark and gluino masses, improving on previous published limits. Lower limits at 95% C.L. of 379 GeV and 308 GeV on the squark and gluino masses, respectively, are derived in the most conservative hy-

Arnaud Duperrin

Review of Searches for Higgs Bosons and BSM Physics at the Tevatron - Page 23
Table 3. Selection criteria for the three squark and gluino analyses published by the D? Collaboration [117] with 2.1 fb?1 of data (all energies and momenta in GeV). |Vertex z pos.| is the longitudinal position of the interaction collision with respect to the detector center. The acoplanarity is de?ned as the azimuthal angle between the two leading jets. First and second (third and fourth) jets are also required to be central |η| < 0.8 (|η| < 2.5) with pT ≥ 35 GeV (pT ≥ 20 GeV for the fourth jet). The missing transverse en/ ergy and scalar pT sum are denoted ET and HT , respectively. The numbers of events observed and expected from SM backgrounds and from signal are given for each analysis (the ?rst uncertainty is statistical and the second is systematic).

Preselection Cut / ET |Vertex z pos.| Acoplanarity Selection Cut Trigger jet pT Electron veto Muon veto / ?φ(ET , jet1 ) / ?φ(ET , jet2 ) / ?φmin (ET , any jet) HT / ET Nbackgrd. Nsig. Nobs.

q q →qχ0 qχ0 ?? 1 1 dijet ≥ 35 yes yes ≥ 90? ≥ 50? ≥ 40? ≥ 325 ≥ 225 11.1 ± 1.2+2.9 ?2.3 10.4 ± 0.6+1.8 ?1.8 11

All Analyses ≥ 40 < 60 cm < 165? q g →qχ0 q q χ0 ?? 1 ? 1 multijet ≥ 35 yes yes ≥ 90? ≥ 50? ? ≥ 375 ≥ 175 10.7 ± 0.9+3.1 ?2.1 12.0 ± 0.7+2.5 ?2.3 9

gg →q q χ0 q q χ0 ?? ? 1 ? 1 multijet ≥ 35 yes yes ≥ 90? ≥ 50? ? ≥ 400 ≥ 100 17.7 ± 1.1+5.5 ?3.3 17.0 ± 1.2+3.3 ?2.9 20

pothesis by D?. The corresponding expected limits are 377 GeV and 312 GeV. For the particular case mq ? mg , squark and gluino masses below 390 GeV ? ? are excluded. The observed limit becomes 408 GeV for the NLO nominal signal cross section computed with the CTEQ6.1M PDF [119] and for the renormalization and factorization scale ?r,f = Q, where Q is taken to be equal to mg for g g production, mq for q q , and ?? ?? ? ? (mg + mq )/2 for q g production. The factor of two on ?? ? ? the renormalization and factorization scale reduces or increases the nominal signal cross sections by 15-20%. The PDF and ?r,f e?ects were added in quadrature to compute minimum and maximum signal cross sections. If one considers the less conservative scenario (maximum signal cross section), the observed lower mass limit for mq ? mg is 427 GeV at 95% C.L. ? ? The CDF search with 2 fb?1 excludes masses up to 392 GeV in the region where gluino and squark masses are similar, gluino masses up to 280 GeV for every squark mass, and gluino masses up to 423 GeV for squark masses below 378 GeV. Figure 34 shows the results of this analysis translated into the excluded regions in the mSUGRA (m0 , m1/2 ) plane. This search improves on the limit from indirect LEP searches for m0 values between 75 and 250 GeV and for m1/2 values between 130 and 170 GeV. However, the LEP Higgs search limits remain more constraining in a purely mSUGRA scenario [120]. The D? and CDF limits use slightly di?erent model parameters and methods to compute the excluded masses. Thus, they are not directly comparable. However, it was veri?ed that similar results hold for a large class of parameter sets. A complementary search for squarks has been performed by D? in the topology of multijet events accompanied by large missing transverse energy and at least one tau lepton decaying hadronically using 1 fb?1 of data [121]. Lower limits on the squark mass up to

mχ0 (GeV) ?

100 80 60 40 20 0 40

CDF Run II 295 pb-1 D0 Run II 360 pb Observed Expected
-1
o

m

~t

=

m ?χ 1

+

mc

-1 D?, L = 995 pb

1

LEP θ = 56o LEP θ = 0o

+ m
~t

mb

+

m ?χ

o

=

MW

60

80

100

120

140

m~t (GeV)
Fig. 35. D? 95% C.L. exclusion contours in the stop and neutralino mass plane, assuming a stop branching ratio of 100% into a charm quark and a neutralino. This search is based on 1 fb?1 of data [122].

366 GeV are derived in the framework of mSUGRA with parameters enhancing ?nal states with taus. This analysis has the advantage of providing additional sensitivity for squark searches, mainly at large values of tan β.

9.2 Stop and sbottom searches For the third generation, mass uni?cation is broken in many SUSY models due to potentially large mixing effects. This can result in a sbottom or stop with much

Arnaud Duperrin

Review - Page 24

CDF Run II Preliminary

Sbottom Mass (GeV/c2 )

∫ L dt=1.8 fb

-1

120 110

Kinematically excluded LEP I LEP II ALO D0 Run II (e?,??) obs 428 pb D0 Run II (e?,??) exp 428 pb D0 Run II (e?) obs 1fb-1 D0 Run II (e?) exp 1fb-1
-1 -1

D0 RunII Preliminary L=1 fb
-1

350

Observed 95% CL limit
2 M(? ) = 60 GeV/c χ ~) = 500 GeV/c 2 M(q

fo r

300
m at ic

bi

dd

100
Mν (GeV/c2 ) ?

en

al

90 80 70 60 50 40 60 80 100 120 140 M ~ (GeV/c2) t
1

200
Run II 156 pb Excluded Limit
-1

g~→

bb ~ 1 k i

250

ne

ly

150

D? Run II 310 pb Sbottom Pair Production Excluded Limit

-1

CDF Run I excluded

160

180

200

100

200

250

300

350

400

Gluino Mass (GeV/c2)
Fig. 36. CDF 95% C.L. exclusion contours in the sbottom and neutralino mass plane, assuming gluino pair production where the gluino decays to b? with subsequent sbottom b decay to a b-quark and the lightest neutralino. This search is based on 1.8 fb?1 of data [127].

Fig. 37. D? 95% C.L. exclusion contours in the stop and ? sneutrino mass plane, assuming t→b?? and ν →νχ0 decay ν ? 1 modes using 1 fb?1 of data [130].

lower mass than the other squarks and gluinos. In addition, the lightest stop quark could well be the lightest of all quarks because of the impact of the large top Yukawa coupling on the renormalization group equations. Dedicated searches are conducted in a general MSSM ? framework assuming the decays t → cχ0 and ? → ?1 b 0 bχ1 are the only ones kinematically allowed. Despite a ? ? much smaller cross section for t and ? production comb pared to previous generic squark searches, heavy-?avor tagging can be used to reduce the important SM backgrounds. However, in the mass range of interest, the jets are much softer compared to the generic squark search, and therefore the QCD multijet background is much larger, reducing the stop and sbottom masses which can be excluded. D? has recently submitted for publication an update using 1 fb?1 of data [122] compared to previous D? [123] and CDF [124] published results with about 300 pb?1 of the case where the stop decays with a branching ratio of 100% into a charm quark and a neutralino. Good agreement between the data and the SM prediction is obtained. The derived limits at 95% C.L. on the stop mass are shown in Fig. 35. With the ? theoretical uncertainty on the t pair production cross section taken into account, the largest limit on mt is ? 150 GeV, for mχ0 = 65 GeV. 1 At large values of tan β, the mixing can be enhanced in the sbottom sector. The analysis of the decay channel ? → bχ0 is similar to the one applied for b ?1

the stop except that higher masses can be excluded because heavy-?avor tagging is more e?cient for b-jets than for c-jets. Supersymmetric bottom quark masses up to 193 GeV for a neutralino mass of 40 GeV are excluded by CDF with 295 pb?1 of data [124]. For the D? analysis [125] using 310 pb?1 , the maximum m? excluded is 222 GeV, which is the most restrictive b limit on the sbottom mass to date from direct ? pair b production. The CDF Collaboration also considered the scenario where the sbottom could be produced through the decay of gluinos into bottom and sbottom quarks, yielding a signature consisting of four b-jets and two neutralinos from the sbottom decay ? → bχ0 . Requirb ?1 ing inclusive double b-tagging, CDF observes 4 events where 2.6 ± 0.7 are expected in 156 pb?1 of Run II data [126]. Exclusion lower limits have been published on the masses of the gluino and sbottom up to 280 and 240 GeV, respectively. This result has been recently updated with 1.8 fb?1 of CDF data [127]. At least one b-tagged jet was required and two di?erent signal regions were optimized. In the small (large) ?m = mg ? mχ0 region, 19 (25) events are observed ? ?1 for 22.0 ± 3.6 (22.7 ± 4.6) events expected from SM processes. The (m?,mg ) exclusion contour plot at 95% ? b C.L. is shown in Fig. 36. A lower gluino mass limit mg > 340 GeV is set for m? = 300 GeV, mχ0 = ? ?1 b 60 GeV, and mq = 500 GeV. ? The D? Collaboration has searched for a light stop in the lepton+jets channel using two scenarios. The ? ?rst one uses the stop decay modes t1 →tχ0 → bW + χ0 . 1 1 In this analysis, kinematic di?erences between stop ? pair production and the dominant tt process are used to separate the two possible contributions. The preliminary results [128] with 1 fb?1 set upper cross section

Arnaud Duperrin

Review of Searches for Higgs Bosons and BSM Physics at the Tevatron - Page 25 set a stau lower limit. In anomaly mediated supersymmetry breaking (AMSB), or in models that do not have gaugino mass uni?cation, the signature is the same for long-lived charginos that escape the detector [133]. The larger production cross section allows a preliminary lower limit of 140 GeV on higgsino-like charginos and 174 GeV on gaugino-like charginos, both at the 95% C.L. 10.2 Diphoton ?nal state

Events per 3 GeV

10

3

D? 1.1 fb

-1

102 10 1 10
-1

data γγ W/Z+γ γ electron mis-ID jet mis-ID SM + signal Λ=75 TeV SM + signal Λ=90 TeV

0

20 40 60 80 100 120 140 160 180 200

Missing E (GeV)
T

/ Fig. 38. D? ET distribution in 1.1 fb?1 of γγ data, along with expected background processes [139]. The expected / ET distribution for GMSB SUSY signal with Λ = 75 TeV and 90 TeV are presented as dotted and dashed lines, respectively.

?? limits at 95% C.L. on t1 t1 production that are a factor of about 7-12 higher than expected for the MSSM model for stop masses ranging between 145-175 GeV. The second scenario considers the pair production of the stop decaying into a b-quark and the supersymmetric partner of the neutrino,i.e., the sneutrino (?). ν ? This decay t→b?? is then followed by the ν →νχ0 inν ? 1 volving only invisible particles. The ensuing ?nal state consists of two leptons, two b-jets and missing transverse energy. The result combines e?+jets and ??+jets ?nal states and limits are set in the plane (mt? , mν ) ? 1 as shown in Fig. 37. The published result [129] with 428 pb?1 of data has been recently updated [130] with 1.1 fb?1 and there is now good agreement between the expected and observed limits.

10 Gauge mediated SUSY breaking
In gauge mediated SUSY breaking models (GMSB), the gravitino, with a mass less than few keV, is the LSP. The phenomenology of these models is therefore determined by the nature and the lifetime of the nextto-lightest supersymmetric particle (NLSP), which can be either a neutralino or the lightest stau, depending on the choice of model parameters [3].

/ Final states with two photons and ET can be produced in GMSB models. In such a scenario, the lightest neutralino (χ0 ) decays into a photon and a weakly in1 ? teracting stable gravitino (G). Most of the searches ? assume the prompt decay χ0 → γ G. The CDF Col1 laboration, however, also searched in 570 pb?1 of data for non-prompt decays and a χ0 with a lifetime that is 1 on the order of nanoseconds or more [134]. Two candidate events, consistent with the background estimate of 1.3±0.7 events, are selected based on the arrival time of the photon at the calorimeter. This result allows for setting both quasi-model-independent cross section limits and for an exclusion region of GMSB models in the χ0 lifetime versus mass plane (τχ0 ,mχ0 ), with 1 1 1 a mass reach of 101 GeV for τχ0 = 5 ns. 1 ? As for the prompt decay χ0 → γ G, CDF [135] and 1 D? [136] combined their published results based on 200-260 pb?1 of data. The combined limit [137] excludes a chargino mass of less than 209 GeV, for GMSB parameters following the “Snowmass benchmark scenario” [138]: messenger mass mM = 2Λ where Λ is the e?ective SUSY-breaking scale, tan β = 15, ? > 0, and the number of messenger ?elds NM = 1. The D? Collaboration recently published an update us/ ing 1.1 fb?1 of data [139]. The ET distribution for the γγ sample is given in Fig. 38 with the expected signal contribution for two di?erent values of the e?ective energy scale Λ. After determination of all backgrounds from data, D? observes no excess of such events and thus sets 95% C.L. limits: the masses of the lightest chargino and neutralino are found to be larger than 229 GeV and 125 GeV, respectively. These results represent the most stringent limits to date on this particular GMSB SUSY model.

11 R-parity violation
The MSSM superpotential is minimal in the sense that it is su?cient to produce a phenomenologically viable model. However, the most general gauge-invariant and renormalizable superpotential would include additional terms like ? ? ? ? ? WRPV = λijk Li Lj Ek + λijk Li Qj Dk + λijk Ui Dj Dk , where i = 1, 2, 3 are the family indices. The lepton and quark doublet super?elds (weak isospin singlet super?elds) are denoted L and Q (E, U and D), respectively.
′ ′′

10.1 Long-lived ?nal state It is possible for a stau NLSP in these models to be longlived [131]. Stau pair production has been searched for by D? using 390 pb?1 of data [132]. These long-lived particles loose energy principally by ionization and can traverse the entire detector, registering in the muon detectors. The search is not yet sensitive enough to

Arnaud Duperrin
CDF Run II Preliminary (1.0 fb-1)

Review - Page 26

D?, 1.04 fb-1
Events/10 GeV
10

Events / 10 GeV

data Z/γ * → ττ di-boson tt signal

102

Central ?, p > 40 GeV
T

Background Prediction 220 GeV/c2 Stop

10

1

1

10-1
10-1 0 50 100

Me?(GeV)

150

200

250

300

0

50 100 150 200 Mass from track momentum and β

TOF

250 (GeV/c2)

300

Fig. 39. Invariant mass of the electron-muon system in 1 fb?1 of data collected by the D? experiment [144]. The search is performed in the context of R-parity-violating production and decay. The dashed line indicates the signal hypothesis for a third-generation sneutrino (?τ ) with a ν mass of 100 GeV and σ × Br of 0.057 pb.

Fig. 40. Mass distribution measured in 1 fb?1 of data by the time-?ight ?ight and transverse momentum of tracks in events collected by the CDF experiment using the high transverse momentum muon trigger. The expected contribution from stable stop pair production is shown for a stop mass of 220 GeV [153].

These terms violate both baryon number (B) and lepton number (L), which is in contradiction with experimental observations. The most obvious experimental constraint comes from the non-observation of proton decay, which would violate both B and L by 1 unit. Therefore, these new couplings in the trilinear terms, if present in nature, must be extremely small. In the MSSM, a new symmetry is thus introduced to eliminate the possibility of B and L violating terms in the superpotential. This new symmetry, called R-parity [3], is a multiplicatively conserved quantum number de?ned as P = (?1)3(B?L) , which takes a value of +1 for SM particles and -1 for SUSY particles. The CDF and D? Collaborations have considered a number of scenarios under the hypothesis that Rparity violation (RPV) can occur. The experimental consequences are characterized by less missing transverse energy and more leptons and jets in the ?nal states, due to the decay of the LSP into SM particles. In addition, sparticles may be resonantly produced by RPV couplings as single sparticles, by virtue of which the LSP cannot be a candidate for dark matter. Searches for gaugino pair production via λ121 and λ122 with a signature of at least four charged leptons and two neutrinos are published by CDF [140] (D? [141]) using 346 pb?1 (360 pb?1 ) of data. The case in which a τ appears in the ?nal state via λ133 coupling has been included in the D? analysis. Using the mSUGRA model with m0 = 1 TeV, tan β = 5, and ? > 0, D? obtains 95% C.L. lower limits on the χ0 1 (χ± ) masses of 119, 118, 86 GeV (231, 229, 166 GeV) 1 for the corresponding λ121 , λ122 , and λ133 couplings, respectively. For the CDF analysis, the χ0 mass limits 1 range from 98 to 110 GeV, while the chargino mass limits range from 185 to 203 GeV at 95% C.L., depending on the choice of model parameters.

A search for pair production of scalar top quarks ′ decaying via the R-parity-violating λ333 coupling to a τ lepton and a b quark has been presented by the CDF Collaboration based on 322 pb?1 of data [142]. A lower mass limit mt1 > 151 GeV has been set in the ? ?nal state of either an electron or a muon from the ?rst τ decay, a hadronic decay for the second τ , and two or more jets. Resonant slepton production has also been probed at the Tevatron. A single slepton could be produced in hadron collisions by LQD interactions followed by decays into SM di-lepton ?nal states via LLE interactions, leading to a high-mass di-lepton resonance. The CDF [143] and D? [144] Collaborations have reported a search for resonant production of sneutrinos decaying into an electron and a muon using 344 pb?1 and 1 fb?1 of data, respectively. The invariant mass of the electron-muon system in the D? search is shown in Fig. 39. For a sneutrino with mass of 100 GeV, ′ λ311 > 1.6×10?3 is excluded by D? at 95% C.L. when the λ312 coupling constant is ?xed at 0.01. CDF ex′ cludes λ311 values above 0.01 for a ντ mass of 300 GeV ? and λ132 > 0.02. In addition, CDF published sneutrino ′ mass limits depending on the λ and λ couplings considered in the other ee, ??, τ τ ?nal states based on ≈ 200 pb?1 [145,146]. Results from D? have been published [147] based on 380 pb?1 on the production and decay of resonant smuons and muon-sneutrinos in the channels ? → ? χ0 ?, ? → χ0 ?, and ν? → χ± ?. A lower limit on ?1 ? ?2,3,4 ? ?1,2 ′ the slepton mass m? ≤ 363 GeV is set for λ211 ≥ 0.10, l tan β = 5, A0 = 0 and ? < 0.

Arnaud Duperrin

Review of Searches for Higgs Bosons and BSM Physics at the Tevatron - Page 27
q q g q LQ2 LQ2 l q g l LQ2 l q LQ2 λ q

12 Long-lived particles
Although cosmological considerations put strict limits on new particles that are absolutely stable, these restrictions do not apply to particles that live long enough to decay outside the detector [148]. Several models, outlined below, predict charged or neutral longlived particles decaying inside or outside the detector. 12.1 Neutral long-lived particles The existence of neutral long-lived particles decaying into two leptons that arise from a highly displaced vertex is expected in “hidden valley” theories [149] or SUSY models with R-parity violation [3]. Motivated by the excess of di-muon events observed by the Fermilab neutrino experiment NuTeV [150], D? has published [151] a search based on 380 pb?1 of data assuming a benchmark model where the χ0 has traveled 1 at least 5 cm and decays via RPV to ?+ ?? ν. The background has been estimated to be about one event and, since no candidates were observed, a 95% C.L. upper cross section limit of 0.14 pb is set on pair-production of neutral long-lived particles with a mass of 10 GeV and a lifetime of 4 × 10?11 .

l

Fig. 41. Examples of leading-order Feynman graphs for pair-production (left) and single production (right) of leptoquarks.

of a gluino and other quarks or gluons could be pair produced through strong interactions. As studied in Ref. [158], some charged R-hadrons have the potential to become “stopped gluinos”, by losing all of their momentum through ionization and come to rest in the calorimeter. No excess is observed above the primary source of background coming from cosmic muons in 410 pb?1 of D? data [159]. Their main decay mode is expected to be g →gχ0 with a lifetime assumed to ? 1 be long enough such that the decay of the gluino occurs during a bunch-crossing adequately later than the one which has produced it (about 30 ?s). Limits are therefore placed on the gluino cross section times the stopping probability as a function of the gluino and χ0 1 12.2 Charged long-lived particles masses, for gluino lifetimes from 30 ?s to 100 hours. This analysis excludes mg < 270 GeV for a χ0 mass ? 1 If a long-lived particle has a large mass and is charged of 50 GeV, assuming a 100% branching fraction for (CHAMP) [152], it will appear in the detector as a g →gχ0 , a gluino lifetime less than 3 hours, and a neu? 1 slowly moving, highly ionizing particle with large transtral to charged R-hadron conversion cross section of verse momentum that can be observed in the muon 3 mb. detectors. CDF has performed a model independent search by measuring the time-of-?ight of particles from muon triggers in 1 fb?1 of data [153]. As shown in Fig. 40, the result is consistent with muon background 13 Leptoquarks expectation. Within the context of stable stop pair Leptoquarks (LQ) are colored bosons that were posproduction, CDF infers an upper mass limit of 250 GeV tulated to explain the parallels between the families of at 95% C.L. ′ quarks and leptons [160]. They are predicted in many The introduction of a fourth generation quark b extensions of the standard model, such as SU(5) grand provides another possibility for such long-lived paruni?cation [161], superstring [162], and compositeness ticles [154]. The CDF Collaboration reported [155] a models [163]. Figure 41 shows mechanisms for lepto?1 result, based on 193 pb of data, for such particles quark production and decay in p? collisions, where lepp using Z boson decays to muons and reconstructing ditoquarks can be pair produced via the strong interac′ muon vertices in the tracker. D? also performed a b tion. Single leptoquark production can also occur in search, using the capability of its detector to recon- association with a lepton. struct the direction of electromagnetic showers, and thus enhancing its sensitivity to long-lived particles. Although limits have been set within the framework of 13.1 LQ pair production ′ the b model, loose requirements are imposed to limit potentially model-dependent selection. No evidence of At the Tevatron, LQ states would be predominately such excess is found in 1 fb?1 of data by D? [156]. pair produced with larger cross sections predicted for Limits are set on the production cross section and life- vector (spin 1) than for scalar (spin 0) leptoquarks. time of such long-lived particles that decay into a Z They are expected to decay into a quark and a charged boson or any ?nal state with a pair of electrons or lepton with a branching fraction β, or into a quark and photons with mass above 75 GeV at 95% C.L. a neutrino with a branching fraction (1 ? β). ExperIn a variant of SUSY known as split supersymme- imental limits on lepton number violation, on ?avortry [157], gluino decays into squarks and the neutralino changing neutral currents, and on proton decay motiLSP are suppressed, leading to a long lived gluino. At vate the assumption that there would be three di?erthe Tevatron, such colorless bound states (R-hadrons) ent generations of leptoquarks, where each leptoquark

Arnaud Duperrin generation couples to only one generation of quarks and leptons. Results have been published by CDF for ?rst generation scalar leptoquarks (LQ1 ) using about 200 pb?1 of data. No evidence is observed of such particles in the topologies arising from LQ1 LQ1 → eqeq, LQ1 LQ1 → eqνq, and LQ1 LQ1 → qνqν [164,165]. Lower mass limits are derived: 236, 205 and 145 GeV for β = 1, β = 0.5 and β = 0.1, respectively. The LQ1 mass limits which are published in the eqeq and eqνq ?nal states by D? with 252 pb?1 of data are 256 and 234 GeV, for β = 1 and 0.5, respectively [166]. In LQ1 LQ1 →qνqν, D? has published [167] a result with 310 pb?1 and a lower mass limit of 136 GeV is set at the 95% C.L. Recently, CDF has released a search / based on 2 fb?1 of dijet+ET data [168]. Two separate analyses are performed. The ?rst one requires two jets with pT > 30 GeV, no third jet with pT > 15 GeV, / ET > 80 GeV, and HT > 125 GeV. The second one search in the high kinematic region de?ned by HT > / 225 GeV and ET > 100 GeV. In both regions, CDF compares the expected SM backgrounds with data and no excess is observed. A scalar leptoquark model is used to place a limit of mLQ1 > 177 GeV, for β = 0 at 95% C.L. Second generation scalar leptoquarks (LQ2 ) have also been searched for at the Tevatron. The CDF Collaboration has published a result in the dimuons+jets and muon+missing energy+jets topologies using 198 pb?1 of data [169]. Combining the results with those / from the ET +jets channel topology [165], CDF excludes LQ2 with masses below 226 GeV for β = 1, 208 GeV for β = 0.5, and 143 GeV for β = 0.1 at 95% C.L. The D? Collaboration has published limits in the channel LQ2 LQ2 → ?q?q using an integrated luminosity of 294 pb?1 [170]. In combination with previous D? measurements, lower mass limits of mLQ2 > 251 GeV for β = 1 and mLQ2 > 204 GeV for β = 0.5 are set. The ?rst D? search performed in Run II in the channel LQ2 LQ2 →?qνq, which has maximal sensitivity for β = 0.5, is based on 1 fb?1 of data [171]. From this analysis alone, a lower mass limit for scalar second generation leptoquarks of mLQ2 > 214 GeV at β = 0.5 is / set at 95% C.L. Using 2 fb?1 of dijet+ET data, CDF excludes LQ2 masses below 177 GeV at 95% C.L [168]. A search for third generation scalar LQ3 pair production has been performed in the τ bτ b channel using 1 fb?1 of data collected at D? [172]. To increase the search sensitivity, advantage is taken of the presence of heavy-?avor jets in the signal. No evidence of signal has been observed, and limits are set on the production cross section as a function of the leptoquark mass. Assuming β, the branching fraction of the leptoquark into τ b, equal to 1, the limit on the mass is 180 GeV at 95% C.L. With a smaller dataset of 0.4 fb?1 , assuming a decay into bν, the limit is 229 GeV [173]. If leptoquark decays into a τ lepton and a top quark are taken into account, and if equal couplings are assumed, a mass limit of mLQ3 > 221 GeV is set by D? at 95% C.L. [173]. The CDF Collaboration has performed a similar analysis with 322 pb?1 of data

Review - Page 28

|<1) (pb)

103

CDF Run II Preliminary, 1.13 fb
95% CL limits (for R-S G, Technirho) 95% CL limits (for the others) Technirho

-1

σ × Br × Acceptance (|y

jet1,2

102

R-S G (k/Mpl=0.1)

10

Excited quark Axigluon/Coloron

1

E6 diquark

10-1

10-2

400

600

800

1000

1200 1400 2 Mass [GeV/c ]

Fig. 42. CDF 95% C.L. limits based on 1.1 fb?1 of data [183] on the Randall-Sundrum graviton (G→q q , gg [184]), color-octet techni-rho production ? (ρT →q q , gg [185]), excited quark (q ? →qg [181]), ax? igluon and ?avor-universal coloron (A→q q [186]), and ? E6 di-quark (D(Dc )→(qq)?q [162]), compared with the q? theoretical predictions for production of these particles.

but in the context of vector leptoquarks (V LQ3 ). Assuming Yang-Mills (minimal) couplings, CDF obtaines the most stringent upper limit on the V LQ3 pair production cross section of 344 fb (493 fb) and lower limit on the V LQ3 mass of 317 GeV (251 GeV) at 95% C.L in τ b decay [174]. Finally, a mass limit of mLQ3 > 167 GeV is set for third generation of scalar / leptoquark using 2 fb?1 of CDF dijet+ET data [168]. In this case, the e?ciency for third generation events to pass a dijet plus missing ET selection criteria is smaller due to lepton rejection requirements, and therefore the mass limits set are lower than those for the ?rst and second generation. 13.2 Single LQ production The production of single leptoquarks leads to ?nal states consisting of two leptons and one jet. The D? Collaboration has published a search in the ??j ?nal state using 300 pb?1 of data [175]. Compared to the search for leptoquarks which considered only pairproduction, the mass limits are improved to mLQ > 274 GeV for β = 1 and λ = 1, where λ is the leptoquarklepton-quark coupling. For β = 0.5, a lower limit on the mass of a second generation scalar leptoquark mLQ > 226 GeV is set at 95% C.L.

14 Compositeness
In the SM, the quarks and leptons are treated as fundamental particles. However, one proposed explanation

Arnaud Duperrin

Review of Searches for Higgs Bosons and BSM Physics at the Tevatron - Page 29

Events/(10 GeV/c )

for the three generations is a compositeness model of the known leptons and quarks [176]. 14.1 Excited lepton Compositeness models comprise a large spectrum of excited states. The CDF and D? Collaborations have searched for excited electron (e? ) in the process p?→e? e, with the e? subsequently decaying to an elecp tron plus photon. The agreement observed by D? in 1 fb?1 [177] and CDF in 202 pb?1 [178] of data with the SM backgrounds are interpreted in the context of a model that describes production by four-fermion contact interactions (CI) and excited electron decay via electroweak processes. Choosing the scale for CI to be Λ = 1 TeV, e? masses below 756 GeV are excluded at 95% C.L. by the D? analysis. To make a comparison with LEP results, CDF also reinterprets its search in the gauge-mediated model and excludes 126 GeV < me? < 430 GeV at 95% C.L. for the phenomenological coupling f /Λ ≈ 10?2 GeV [178]. Similarly, searches for excited muons (?? ) subsequently decaying to a muon plus photon have been carried out in a data sample corresponding to an integrated luminosity of 371 pb?1 for CDF [179] and 380 pb?1 for D? [180]. CDF excludes in the contact interaction model 107 GeV < m?? < 853 GeV for Λ = m?? and in the gauge-mediated model 100 GeV < m?? < 410 GeV for f /Λ ≈ 10?2 GeV at 95% C.L. Choosing the scale for contact interactions to be Λ = 1 TeV, masses below 618 GeV are excluded by the D? search. 14.2 Excited quark The D? Collaboration has published a search within the framework of a quark substructure model [181]. In 370 pb?1 of data, no indication for resonances in the Z+jet channel has been observed, where the Z boson is detected via its Z→e+ e? decay mode. This analysis leads to a mass limit mq? > 510 GeV at 95% C.L., assuming the decay mode q ? →q + Z for the excited quark [182]. The CDF preliminary result based on 1.1 fb?1 of data excludes the mass region 260 GeV < mq? < 870 GeV at 95% C.L. assuming the decay mode q ? →qg [183]. The obtained limits are shown in Fig. 42 for various models corresponding to the production of new particles that decay into dijet. In the same vein, CDF searched for new particles that lead to a Z boson plus jets but, this time, in the context of a fourth generation model [154]. In a data sample of 1 fb?1 , the Z boson decays to ee and ′ ?? are used to set a lower limit on b quark masses below 268 GeV at 95% C.L., assuming the decay mode ′ b →b + Z [187]. In 1.9 fb?1 of lepton+jet data, CDF also investigated the existence of a massive gluon and set limits on the coupling strength of this particle as function of ′ its mass [188]. A search for the heavy top (t ) quark pair production decaying to W q ?nal states in 2.3 fb?1

CDF Run II Preliminary
2

140 120 100 80 60 40 20 160 180 200 220 240

Events/(10 GeV/c )

105 104 103 10
2

L = 2.5 fb-1 data Drell-Yan QCD Other SM
260 280 300 320 340 2 M(ee) (GeV/c )

2

10 1

10-1 10-2 10-3 10-4 100 200 300 400 500 600 700 800 900 1000
2

M(ee) (GeV/c )
Fig. 43. The dielectron mass measured by CDF and the expected background in 2.5 fb?1 of data [192]. A slight excess in the data is observed in the region me+ e? ≈ 240 GeV.

of CDF lepton+jets data excludes a fourth-generation ′ t quark with a mass below 284 GeV at 95% C.L [189].

15 Extra gauge bosons
Multiple extensions of the SM predict extra gauge bosons. ′ For instance, Z are predicted in E6 GUTs models [190], ′ and W bosons appear in models such as left-rightsymmetric theories [191]. The new gauge group can comprise a new mixing angle and new couplings depending on the models considered.


15.1 Z bosons The CDF Collaboration has recently released a new preliminary result in the search for dielectron resonances using 2.5 fb?1 of data [192]. The previous CDF searches have been published with 0.2-1.3 fb?1 of data [145,193,194]. Resonance with dilepton in the ?nal states have always been leading channels for early discovery searches due to low backgrounds. In addition, lepton energy and momentum can be measured precisely by combining calorimeter and tracking information. The searches are performed by reconstructing the dielectron mass, as shown in Fig. 43. The Z mass peak and the Drell-Yan tail at high mass is well reproduced by the SM background prediction. However, in the region me+ e? ≈ 240 GeV, an excess of data over background of 3.8σ is observed, with a 0.6% probability that it is caused by the background ?uctuation, given that the search probes the mass range 150 GeV-1 TeV. A typical di-electron event is displayed in Fig. 44.

Arnaud Duperrin By performing a scan for high-mass resonances, CDF sets limits depending on the model considered. For instance, a lower mass limit of 966 GeV can be ′ set assuming SM-like couplings of the Z , with a some′ what lower mass limit for E6 Z bosons with masses below 737/933 GeV (lightest/heaviest) GeV excluded at 95% C.L. The D? Collaboration has presented a preliminary results [195] with 200 pb?1 of data and ′ excludes lower masses for Z boson with SM-like couplings to fermions of 780 GeV at 95% C.L. The e+ e? ?nal state can also easily be reinterpreted in the context of technicolor models, which predict large amounts of techniparticle production at the Tevatron [196]. Degenerated technihadrons (ρT , ωT ) decaying into e+ e? are excluded for certain model parameters with masses below 367 GeV, based on 200 pb?1 of D? data [197]. Similar analyses in the dimuon channel have been carried out by CDF based on 200 pb?1 of data [145] and by D? with 250 pb?1 of data [198]. The signal ′ process Z →τ + τ ? has been searched by CDF with ?1 195 pb of data and a lower mass limit of 399 GeV (SM couplings) has been set [146]. A general search for resonances decaying to a neutral e? ?nal state based on 344 pb?1 of CDF data has been interpreted in the context of lepton family ′ number violating (LFV) Ql couplings [199] of the Z 12 ′ boson and E6 -like models of U (1) symmetry [200]. A search for a narrow-width heavy resonances de? caying into top quark pairs X→tt based on 913 pb?1 has been submitted for publication by D? [201]. This result was recently updated with 2.1 fb?1 of data for the winter 2008 conferences [202]. Within a topcolorassisted technicolor model [203], the existence of a lep′ tophobic Z boson with mass mZ ′ < 760 GeV and width ΓZ ′ = 0.012mZ ′ are excluded at 95% C.L. Sim? ilarly, CDF performed several searches for a tt resonance in the lepton+jets ?nal state using 680 pb?1 [204] ′ and 1 fb?1 [205] of data. A leptophobic Z predicted by the topcolor theory is excluded below 725 GeV. 15.2 W bosons Both CDF [206] and D? [207] have published results ′ of searches for a heavy charged vector boson (W ) decaying to an electron-neutrino pair using 205 pb?1 and 1 pb?1 of data, respectively. In the context of a ′ W with SM coupling to fermions, and for these data samples, the lower mass limits are 1 TeV for D? and 788 GeV for CDF, at 95% C.L. In a similar analysis that exploits 1.1 fb?1 of dijet data, CDF excludes ′ at 95% C.L. the existence of W in the mass range 280 < mW ′ < 840 GeV [183]. ′ W bosons that couple to right-handed fermions may not be able to decay to leptonic ?nal states if the corresponding right-handed neutrinos (νR ) are too massive. In this case, only hadronic decays are possi′ ble. To investigate the possibility of W decaying into t? D? and CDF have used a similar approach as for b,


Review - Page 30

Et = 125.00 GeV

Fig. 44. Event display of a typical dielectron event, as measured by CDF in Run II [192].

their single top searches. The D? Collaboration has published a result using 230 pb?1 of data which ex′ cludes masses between 200 GeV and 610 GeV for a W boson SM couplings [208]. This search has been updated with approximately 0.9 fb?1 of data [209]. For a left′ handed W boson with SM couplings, D? sets a lower ′ mass limit of 731 GeV. For right-handed W bosons, the lower mass limits on this hypothetical new particle ′ at 95% C.L. are 739 GeV assuming that the W boson decays to both leptons and quarks, and 768 GeV if it decays only to quarks. Assuming SM couplings to ′ fermions for the W , CDF has used 1.9 fb?1 of data to set limits of mW ′ < 800 GeV when mW ′ > mνR and mW ′ < 825 GeV when mW ′ < mνR , at 95% C.L., on ′ W resonances in the t? decay channel [210]. b

16 Large extra dimensions
Models postulating the existence of large extra spatial dimensions have been proposed to solve the hierarchy problem posed by the large di?erence between the electroweak symmetry breaking scale at 1 TeV and the Planck scale, at which gravity is expected to become strong. In the original compacti?ed large extra dimensions model of Arkani-Hamed, Dimopoulos and Dvali (ADD [211]), the e?ect of the extra spatial dimensions is visible as the presence of a series of quantized energy states referred to as graviton (G) states Kaluza-Klein (KK) towers. However, the visible states are too close in mass to be distinguished individually and the coupling is small. Thus, it is only due to their very large number that the Kaluza-Klein gravitons could be observed. The direct production of gravitons, which immediately disappear into bulk space, gives rise to an excess of events with a high transverse energy jet (or photon) and large missing transverse energy.

Arnaud Duperrin

Review of Searches for Higgs Bosons and BSM Physics at the Tevatron - Page 31

k/ MPl

0.1

excluded at 95% CL

D0 PRL 95, 091801 (2005)

MD Lower Limit (TeV)

0.09 0.08 0.07 0.06 0.05

expected limit

1.6 1.4 1.2 1 0.8 0.6 2 3

CDF Run II Preliminary
CDF γ + ET (2.0 fb ) CDF Jet + ET (1.1 fb ) LEP Combined
-1 -1

excluded by precision ewk

D? 1 fb

-1

0.04 0.03 0.02 0.01 200 300 400 500 600 700 800 900 Graviton mass M1 (GeV)
Fig. 45. D? 95% C.L. upper limit on k/MPl versus graviton mass from 1 fb?1 of data for the ee + γγ ?nal states combined [214].

4

5

6

Number of Extra Dimensions
Fig. 46. Limits on the fundamental Planck scale MD for various numbers of extra dimensions from the CDF q q →γ + G and q q →jets + G [219], along with the LEP ? ? limit.

Another way to look for extra dimensions is to search for a resonance. The ?rst excited graviton mode predicted by the Randall and Sundrum (RS) model [184] could be resonantly produced at the Tevatron. The graviton is then expected to decay to fermionanti-fermion or diboson pairs. 16.1 Graviton resonances The CDF and D? Collaborations have searched for resonances in their data in many di?erent ?nal states. Since the graviton has spin 2, the branching fraction to the diphoton ?nal state is expected to be twice that of e+ e? ?nal states. The diphoton background is estimated from misidenti?ed electromagnetic objects and is extracted from the data. Results have been published by CDF [145] (D? [212]) based on 200 pb?1 (260 pb?1 ) of data. The combined ee + γγ ?nal states have been recently published by both experiments based on 1.2-1.3 fb?1 of CDF [194,213] (D? [214]) data. Limits obtained are as a function of the graviton mass and the coupling parameter (k/MP l ), as represented in Fig. 45 for D?. The CDF Collaboration derives a lower limit of 889 GeV on the graviton mass at the 95% C.L. for k/MP l =0.1. The D? combined result of both ee and γγ channels set lower masses limits of 300 (900) GeV at 95% C.L. for k/MP l = 0.01 (0.1) [214]. Recently, CDF has released a new result based on 1.1 fb?1 of data in the search for a massive object decaying to a pair of Z bosons, both of which decay to ee [215]. The cross section times branching fraction for RS gravitons that decay to Z bosons is small, leading to about one G→ZZ→eeee expected event produced in 2 fb?1 of data. For this analysis, CDF relaxed the lepton identi?cation requirements to optimize the signal sensitivity. The relaxed selection ad-

mits more background, which is then rejected by imposing kinematic requirements on the invariant masses of the two Z boson candidates. Finally, a sample in data that is kinematically similar to the signal has been used to estimate backgrounds in the signal region. No event are observed with meeee > 500 GeV for an expected background of 0 ± 0.02 in 1.1 fb?1 of data. The search is not yet sensitive to RS gravitons, so cross section limits of σ × Br(G→ZZ→eeee) 4 pb for 500 < mG < 800 GeV are set on graviton production, assuming RS couplings.

/ 16.2 Jet/γ+ET At the Tevatron, gravitons can be produced recoiling against a quark or a gluon jet [216], leading to an ex/ cess of events with a high pT jet and large ET . The resulting topology is a monojet. Similarly, gravitons can be produced directly in processes such as q q →γ + G. ? The D? Collaboration has investigated KK graviton production with a photon and missing transverse energy in 1 fb?1 of data [217]. At the 95% C.L., D? sets limits on the fundamental Planck scale (MD ) from 884 GeV to 778 GeV for 2 to 8 extra dimensions. The CDF Collaboration published results based on 368 pb?1 of monojet data [218]. Recently, the Collaboration has released a new result based on up to 2 fb?1 / of data which combines the jet/γ+ET ?nal states [219]. The optimization for the ADD model yields a photon re/ quirement of ET > 90 GeV with ET > 50 GeV and a / jet requirement of pT > 150 GeV with ET > 150 GeV. The dominant SM background to the monojet search consists of Z or W boson plus jet production, with the Z decaying to a pair of neutrinos, or the lepton from W decay escaping detection. From the absence of an excess in the data, limits on MD >1.42 (0.95)

Arnaud Duperrin

Review - Page 32
CDF Run II Data Other Overlaid events : 0.1% Pythia jγ : 0.1% Pythia bj : 3.9% Pythia jj : 95.9%

3j

6000

∑p

T

< 400 GeV
-1

CDF Run II Preliminary (2.0 fb )

4000

2000

0

1

2 3 ?R(j2,j3)

4

Fig. 47. CDF signature-based search using 2 fb?1 of data. The distribution illustrates an example of a shape discrepancy found by Vista [229] in the ?nal state consisting of exactly three jets with |η| < 2.5 and pT > 17 GeV, and with one of the jets satisfying |η| < 1 and pT > 40 GeV. This distribution illustrates the e?ect underlying most of the Vista shape discrepancies which were attributed to modeling parton radiation rather than to new physics.

are derived at 95% C.L. for the number of extra dimensions nD =2 (6). The results are shown in Fig. 46. The D? Collaboration has searched for monojet in 85 pb?1 of data [220]. The most recent D? search is in the q q →γ +G ?nal state with 1 fb?1 of data [221]. This ? analysis sets limits at 95% C.L. on MD from 884 GeV to 778 GeV for 2 to 8 extra dimensions.

17 CDF signature-based searches
Most of the searches presented so far have been optimized for signatures within a speci?c BSM model. However, it is also important to search for discrepancies with SM prediction in a model-independent approach, instead of focusing only on particular new physics scenarios. Examples of such searches have been performed by the CDF Collaboration in the channels γγ + X, where X could be an electron, a muon, a photon, a tau, or / missing transverse energy [222,223], or ?γ + ET [224, 225]. Other preliminary results have been presented for / ?nal state such as ?+γ+ET +b [226], or Z-boson +X + Y + anything, where X and Y can be leptons, photons, missing energy, or large total transverse energy [227]. These searches are based on 0.3-2.0 fb?1 of data and nothing striking has been observed yet. In particular, / the ET +photon+lepton ?nal state analysis [225] using 1 fb?1 of Run II data has not con?rmed the Run I event [228]. An even more global analysis of CDF Run II data has also been carried out to search for indications of new phenomena in 2 fb?1 of data [229]. First, a modelindependent approach (Vista) focuses on obtaining a panoramic view of the entire data landscape, and

is sensitive to new large-cross-section physics [230]. It consists of a standard set of object identi?cation criteria, which are used to identify isolated and energetic objects produced in the hard collision. All objects are required to have pT > 17 GeV. Events are partitionated into exclusive ?nal states labelled according / to the objects (e± , ?± , τ ± , γ, j, b, ET ) and compared to SM prediction. The SM prediction is obtained with pythia [28] for the generation of inclusive W, Z, γγ, γj, jj, W W, W Z, and ZZ production, while madevent [231] provides events modeling for W/Z + n jets and herwig [33] is used for top quark pair production. Detector response is modelled with the CDF simulation and a global ?t for corrections factors (such as e?ciencies and fake rates) is performed on the data. In the end, the number of events observed supports the standard model prediction with few discrepancies (see Fig. 47) attributed to modeling the parton radiation and underlying event in the data. A subset of the Vista comparison is given in Table. 4. A quasi-model-independent approach (Sleuth) emphasizes the high-pT tails and is particularly sensitive to new electroweak-scale physics [232]. Sleuth is a quasi-model-independent search technique based on the assumption that new electroweak-scale physics will manifest itself as an excess of data over the SM expectation in a particular ?nal state at large summed scalar transverse momentum ( pT ). An algorithm has also been developed to search invariant mass distributions for “bumps” that could indicate resonant production of new particles. Here again, this global search for new physics in 2 fb?1 of p? collisions reveals no indication p of physics beyond the SM. These global searches are complementary to targeted searches with speci?c signatures. However, it has been demonstrated that in order to exploit the data sample fully in term of sensitivity for a speci?c model with particularly distinct kinematic features, targeted searches out-perform these global approaches. For instance, a 115 GeV SM Higgs boson decaying to two b-tagged jets in association with a heavy electroweak gauge boson is better treated using the b? invariant b mass resonance rather than using the scalar transverse momentum sum.

Number of Events

18 Conclusion
The Tevatron Run II collider program is scheduled to run until October 2009 and possibly extend into 2010 to add an extra 25% of data, leading to an expected delivered integrated luminosity of about 8-9 fb?1 . The search for the Higgs boson and physics beyond the standard model will greatly bene?t from this additional integrated luminosity. The accelerator performance is excellent and provides a great opportunity for the CDF and D? experiments to meet or exceed their stated physics goals. Both CDF and D? experiments have now surpassed the 4 fb?1 in delivered luminosity. While the ATLAS and CMS experiments at the LHC should be in good position to discover the Higgs boson on a time scale similar to the one considered at

Arnaud Duperrin

Review of Searches for Higgs Bosons and BSM Physics at the Tevatron - Page 33

??? ?? ?? ? ? ? ?? ???? ?? ? ? ? ?? ? ?? ? ????× ?? ? ?? ?× ???

Table 4. A subset of the model-independent search (Vista), which compares CDF Run II data with the SM prediction in 2 fb?1 of data [229]. Events are partitioned into exclusive ?nal states based on standard CDF particle identi?cation criteria. Final states are labelled in this table according to the number and types of objects present, and are ordered according to decreasing discrepancy between the total number of events expected and the total number observed in the data. Only statistical uncertainties on the background prediction have been included in this Table.

???? ? ? ? ? ? ?? ? ? ?? ? ??? ? ?? ? ·? ? ?? ? ? ??? ·? ? ? ???? ? ?? ? ? ?? ? ? ??????? ??? ?? ? ? ??????? ? ? ? ? ?? ?? ? ? ? ??? ·? ? ?§ ?? ? ? ? ? ?? ? ? ? ?? ?? ? ? ?? ? ?? ?? ? ? ? ? ?? ? ?? ? ? ? ? ???? ·? ? ? ??????? ? ? ? ? ?? ?? ? ? ??????? ?? ? ? ? ? ?? ? ? ? ??????? ?? ? ? ? ?? ?? ? ?? ? ?? ? ?? ?? ?? ? ?? ? ?? ?? ?? ? ? ·? ? ? ?? ? ? ? ??? ? ?? ? ? ? ?? ? ? ?? ?? ? ? ? ???? ? ? ? ? ? ??????? ? ?? ? ?? ? ? ?? ?? ? ? ???? ? ? ? ? ? ? ??????? ? ????? ? ? ???? ?? ???? ? ? ? ? ? ? ?? ? ? ? ?? ? ?? ? ? ?? ? ? ? ? ???? ? ? ?? ? ? ?? ? ?§ ? ? ? ? ? ?? ? ?? ? ? ? ? ? ? ???? ? ? ? ? ? ? ?? ? ? ? ??????? ? ? ??? ? ? ? ? ?? ?? ? ? ? ? ? ? ???? ?? ? ? ? ???? ? ? ? ? ? ? ? ??????? ? ? ?? ? ?? ? ? ? ?? ? ? ?? ?? ? ? ? ? ?? ? ? ? ?? ? ? ? ?? ? ? ? ? ?? ? ? ? ?? ?? ? ? ? ? ? ?? ? ?? ? ? ?§ ? ? ?? ? ? ? ? ??? ? ?? ? ?? ?? ? ? ? ? ? ? ? ? ? ? ? ?? ?? ? ? ? ? ??? ?? ?? ? ? ? ?? ? ? ? ? ? ???? ? ? ? ? ? ? ? ? ? ? ? ??????? ? ? ? ?? ? ? ? ? ?? ? ?? ? ? ? ? ? ? ??? ?? ?? ? ? ?? ? ? ? ?? ? ? ? ???? ?? ? ? ? ?

? ? ?? ? ?

?

???? ? ? ???? ? ? ? ? ??????? ?? ? ??? ?? ? ? ?? ? ? ? ? ?? ? ?? ? ? ? ?? ? ??? ? ?? ?? ???? ? ? ?§ ? ? ???? ? ?? ? ? ? ? ? ? ??? ? ? ?? ?? ? ? ? ?? ? ? ?? ? ? §? ?? ?? ? ?§ ? ? ?? ? ? ?? ? ????? ? ? ?? ? ?? ? ? ? ??§ ?? ? ? ? ?? ?? ??? ? ???? ? ? ??????? ??? ??? ? ? ?? ? ? ? ??????? ? ? ? ? ???? ? ?? ? ? ?? ? ? ? ???? ? ?? ? ? ? ?? ?? ? ? ? ? ? ?? ? ? ??? ?? ? ?? ?? ? ? ? ?? ?? ? ? ? ? ? ???? ? ? ? ?? ? ? ? ???? ? ?? ? ? ? ? ? ? ? ? ? ? ?? ?? ?? ? ? ? ?? ? ?? ? ? ? ? ? ? ?? ? ?? ? ?? ?? ? ? ? ? ? ? ?? ? ? ??? ? ? ? ??? ? ? ??? ? ?§ ? ?? ?? ? ? ? ? ? ?? ? ?§ ?? ? ? ? ?? § ? ?? ?? ? ? ?? ? ? ?? ??? ?? ? ?? ? ?? ? §? ? ? ? ? ? §? ? ???? ?§ ? ? ?? ? ? ??? ? ?? ? ? ?? ? ?? ? ?? ? ? ? ? ??? ? ??? ? § ? ??? ? ? ? ? ? ???? ?? ?? ? ? ? ? ? ? ? ?? ? ? ? ? ? ?? ? ????? ????? ? ? ?§ ? ?? ?? ? ?? ? ? ?? § ? ?? ? ? ?? ?? ? ? ?? ??? ? ? ? ?? ? ? ? ? ? ? ?? ?? ? ? ? ??? ?

? ? ?? ?

?

? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ?

? §? ? §? ?§ ? ? ? ? ? ? ?? § ?? ? ?? ? ?? ? ?? ?? ? ?? § ?? ? ? ? ?? ?? ? ?? §? ?? § ?? ?§ ?? § ?? ? ?? ?? ? ?? ? §? ?? ?§ ? ?? ? § ? ? ?? § ?? ? ?? ? ?? ?? ? §? ? ?? ? § ? ? ?§ ? §? ? §? ? ? §? ? ?§ ? §?? ? §? ? §? ? §? ? §? ?§ ?§

?? ?? ? ? ?? ? ?? ? ? ? ? ???? ? ?? ? ?? ?? ? ?? ? ? ? ??? ? ?? ? ?? ? ? ?? ? ? ? ? ? ? ?? ? ?? ?? ? ? ? ? ? ? ?? ? ? ? ??? ? ???? ?? ? ? ? ? ?? ? ? ?? ?? ?? ? ? ? ? ?? ?? ? ? ? ?? ? ? ? ? ? ? ? ???? ?? ? ?? ? ?? ?? ? ? ? ?? ? ?? ? ?? ? ? ? ?? ? ?? ? ? ? ?? ?? ? ?? ? ? ??? ? ?? ? ? ? ? ? ? ?? ? ? ? ? ?? ??? ?? ??? ??? ?? ?????? ? ? ? ? ? ?? ?? ?? ? ? ? ?? ? ? ? ??? ? ? ??? ?? ??? ? ? ?? ? ? ?? ?? ? ? ?? ?? ? ? ?? ? ? ? ? ? ??? ?? ?? ? ?? ? ? ??? ? ? ? ? ? ? ?? ?? ? ?? ? ? ? ? ?? ?? ? ? ? ? ???? ?? ? ? ? ? ???? ? ?? ? ? ??????? ? ?? ? ? ? ???? ??? ? ??? ? ? ? ? ??????? ? ? ? ? ??

? ? ?? ?

?

????

? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ?

Arnaud Duperrin the Tevatron, observation in the H→b? decay chanb nel will be extremely di?cult at the LHC. Given the importance of observing the Higgs boson in its main decay mode, searches at the Tevatron have thus to be viewed as complementary to, rather than in competition with, the Higgs boson search at the LHC. Failure to observe the Higgs boson in the mass range considered would also be a very important result, as it would indicate a breakdown of the standard model and give directions for alternative theories. Current electroweak data point to the existence of a light Higgs, which means that the so-far elusive Higgs particle is within reach of Tevatron. Soon the LHC will also exploit its potential for discovery of new particles. However, a light Higgs boson corresponds to the less favorable scenario at LHC for an early discovery. In addition, it may take some time to operate the ATLAS and CMS detectors and to understand the new data. At the Tevatron, a Higgs boson in this mass range can only be convincingly observed if the integrated luminosity delivered is su?ciently large (8-9 fb?1 ) and the current analyses continue to improve their sensitivity. Furthermore, if its mass is heavier than ≈140 GeV, the MSSM will be ruled out, a conclusion which applies to the majority of supersymmetric models. This review has summarized the searches for Higgs bosons and beyond-the-standard-model physics at the Tevatron that have been conducted until May 2008. However, despite all e?orts, no signi?cant deviations from the standard model predictions have been found to date based on data samples corresponding to integrated luminosities of up to 2.5 fb?1 . Of course, this should not be taken to mean absence of new physics in these data, for there are still a number of fb?1 of frontier physics ahead of us at the Tevatron.

Review - Page 34

4. H.E. Haber and G.L. Kane, Phys. Rep. 117, 75 (1985). 5. H.P. Nilles, Phys. Rep. 110, 1 (1984). 6. CDF Collaboration, CDF physics results page: http://www-cdf.fnal.gov/physics/physics.html 7. D? Collaboration, D? physics results page: http://www-d0.fnal.gov/Run2Physics/WWW/results.htm 8. CDF Collaboration, Phys. Rev. D71, 032001 (2005); J. Phys. G34, 2457 (2007). 9. D? Collaboration, Nucl. Instrum. Methods A565, 463 (2006). 10. CDF Collaboration, Nucl. Instrum. Methods A447, 1 (2000); ibid., 453, 84 (2000). 11. CDF Collaboration, Nucl. Instrum. Methods A526, 249 (2004). 12. CDF Collaboration, Nucl. Instrum. Methods A566, 375 (2006), and references therein. 13. G.C. Blazey et al., in Proceedings of the Workshop: “QCD and Weak Boson Physics in Run II,” edited by U. Baur, R.K. Ellis, and D.Zeppenfeld (Fermilab, Batavia, IL, 2000), p. 47; see Sec. 3.5 for details. 14. A. Djouadi, The anatomy of electro-weak symmetry breaking. I: The Higgs boson in the standard model, arXiv:hep-ph/0503172v2 (2005). 15. C. F. Kolda, H. Murayama, J. High Energy Phys. 0007, 035 (2000). 16. CDF and D? Collaborations, Combination of CDF and D? results on the mass of the top quark, CDF Note 9225, D? Note 5626 (2008). 17. LEP Collaborations and LEP Electroweak Working Group, Precision electroweak measurements and constraints on the standard model, arXiv:hepex/0712.0929v2 (2007). 18. CDF Collaboration, Phys. Rev. Lett. 99, 151801 (2007) and CDF Collaboration, First Run II measurement of the W boson mass, submitted to Phys. Rev. D, arXiv:hep-ex/0708.3642v1 (2007). 19. LEP Electroweak Working Group, http://lepewwg.web.cern.ch/LEPEWWG/ 19 Acknowledgments 20. LEP Collaborations, Phys. Lett. B565, 61 (2003). I would like to thank my colleagues both at Fermi21. U. Aglietti et al., Tevatron-for-LHC Report: Higgs, lab and at other collaborating institutions, especially arXiv:hep-ph/0612172v2 (2007). those who operate the Tevatron accelerator and con22. T. Han, G. Valencia, S. Willenbrock, Phys. Rev. Lett. struct, maintain, and calibrate the CDF and D? detec69, 3274 (1992); E.L. Berger and J. Campbell, Phys. Rev. D70, 073011 (2004); T. Figy, C. Oleari, D. Zeptors, essential for any physics analysis reported here. penfeld, Phys. Rev. D68, 073005 (2003). I wish to thank all the colleagues for providing valu23. W. Beenakker et al., Phys. Rev. Lett. 87, 201805 able input and/or proofreading this document, in par(2001); L. Reina and S. Dawson, Phys. Rev. Lett. ticular I would like to address special thanks to Chris 87, 201804 (2001); S. Dawson, L.H. Orr, L. Reina, Hays, Gavin Davies, Gregorio Bernardi, and Matthew D. Wackeroth, Phys. Rev. D67, 071503 (2003). Herndon. I am also grateful to Todd Adams, Volker B¨ scher, Dmitri Denisov, Monica D’onofrio, Wade Fisher, 24. R.V. Harlander and W.B. Kilgore, Phys. Rev. u D68, 013001 (2003); J. Campbell, R.K. Ellis, Aurelio Juste, Stefan S¨ldner-Rembold, Patrice Verdier, o F. Maltoni, S. Willenbrock, Phys. Rev. D67, and Darien Wood for their suggestions and comments 095002 (2003); S. Dawson, C.B. Jackson, L. Reina, during the preparation of this review. D. Wackeroth, Phys. Rev. Lett. 94, 031802 (2005); S. Dittmaier, M. Kr¨mer, M. Spira, Phys. Rev. D70, a 074010 (2004); S. Dawson, C.B. Jackson, L. Reina, References D. Wackeroth, Phys. Rev. D69, 074027 (2004). 25. K.A. Assamagan et al., The Higgs Working Group: 1. P. W. Higgs, Phys. Lett. 12, 132 (1964). Summary Report 2003, arXiv:hep-ph/0406152v1 2. C. Mu?oz, Int. J. Mod. Phys. A19, 3093 (2004). n (2004). 3. For reviews on supersymmetric theories, see J. Wess and B. Zumino, Nucl. Phys. B70, 39 (1974); P. Fayet 26. O. Brein, A. Djouadi, R. Harlander, Phys. Lett. and S. Ferrara, Phys. Rep. 32, 249 (1977); H.P. Nilles, B579, 149 (2004); M.L. Ciccolini, S. Dittmaier, Phys. Rep. 110, 1 (1984). M. Kr¨mer, Phys. Rev. D68, 073003 (2003). a

Arnaud Duperrin

Review of Searches for Higgs Bosons and BSM Physics at the Tevatron - Page 35
46. D? Note 5586, Search for the standard model Higgs boson in the HZ→bbνν channel in 2.1 fb?1 of p? colp √ lisions at s = 1.96 TeV, (2008). 47. CDF Note 9166, Neural network search for stan/ dard model Higgs boson in ET plus jets channel with 1.7 fb?1 , (2008). 48. CDF Note 8742, Search for ZH→??b? in 1 fb?1 of b CDF Run 2 data, (2007). 49. D? Note 5482, Search for ZH→??b? in p? collisions b p √ at s = 1960 GeV, (2007). 50. D? Collaboration, Phys. Lett. B655, 209 (2007). 51. H.E. Haber, G.L. Kane, T. Sterling, Nucl. Phys. B161, 493 (1979); J.F. Gunion, R. Vega, J. Wudka, Phys. Rev. D42, 1673 (1990); J.L. Basdevant, E.L. Berger, D. Dicus, C. Kao, S. Willenbrock, Phys. Lett. B313, 40 (1993); V. Barger, N.G. Deshpande, J.L. Hewett, T.G. Rizzo,arXiv:hepph/9211234 (1992); P. Bamert and Z. Kunszt, Phys. Lett. B306, 335 (1993); A.G. Akeroyd, Phys. Lett. B368, 89 (1996); M.C. Gonzalez-Garcia, S.M. Lietti, S.F. Novaes, Phys. Rev. D57, 7045 (1998); A. Barroso, L. Brucher, R. Santos, Phys. Rev. D60, 035005 (1999); L. Brucher and R. Santos, Eur. Phys. J. C12, 87 (2000). 52. B. Dobrescu, Phys. Rev. D63, 015004 (2001); B. Dobrescu, G. Landsberg, K. Matchev, FERMILABPUB99/324-T. 53. L. Hall and C. Kolda, Phys. Lett. B459, 213 (1999); H. Cheng, B.A. Dobrescu, C.T. Hill, Nucl. Phys. B589, 249 (2000). 54. D? Collaboration, Phys. Rev. Lett. 97, 151804 (2006). 55. CDF Note 7307, Search for the W h production using high-pT isolated like-sign dilepton events in Run II with 1.9 fb?1 , (2008). 56. D? Note 5485, Search for the Associated Higgs Boson Production p?→W H→W W W (?)→?± ?± , (2007). p 57. CDF Collaboration, Phys. Rev. Lett. 97, 081802 (2006). 58. D? Collaboration, Phys. Rev. Lett. 96, 011801 (2006). 59. CDF Note 9236, Search for Higgs to W W ? production using a combined matrix element and neural network technique at Tevatron using 2.4 fb?1 of data, (2008). 60. D? Note 5537, Search for the Higgs Boson in ′ ′ H→W W ? →ll (l, l = e, mu) decays with 1.7 fb?1 of Data at D?, (2007). 61. D? Note 5624, Search for the Higgs boson in ′ ′ H→W W ? →ll (l, l = e, mu) decays with 1.2 fb?1 at D? in Run IIb, (2008). 62. D? Collaboration, Search for hf → γγ with the D? √ detector at s = 1.96 TeV, submitted to Phys. Rev. Lett., arXiv:hep-ex/0803.1514v12008. 63. D? Note 5601, Search for a light Higgs boson in γγ ?nal states at D?, (2008). 64. CDF Note 9248, Search for the SM Higgs Boson using τ lepton. Simultaneous Search for W H/ZH/V BF/ggH in 2t’s+2jets event, (2008). 65. Tevatron New Phenomena & Higgs Working Group (TEVNPHWG), Combined CDF and D? upper limits on standard model Higgs boson production, CDF Note 8961, D? Note 5536, FERMILAB-PUB-07-656E (2007), arXiv:hep-ex/0712.2383v1. 66. Tevatron New Phenomena & Higgs Working Group (TEVNPHWG), Combined CDF and D0 upper limits on standard model Higgs boson production with

27. D. Graudenz, M. Spira, P.M. Zerwas, Phys. Rev. Lett. 70, 1372 (1993); S. Catani, D. de Florian, M. Grazzini, P. Nason, J. High Energy Phys. 0307, 028 (2003); R.V. Harlander and W.B. Kilgore, Phys. Rev. Lett. 88, 201801 (2002); C. Anastasiou and K. Melnikov, Nucl. Phys. B646, 220 (2002); C. Anastasiou, K. Melnikov, F. Petriello, Phys. Rev. Lett. 93, 262002 (2004); U. Aglietti, R. Bonciani, G. Degrassi, A. Vicini, Phys. Lett. B595, 432 (2004); G. Degrassi and F. Maltoni, Phys. Lett. B600, 255 (2004). 28. T. Sj¨strand et al., Comput. Phys. Commun. 135, o 238 (2001); T. Sj¨strand, L. Lonnblad, S. Mrenna, o PYTHIA 6.2: Physics and manual, arXiv:hepph/0108264v1 (2001). 29. H.L. Lai et al., Eur. Phys. J. C12, 375 (2000); Phys. Rev. D55, 1280 (1997). 30. A. Djouadi, J. Kalinowski, M. Spira, Comput. Phys. Commun. 108, 56 (1998); arXiv:hep-ph/9704448 (1997). 31. M.L. Mangano, M. Moretti, F. Piccinini, R. Pittau, A.D. Polosa, J. High Energy Phys. 0307, 001 (2003); arXiv:hep-ph/0206293v2 (2003). 32. S. Frixione and B.R. Webber, J. High Energy Phys. 06, 029 (2002); arXiv:hep-ph/0204244v2 (2002). 33. G. Corcella, I.G. Knowles, G. Marchesini, S. Moretti, K. Odagiri, P. Richardson, M.H. Seymour, B.R. Webber, J. High Energy Phys. 0101, 010 (2001); arXiv:hep-ph/0011363v3 (2002). 34. A. Pukhov, E. Boos, M. Dubinin, V. Edneral, V. Ilyin, D. Kovalenko, A. Kryukov, V. Savrin, S. Shichanin, A. Semenov, CompHEP: A package for evaluation of Feynman diagrams and integration over multi-particle phase space. User’s manual for version 33, arXiv:hepph/9908288v2 (2000). 35. J. Campbell and R.K. Ellis, Phys. Rev. D60, 113006 (1999), arXiv:hep-ph/9905386v2 (1999). 36. T. Scanlon, FERMILAB-THESIS-2006-43. 37. L. Breiman et al., Classi?cation and Regression Trees, Wadsworth (1984); Y. Freund and R.E. Shapire, Experiments with a new boosting algorithm, in Machine Learning: Proceedings of the Thirteenth International Conference, pp. 148-156 (1996); D? Collaboration, Phys. Rev. Lett. 98, 181802 (2007). 38. CDF Collaboration, Strong evidence of ZZ produc√ tion in p? collisions at s = 1.96 TeV, accepted to p Phys. Rev. Lett., arXiv:hep-ex/0801.4806v1 (2008). 39. D? Note 5620, ZZ→??ν ν production in p? collisions ? p √ at s = 1.96 TeV, (2008). 40. CDF Collaboration, Phys. Rev. Lett. 100, 041801 (2008). 41. D? Collaboration, A combined search for the stan√ dard model Higgs boson at s = 1.96 TeV, Phys. Lett. B663, 26 (2008). 42. CDF Note 9219, Search for standard model Higgs boson production in association with W ± boson at CDF with 1.9 fb?1 , (2008). 43. D? Note 5472, Search for WH Production using a √ neural network approach in p? Collisions at s = p ?1 1.96 TeV with 1.7 fb of Data, (2007). 44. D? Collaboration, Phys. Rev. Lett. 97, 161803 (2006). 45. CDF Collaboration, Search for the Higgs boson in events with missing transverse energy and b quark √ jets produced in proton-antiproton collisions at s = 1.96 TeV, submitted to Phys. Rev. Lett., arXiv:hepex/0802.0432v1 (2008).

Arnaud Duperrin
up to 2.4 fb?1 of data, CDF Note 9290, D? Note 5645, FERMILAB-PUB-08-069-E (2008); arXiv:hepex/0804.3423v1 (21 April 2008). CDF Note 8941, Combined upper limits on standard model Higgs boson production, (2007). D? Note 5625, Combined upper limits on standard model Higgs boson production from the D? experiment in 1.0-2.3 fb?1 , (2008). T. Junk, Nucl. Instrum. Methods A434, 435 (1999); A. Read, in “First Workshop on Con?dence Limits”, CERN Report No. CERN-2000-005 (2000). W. Fisher, FERMILAB-TM-2386-E (2007). J.R Espinosa and M. Quiros, Phys. Lett. B266, 389 (1991); R. Hemp?ing and A. Hoang, Phys. Lett. B331, 99 (1994); J.A Casa, J. Espinosa, M. Quiros and A. Riotto, Nucl. Phys. B436, 3 (1995); (E) B439, 466 (1995); M. Carena, J. Espinosa, M. Quiros, C.E.M. Wagner, Phys. Lett. B355, 209 (1995); M. Carena, M. Quiros, C.E.M. Wagner, Nucl. Phys. B461, 407 (1996); S. Heinemeyer, W. Hollik, G. Weiglein, Phys. Rev. D58, 091701 (1998), Phys. Lett. B440, 296 (1998), J. High Energy Phys. 0006, 009 (2000); J.R Espinosa and R.J. Zhang, Nucl. Phys. B586, 3 (2000); A. Brignole, G. Degrassi, P. Slavich, F. Zwirner, Nucl. Phys. B631, 195 (2002), Nucl. Phys. B643, 79 (2002); S. Heinemeyer, W. Hollik, H. Rzehak, G. Weiglein, Eur. Phys. J. C39, 465 (2005). S. Heinemeyer, W. Hollik, G. Weiglein, Eur. Phys. J. C9, 343 (1999), Comput. Phys. Commun. 124, 76 (2000); G. Degrassi, S. Heinemeyer, W. Hollik, P. Slavich, G. Weiglein, Eur. Phys. J. C28, 133 (2003); M. Frank et al., J. High Energy Phys. 0702, 047 (2007). M. Carena and H.E. Haber,Prog. Part. Nucl. Phys. 50, 63 (2003). S. Bertolini, F. Borzumati, A. Masiero, G. Ridol?, Nucl. Phys. B353, 591 (1991); K.S. Babu and C. F. Kolda, Phys. Rev. Lett. 84, 228 (2000); C. Hamzaoui, M. Pospelov, M. Toharia, Phys. Rev. D59, 095005 (1999); G. Isidori and A. Retico, J. High Energy Phys. 0111, 001 (2001); A.J. Buras, P.H. Chankowski, J. Rosiek, L. Slawianowska, Phys. Lett. B546, 96 (2002); A.J. Buras, P.H. Chankowski, J. Rosiek, L. Slawianowska, Nucl. Phys. B659, 3 (2003); A. Dedes and A. Pilaftsis, Phys. Rev. D67, 015012 (2003); G. D’Ambrosio, G.F. Giudice, G. Isidori, A. Strumia, Nucl. Phys. B645, 155 (2002); M. Dugan, B. Grinstein, L.J. Hall, Nucl. Phys. B255, 413 (1985); J. Foster, K.I. Okumura, L. Roszkowski, J. High Energy Phys. 0508, 094 (2005). M. Carena, S. Heinemeyer, C. E. M. Wagner, and G. Weiglein, Eur. Phys. J. C26, 601-607 (2003). J.R. Ellis, S. Heinemeyer, K.A. Olive, A.M. Weber, G. Weiglein, J. High Energy Phys. 0708, 083 (2007). ALEPH, DELPHI, L3, and OPAL Collaborations, The LEP Working Group for Higgs Bosons Searches, Eur. Phys. J. C47, 547 (2006). O. Buchmueller et al., Phys. Lett. B657, 87 (2007). J. Campbell, R. K. Ellis, F. Maltoni, S. Willenbrock, Phys. Rev. D67, 095002 (2003). S. Dawson, C. B. Jackson, L. Reina, D. Wackeroth, Mod. Phys. Lett. A21, 89 (2006). D? Collaboration, Phys. Rev. Lett. 95, 151801 (2005).

Review - Page 36
82. D? Note 5503, Search for neutral Higgs bosons at high tan β in multijet events, (2006). 83. CDF Note 8954, Search for Higgs bosons produced in association with b-quarks, (2007). 84. CDF Note 9284, Search for Higgs bosons produced in association with b-quarks , (2008). 85. D? Collaboration, Search for neutral Higgs √ bosons s = in multi-b-jet events in p? collisions at p 1.96 TeV, submitted to Phys. Rev. Lett., arXiv:hepex/0805.3556v1 (2008). 86. M. Carena, S. Heinemeyer, C.E.M. Wagner, G. Weiglein, Eur. Phys. J. C45, 797 (2006). 87. M. Spira, higlu: A program for the calculation of the total Higgs production cross section at hadron colliders via gluon fusion including QCD corrections, arXiv:hep-ph/9510347v1 (1995). 88. CDF Collaboration, Phys. Rev. Lett. 96, 011802 (2006). 89. D? Collaboration, Phys. Rev. Lett. 97, 121802 (2006). 90. CDF Note 9071, Search for neutral MSSM Higgs bosons decaying to tau pairs with 1.8 fb?1 of data, (2007). 91. D? Collaboration, Search for Higgs bosons decaying to tau pairs in p? collisions with the D? dep tector, submitted to Phys. Rev. Lett., arXiv:hepex/0805.2491v1 (2008). 92. LEP Higgs Working Group, Note 2004-01 (2004). 93. CDF Collaboration, Phys. Rev. Lett. 96, 042003 (2006). 94. CDF Note 8353, Search for anomalous tau production in b-tagged top quark events, (2006). 95. G. Senjanovic and R.N. Mohapatra, Phys. Rev. D12, 1502 (1975). 96. G. B. Gelmini and M. Roncadelli, Phys. Lett. B99, 411 (1981). 97. N. Arkani-Hamed, A.G. Cohen, E. Katz, A.E. Nelson, J. High Energy Phys. 0207, 034 (2002). 98. CDF Collaboration, Phys. Rev. Lett. 93, 221802 (2004). 99. D? Collaboration, Phys. Rev. Lett. 93, 141801 (2004). 100. CDF Note 8050, Search for p?→H ++ H ?? →?+ τ + ?? τ ? , (2006). p 101. D? Collaboration, Search for pair production of doubly-charged Higgs bosons in the H ++ H ?? →?+ ?+ ?? ?? ?nal state at D?, submitted to Phys. Rev. Lett., arXiv:hep-ex/0803.1534v1 (2008). 102. OPAL Collaboration, Phys. Lett. B526, 221 (2002); OPAL Collaboration, Phys. Lett. B295, 347 (1992); L3 Collaboration, Phys. Lett. B576, 18 (2003); DELPHI Collaboration, Phys. Lett. B552, 127 (2003). 103. CDF Collaboration, Phys. Rev. Lett. 95, 071801 (2005). 104. D? Note 5067, Search for fermiophobic Higgs boson in 3γ + X events, (2007). 105. S. Weinberg, Phys. Rev. D13, 974 (1976); L. Susskind, Phys. Rev. D20, 2619 (1979). 106. D? Collaboration, Phys. Rev. Lett. 98, 221801 (2007). 107. CDF Note 9302, Search for technicolor particles produced in association with W ± boson with 1.9 fb?1 at CDF, (2008).

67. 68.

69.

70. 71.

72.

73. 74.

75. 76. 77.

78. 79. 80. 81.

Arnaud Duperrin

Review of Searches for Higgs Bosons and BSM Physics at the Tevatron - Page 37
135. CDF Collaboration, Phys. Rev. D71, 031104 (2005). 136. D? Collaboration, Phys. Rev. Lett. 94, 041801 (2005). 137. V. Buescher et al., for the CDF and D? Collaborations, Combination of CDF and D? limits on a gauge mediated SUSY model using diphoton and missing transverse energy channel, arXiv:hepex/0504004v12005. 138. B.C. Allanach et al., Eur. Phys. J. C25, 113 (2002). 139. D? Collaboration, Phys. Lett. B659, 856 (2008). 140. CDF Collaboration, Phys. Rev. Lett. 98, 131804 (2007). 141. D? Collaboration, Phys. Lett. B638, 441 (2006). 142. CDF Note 7835, Search for pair production of scalar top quarks decaying to a τ lepton and a b quark, (2005). 143. CDF Collaboration, Phys. Rev. Lett. 96, 211802 (2006). 144. D? Collaboration, Search for sneutrino particles √ s = in e+mu ?nal states in p? collisions at p 1.96 TeV., submitted to Phys. Rev. Lett., arXiv:hepex/0711.3207v2 (2007). 145. CDF Collaboration, Phys. Rev. Lett. 95, 252001 (2005). 146. CDF Collaboration, Phys. Rev. Lett. 95, 131801 (2005). 147. D? Collaboration, Phys. Rev. Lett. 97, 111801 (2006). 148. M. Byrne, C. Kolda, P. Regan, Phys. Rev. D66, 075007 (2002). 149. M.J. Strassler and K.M. Zurek, Echoes of a hidden valley at hadron colliders, arXiv:hep-ph/0604261 (2006). 150. NuTeV Collaboration, Phys. Rev. Lett. 87, 041801 (2001). 151. D? Collaboration, Phys. Rev. Lett. 97, 161802 (2006). 152. A. De Rujula, S. L. Glashow, and U. Sarid, Nucl. Phys. B333, 173 (1990). 153. CDF Note 8701, Search for charged massive stable particles, (2007). 154. H. Frampton, P.Q. Hung, M. Sher, Phys. Rep. 330, 263 (2000). 155. CDF Note 7244, Search for long-lived parents of the Z boson, (2004). 156. D? Note 5454, Search for long-lived particles decaying into Z bosons, (2007). 157. N. Arkani-Hamed, S. Dimopoulos, G.F. Giudice, A. Romanino, Nucl. Phys. B709, 3 (2005). 158. A. Arvanitaki, S. Dimopoulos, A. Pierce, S. Rajendran, J. Wacker, Stopping gluinos, arXiv:hepph/05062422005. 159. D? Collaboration, Phys. Rev. Lett. 99, 131801 (2007). 160. W. Buchmuller and D. Wyler, Phys. Lett. B177, 377 (1986). 161. H. Georgi and S.L. Glashow, Phys. Rev. Lett. 32, 438 (1974). 162. J.L. Hewett and T.G. Rizzo, Phys. Rep. 183, 193 (1989). 163. B. Schrempp and F. Schrempp, Phys. Lett. B153, 101 (1985). 164. CDF Collaboration, Phys. Rev. D72, 051107 (2005). 165. CDF Collaboration, Phys. Rev. D71, 112001 (2005), Erratum-ibid., D71, 119901 (2005).

108. D? Collaboration, Phys. Rev. Lett. 95, 151805 (2005). 109. CDF Collaboration, Phys. Rev. D77, 052002 (2008). 110. CDF Collaboration, Phys. Rev. Lett. 98, 221803 (2007). 111. CDF Collaboration, Phys. Rev. Lett. 99, 191806 (2007). 112. D? Note 5464, Search for the associated production of chargino and neutralino in ?nal states with two electrons and an additional lepton, (2007). 113. CDF Note 9176, A uni?ed search for associated production of chargino-neutralino at CDF using leptons, (2008). 114. LEP SUSY Working Group, ibid., note LEPSUSYWG/01-03.1. 115. H. Baer, F.E. Paige, S.D. Protopescu, X. Tata, ISAJET : A monte carlo event generator for pp, pp, and e+ e? reactions, see for instance arXiv:hep? ex/0312045v1. 116. W. Beenakker, M. Kr¨mer, T. Plehn, M. Spira, a P.M. Zerwas, Nucl. Phys. B515, 3 (1998). 117. D? Collaboration, Phys. Lett. B660, 449 (2008). 118. CDF Note 9229, Search for gluino and squark production in multijets plus missing ET ?nal State, (2008). 119. J. Pumplin, D.R. Stump, J. Huston, H.L. Lai, P. Nadolsky, W.K. Tung , J. High Energy Phys. 0207, 012 (2002); D. Stump, J. Huston, J. Pumplin, W.K. Tung, H.L. Lai, S. Kuhlmann, J.F. Owens, J. High Energy Phys. 0310, 046 (2003). 120. LEP SUSY Working Group, ibid., note LEPSUSYWG/02-06.2. 121. D? Note 5468, Search for squark production in events with jets, hadronically decaying taus and missing √ transverse energy with the D? detector at s = 1.96 TeV in the Run IIa data, (2007). 122. D? Collaboration, Search for scalar top quarks in the acoplanar charm jets and missing transverse energy √ ?nal state in p? collisions at s = 1.96 TeV, accepted p by Phys. Lett. B, arXiv:hep-ex/0803.2263v1 (2008). 123. D? Collaboration, Phys. Lett. B645, 119 (2007). 124. CDF Collaboration, Phys. Rev. D76, 072010 (2007). 125. D? Collaboration, Phys. Rev. Lett. 97, 171806 (2006). 126. CDF Collaboration, Phys. Rev. Lett. 96, 171802 (2006). 127. CDF Note 9332, Search of gluino-mediated sbottom production in the MET+b-jet sample, (2008). 128. D? Note 5438, Search for scalar top admixture in the √ ? t lepton+jets ?nal state at s = 1.96 TeV in 1 fb?1 of D? Data, (2007). 129. D? Collaboration, Phys. Lett. B659, 500 (2008). 130. D? Note 5598, Search for pair production of the supersymmetric partner of the top quark in the ?? t1 t1 →b? ± ?± ν ν decay channel at D?, (2008). be ?? ? 131. J. Feng and T. Moroi, Phys. Rev. D58, 035001 (1998). 132. D? Note 4746, A search for charged massive stable particles at D?, (2005). 133. J. Gunion and S. Mrenna, Phys. Rev. D62, 015002 (2000). 134. CDF Collaboration, Phys. Rev. Lett. 99, 121801 (2007); Search for heavy, long-lived neutralinos that decay to photons at CDF II using photon timing, submitted to Phys. Rev. D, arXiv:hep-ex/0804.1043v1 (2008).

Arnaud Duperrin
166. D? Collaboration, Phys. Rev. D71, 071104 (2005). 167. D? Collaboration, Phys. Lett. B640, 230 (2006). 168. CDF Note 9329, Search for new physics in the exclusive dijet plus missing ET event sample, (2008). 169. CDF Collaboration, Phys. Rev. D73, 051101 (2006). 170. D? Collaboration, Phys. Lett. B636, 183 (2006). 171. D? Note 5370, Search for second generation scalar leptoquarks in the ?νjj ?nal state with the D? detector, (2007). 172. D? Note 5447, Search for third generation scalar leptoquarks using the τ bτ b ?nal state, (2007). 173. D? Collaboration, Phys. Rev. Lett. 99, 061801 (2007). 174. CDF Collaboration, Search for third generation √ s = vector leptoquarks in p? collisions at p 1.96 TeV, submitted to Phys. Rev. D, arXiv:hepex/0706.2832v1 (2007). 175. D? Collaboration, Phys. Lett. B647, 74 (2007). 176. H. Terazawa, M. Yasue, K. Akama, M. Hayashi, Phys. Lett. B112, 387 (1982); F.M. Renard, Nuovo. Cimento. A77, 1 (1983); A. De Rujula, L. Maiani, R. Petronzio, Phys. Lett. B140, 253 (1984); E.J. Eichten, K.D. Lane, M.E. Peskin, Phys. Rev. Lett. 50, 811 (1983). 177. D? Collaboration, Phys. Rev. D77, 091102(R) (2008). 178. CDF Collaboration, Phys. Rev. Lett. 94, 101802 (2005). 179. CDF Collaboration, Phys. Rev. Lett. 97, 191802 (2006). 180. D? Collaboration, Phys. Rev. D73, 111102 (2006). 181. U. Baur, M. Spira, P. Zerwas, Phys. Rev. D42, 8158 (1990). 182. D? Collaboration, Phys. Rev. D74, 011104 (2006). 183. CDF Note 9246, Search for new particles decaying to √ dijets in p? collisions at s = 1.96 TeV, (2008). p 184. L. Randall and R. Sundrum, Phys. Rev. Lett. 83, 3370 (1999); ibid., 83, 4690 (1999). 185. K.D. Lane and M.V. Ramana, Phys. Rev. D44, 2678 (1991); E. Eichten and K.D. Lane, Phys. Lett. B327, 129 (1994); K. Lane and S. Mrenna, Phys. Rev. D67, 115011 (2003). 186. J. Bagger, C. Schmidt, S. King, Phys. Rev. D37, 1188 (1988); P.H. Frampton and S.L. Glashow, Phys. Lett. B190, 157 (1987). 187. CDF Collaboration, Phys. Rev. D76, 072006 (2007). 188. CDF Note 9164, A search for massive gluon decaying to top pair in lepton+jet channel, (2008). ′ 189. CDF Note 9234, Search for Heavy Top t →W q in lepton plus jets events, (2008). 190. P. Langacker, R. W. Robinett, J.L. Rosner, Phys. Rev. D30, 1470 (1984). 191. J.C. Pati and A. Salam, Phys. Rev. D10, 275 (1974); R.N. Mohapatra and J.C. Pati, Phys. Rev. D11, 566 (1975), 11, 2558 (1975); G. Senjanovic and R.N. Mohapatra, Phys. Rev. D12, 1502 (1975). 192. CDF Note 9160, High-mass di-electron resonance √ search in p? collisions at s = 1.96 TeV, (2008). p 193. CDF Collaboration, Phys. Rev. Lett. 96, 211801 (2006). 194. CDF Collaboration, Phys. Rev. Lett. 99, 171802 (2007). ′ 195. D? Note 4375, Search for heavy Z bosons in the dielectron channel with 200 pb?1 of data with the D? detector, (2004).

Review - Page 38
196. E. Eichten, K. Lane, J. Womersley, Phys. Lett. B405, 305 (1997). 197. D? Note 4561, Search for technicolor particles ρT and ωT in the dielectron channel with 200 pb?1 of data with the D? detector, (2004). ′ 198. D? Note 4577, Search for heavy Z bosons in the dimuon channel with 250 pb-1 of data with the D? detector, (2004). 199. B. Murakami, Phys. Rev. D65, 055003 (2002). 200. P. Langacker and J. Kang, Phys. Rev. D71, 035014 (2005). ? 201. D? Collaboration, Search for tt resonances in the p (s) = lepton+jets ?nal state in p? collisions at p 1.96 TeV, submitted to Phys. Lett. B, arXiv:hepex/0804.3664v1 (2008). ? 202. D? Note 5600, Search for tt resonances inp lepthe (s) = ton+jets ?nal state in p? collisions at p 1.96 TeV, (2008). 203. C.T. Hill and S. Parke, Phys. Rev. D49, 4454 (1994). ? 204. CDF Note 8087, Search for resonant tt production in p p? collisions at (s) = 1.96 TeV, (2008). p ? 205. CDF Note 8675, Limit on resonant tt production in p p? collisions at (s) = 1.96 TeV, (2008). p 206. CDF Collaboration, Phys. Rev. D75, 091101 (2007). 207. D? Collaboration, Phys. Rev. Lett. 100, 031804 (2008). 208. D? Collaboration, Phys. Lett. B641, 423 (2006). ′ 209. D? Collaboration, Search for W boson resonances decaying to a top quark and a bottom quark, accepted by Phys. Rev. Lett., arXiv:hepex/0803.3256v1 (2008). ′ 210. CDF Note 9150, W -like resonances in the t? decay b channel with 1.9 fb?1 , (2008). 211. N. Arkani-Hamed, S. Dimopoulos, G. Dvali, Phys. Lett. B429, 263 (1998). 212. D? Collaboration, Phys. Rev. Lett. 95, 091801 (2005). 213. CDF Collaboration, Phys. Rev. Lett. 99, 171801 (2007). 214. D? Collaboration, Phys. Rev. Lett. 100, 091802 (2008). 215. CDF Collaboration, Search for new heavy particles √ decaying to ZZ→eeee in p? collisions at p s = 1.96 TeV, submitted to Phys. Rev. D, arXiv:hepex/0801.1129v1 (2008). 216. G. Giudice, R. Rattazzi, J.D. Wells, Nucl. Phys. B544, 3 (1999). 217. D? Collaboration, Search for large extra √ dimensions in the mono-photon ?nal state at s = 1.96 TeV, submitted to Phys. Rev. Lett., arXiv:hepex/0803.2137v1 (2008). 218. CDF Collaboration, Phys. Rev. Lett. 97, 171802 (2006). 219. CDF Note 9308, Search for new physics in the exclusive jets/photon+MET channel in Run-II, (2008). 220. D? Note 4400, Search for large extra spatial dimensions in jets + missing ET topologies, (2004). 221. D? Collaboration, Search for large extra √ dimensions in the mono-photon ?nal state at s = 1.96 TeV, submitted to Phys. Rev. Lett., arXiv:hepex/0803.2137v1 (2008). 222. CDF Note XXXX, Search for anomalous diphoton+X production, (2007). / 223. CDF Note 9339, Search for anomalous γγ +ET events in 2 fb?1 of data, (2007).

Arnaud Duperrin

Review of Searches for Higgs Bosons and BSM Physics at the Tevatron - Page 39

224. CDF Collaboration, Phys. Rev. Lett. 97, 031801 (2006). 225. CDF Collaboration, Phys. Rev. D75, 112001 (2007). 226. CDF Note 9335, Search for new physics in lepton + photon + missing transverse energy + b-jets events ? and ttγ cross section measurement, (2008). 227. CDF Note 8452, Searching for the anomalous production of Z-Bosons with high transverse momentum in 0.94 fb?1 at the Tevatron, (2006). 228. CDF Collaboration, Phys. Rev. Lett. 89, 041802 (2002). 229. CDF preliminary result, Vista/Sleuth global search √ for new physics in 2 fb?1 of p? collisions at s = p 1.96 TeV (2008); see C. Henderson, for the CDF Collaboration, Contribution to the proceedings of the XLIIIth Rencontres de Moriond: QCD and High-Energy Interactions, arXiv:hep-ex/0805.0742v1 (2008). 230. CDF Collaboration, Model-independent global search for new high-pT physics at CDF, submitted to Phys. Rev. Lett., arXiv:hep-ex/0712.2534v1 (2007). 231. F. Maltoni and T. Stelzer, J. High Energy Phys. 0302, 027 (2003) 232. CDF Collaboration, Model-independent and quasimodel-independent search for new physics at CDF, submitted to Phys. Rev. D, arXiv:hepex/0712.1311v1 (2007).



学霸百科 | 新词新语

All rights reserved Powered by 甜梦文库 9512.net

copyright ©right 2010-2021。
甜梦文库内容来自网络,如有侵犯请联系客服。zhit325@126.com|网站地图