DO, présenté par F. Badaud, à paraître dans les Proceedings (World Scientific)The results for searches for Supersymmetry by the CDF and D0 collaborations in ppbar collisions at √s = 1.96 TeV are presented here. Searches for chargino/neutralino and the lightest stop, as well as scenarios with R-parity violation are focused here. The integrated luminosity analyzed ranges from 300 to 800 pb-1 depending on the search. Further informations can be found on the public web pages of the two experiments

Badaud, F.

HAL Clermont Université

Supersymmetry results at the TevatronF. BadaudTo cite this version:F. Badaud. Supersymmetry results at the Tevatron. DIS2006 XIV International Workshop onDeep Inelastic Scattering, Apr 2006, Tsukuba, Japan. 2006. <in2p3-00104934>HAL Id: in2p3-00104934http://hal.in2p3.fr/in2p3-00104934Submitted on 9 Oct 2006HAL is a multi-disciplinary open accessarchive for the deposit and dissemination of sci-entific research documents, whether they are pub-lished or not. The documents may come fromteaching and research institutions in France orabroad, or from public or private research centers.L’archive ouverte pluridisciplinaire HAL, estdestine´e au de´poˆt et a` la diffusion de documentsscientifiques de niveau recherche, publie´s ou non,e´manant des e´tablissements d’enseignement et derecherche franc¸ais ou e´trangers, des laboratoirespublics ou prive´s.July 2, 2006 10:44 Proceedings Trim Size: 9in x 6in testSUPERSYMMETRY RESULTS AT THE TEVATRONFRE´DE´RIQUE BADAUDon behalf of the CDF and D∅ collaborationsLaboratoire de Physique Corpusculaire-IN2P3/CNRS, Clermont-Ferrand, FranceE-mail: badaud@clermont.in2p3.frThe results for searches for Supersymmetry by the CDF and D∅ collaborations inpp¯ collisions at√s = 1.96 TeV are presented here. Searches for chargino/neutralinoand the lightest stop, as well as scenarios with R-parity violation are focused here.The integrated luminosity analyzed ranges from 300 to 800 pb−1 depending onthe search. Further informations can be found on the public web pages of the twoexperiments 1’ 2.1. SupersymmetrySupersymmetry (SUSY) predicts the existence of a new particle for eachof the Standard Model (SM) particles, differing by half a unit in spin butotherwise sharing same quantum numbers. A discrete multiplicative sym-metry, called R-parity, is defined as Rp = (−1)(2S+3B+L) where B is thebaryon number, L is the lepton number and S is the spin of the particle,such that a SM particle carries Rp = +1 and a SUSY particle Rp = −1.Supersymmetric particles have not been observed yet implying that SUSYis a broken symmetry. In Rp conserving models, supersymmetric particlesare produced in pair and the lightest supersymetric particle (LSP) is stable.The masses for the proposed superpartners are potentially accessible at theTevatron.2. Charginos and neutralinos2.1. Multilepton final stateIn the mSUGRA scenario the superparticles are produced in pairs andthe lighter charginos and neutralinos, mixed state of electroweak gauginosand higgsinos, and the sleptons, are less massive than gluinos and squarks.The LSP is the χ˜01. In the case where charginos and neutralinos decayleptonically, χ˜±1 → `±ν`χ˜01 and χ˜02 → `±`∓χ˜01, very clean final states of1July 2, 2006 10:44 Proceedings Trim Size: 9in x 6in test2three leptons plus missing energy ( /ET) caused by the χ˜01’s and the neutrinoare expected. Very few SM processes contribute to such a signature, thedominant being Drell-Yan plus a misidentified jet or a γ → e+e− conversion,and real WZ production. New CDF results on trileptons are summarizedin Table 1. No significant excess is observed. A previous D∅ analysis sets alimit of 117 GeV/c2 on the χ˜±1 mass considering a mSUGRA scenario withsleptons slightly heavier than the χ˜±1 and no sleptons mixing.Table 1. CDF results of search for χ˜±1χ˜02→ `±`∓ + X. LS means Like Sign.Channel µµ + ` µe + ` LS ee LS µµ LS µeLuminosity 745 pb−1 700 pb−1 704 pb−1 704 pb−1 704 pb−1SM expectation 0.64 ±0.18 0.78 ±0.11 2.6 ±0.4 3.5±0.6 0.7 ±0.1observed 1 0 4 5 02.2. DiphotonsIn another SUSY model, Gauge Mediated Supersymmetry Breaking(GMSB), the LSP is the gravitino, the super partner of the graviton. Eachof the χ˜01’s from chargino-neutralino production will decay into a gravitinoand a photon. The signal is a final state with two energetic photons andlarge /ET. The physical backgrounds are estimated negligible. Instrumentalbackgrounds come from QCD processes with either real γ or jets misiden-tified as γ and W (→ eν)γ and W (→ eν)jet production where the electronand the jet are misidentified as a photon. D∅ has searched for this signaturein 760 pb−1 of data. 2 events are observed with an expected backgroundof 2.1 ± 0.7 events. An upper limit, see Figure 1, is set on GMSB SUSYproduction.3. Squarks and gluinos3.1. StopsIn many scenarios, the lightest stop quark, t˜1, is expected to be the lightestof all the squarks. Due to their strong couplings, squarks and gluinos areexpected to be produced abundantly at hadron colliders. D∅ has looked forfinal states e±µ∓ + bb¯+ /ET and µ±µ∓ + bb¯+ /ET, which is the signature oft˜1 pair production, followed by t˜1 → b`ν˜, which is expected to be the dom-inant decay mode when mν˜ ≈ mW . For the eµ final state, two regions of∆M = mt˜1 −mν˜ are examined. The expected number of total backgroundJuly 2, 2006 10:44 Proceedings Trim Size: 9in x 6in test3is 23.0±3.1 (40.7±4.4) for 21(42) observed in the eµ low ∆m (high ∆m) re-gion. In the µµ final state the expectation from SM is 2.88±0.43+0.10−0.04 while1 event is observed. All the results are compatible with SM expectations.The regions for which the calculated cross section upper limit is smallerthan the theoritical cross section are 95% C.L. excluded and are shown inFigure 2.4. R-parity violationCDF looked for Rp violating SUSY in the multilepton channel. The searchis performed under the assumption that SUSY particles are pair producedand decay under Rp conservation while only the LSP can decay into twocharged leptons plus a neutrino via the λ121 or λ122 coupling. Both the3 and 4 leptons signatures, ee`(`) and µµ`(`) with ` = e orµ, were in-vestigated and the observation is compatible with the expectation. As anexample, Figure 4 shows the invariant mass distribution of the leading lep-tons. The channels are combined and upper limits at 95% C.L. on thecross sections, σ < 0.21 pb for λ121 > 0 and σ < 0.11 pb for λ122 > 0, areobtained.4.1. Long-lived LSPD∅ looked for the decay of the neutralino to leptons and a neutrino in 383pb−1 of data. The analysis focuses on the scenario where the Rp couplingis weak and the LSP would travel ≥ 5 cm before decaying. This possibilitywas inspired by an excess in dimuon events reported by NuteV. No eventsare observed with an expectation of 0.8± 1.1± 1.1 from backgrounds andthe limit set excludes the possibility that the NuteV events are due toneutralino decay.5. ConclusionsCDF and D∅ have searched for SUSY and no deviation from the StandardModel have been found. SUSY parameter regions have been excluded. Highluminosity samples, corresponding to 1 fb−1 are being analyzed.References1. http://www-cdf.fnal.gov/physics/exotic/exotic.html2. http://www-d0.fnal.gov/Run2Physics/WWW/results/np.htmJuly 2, 2006 10:44 Proceedings Trim Size: 9in x 6in test4Figure 1. 95% C.L. limit on GMSB SUSYSnowmass Slope obtained in the analysis(thick blue line) and in the previous D∅result (dot-dashed) purple-line. SUSY LO(NLO) cross-section is shown in black solid(dashed) line.Figure 2. 95% C.L. excluded region in thestop search for the combination of eµ andµµ final state.Figure 3. The red curve is the 95% C.L.limit on pair production of neutral, long-lived particles.)2Invariant Mass of 1st & 2nd Leptons (GeV/c40 50 60 70 80 90 100 110 120 1302Events / 8 GeV/c024681012-1CDF Run II Preliminary, 346 pb2Events / 8 GeV/cDataγDY + Mis-ID Jetst-tbarDiboson)121λRpV SUSY (2 = 99.4 GeV/c01χMFigure 4. Search for Rp violating SUSYin the multilepton channel. Invariant massdistribution of the leading leptons.

Supersymmetry results at the Tevatron

Abstract

Similar works

Full text

Available Versions

HAL Clermont Université

HAL-IN2P3