1 / 37

Giulia Manca (University of Liverpool) On behalf of the CDF collaboration

Search for Squark and Gluino Production In Missing Energy+Jets at CDF. Giulia Manca (University of Liverpool) On behalf of the CDF collaboration. SUSY05, Durham (UK) 18-23 July 2005. Outline. 2. CDF and the Tevatron Theory and Motivation Analysis strategy Kinematic selection Results

brinly
Télécharger la présentation

Giulia Manca (University of Liverpool) On behalf of the CDF collaboration

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Search for Squark and Gluino Production In Missing Energy+Jets at CDF Giulia Manca (University of Liverpool) On behalf of the CDF collaboration SUSY05, Durham (UK) 18-23 July 2005

  2. Outline 2 • CDF and the Tevatron • Theory and Motivation • Analysis strategy • Kinematic selection • Results • Conclusions and Outlook G. Manca (U.Liverpool) SUSY05, Durham (UK), 20 July 2005

  3. design goal Still long way to go! base goal Mar ‘01-Feb ‘04 ~254 pb-1 CDF and the Tevatron • High Luminosity • Tevatron 1 fb-1! • CDF running at high efficiency p p at ECM 1.96 TeV G. Manca (U.Liverpool) SUSY05, Durham (UK), 20 July 2005

  4. g ~ G c c0 c0 Benchmark: mSugra: c01 LSP, stable (parameters: M0,M1/2,tanb,A0,m) Supersymmetry New (broken) Symmetry relating Fermions & Bosons G +1 (SM particles) R-Parity Quantum Number-> -1 (Susy particles) G. Manca (U.Liverpool) SUSY05, Durham (UK), 20 July 2005

  5. Missing Transverse Energy Jets 103 s (pb) Missing Transverse Energy 1 10-3 10-6 10-9 Phys.Rev.D59:074024,1999 300 500 700 Squark and Gluino at the Tevatron PRODUCTION: DECAY: -Produced by strong interaction -Heavy! -Signature:>2 jets + +Large Missing Transverse Energy (MET) + Large Total Transverse Energy Large HT = Sjets(EjetsT) G. Manca (U.Liverpool) SUSY05, Durham (UK), 20 July 2005

  6. ~ ~ ~ ~ ~ ~ Current limits Present best limits: • LEP II (indirect) • D0 Run II (see talk from D.Sojot on Friday) • For mSugra: tanb=3, A0=0,m<0, q=u,d,c,s,b: • 4j(gg) :M0=500 GeV-> M(g) >233 GeV/c2 • 3j(gq) :M(g)=M(q) -> M(q) >333 GeV/c2 • 2j(qq) :M0=25 GeV -> M(q) >318 GeV/c2 ~~ ~ ~ ~ ~ ~~ G. Manca (U.Liverpool) SUSY05, Durham (UK), 20 July 2005

  7. s46 s41 s35 Reference SUSY points • Chosen region not excluded by other experiments • Simulated several mSUGRA points in M0-M1/2 with A0=0, sign(m)=-1, tanb=5 and third generation removed from 2  2 process (Isajet) • Chosen 3 points to optimise the analysis selection criteria GeV/c2 ~ ~ ~ G. Manca (U.Liverpool) SUSY05, Durham (UK), 20 July 2005

  8. Analysis Strategy COUNTING EXPERIMENT • Optimise selection criteria for best signal/background value; • Apply selection criteria to the data • Define the signal region and keep it blind • Test agreement observed vs. expected number of events in orthogonal regions (“control regions”) • Look in the signal region and count number of SUSY events !! • Or set limit on the model G. Manca (U.Liverpool) SUSY05, Durham (UK), 20 July 2005

  9. Trigger and Event pre-Selection • Trigger on Missing Transverse Energy>35 GeV + 2 jets (ET>10 GeV) • Apply “Basic Cuts” to clean up the sample and eliminate effects MC does not reproduce • beam losses • cosmic and beam halo muons • detector failures (hot/dead towers, poorly instrumented regions,…) G. Manca (U.Liverpool) SUSY05, Durham (UK), 20 July 2005

  10. Backgrounds +SUSY • Several SM processes can give jets with missing energy: • Z nn + 3 jets • Wn + 2/3 jets • Top-antitop • Z + 2/3 jets • WW • Hadron jets (“QCD” events) [1] Cacciari et. al., JHEP 404, 68(2004) G. Manca (U.Liverpool) SUSY05, Durham (UK), 20 July 2005

  11. Hadron Jets Background • Selected regiondominated by Jet events in the data satisfying the pre-selection criteria • Compared distributions MC events to data and obtained scale factor to the MC ~1.0 CDF Run II preliminary CDF Run II preliminary Fit: 1.02  0.01 G. Manca (U.Liverpool) SUSY05, Durham (UK), 20 July 2005

  12. Analysis Event selection Selection criteria optimised using S/B To reject QCD To reject electrons Signal region Using these selection criteria: (254pb-1) G. Manca (U.Liverpool) SUSY05, Durham (UK), 20 July 2005

  13. S/B SUSY Monte Carlo Different mSUGRA parameter values have been studied: number of flavours, tanb and sign of mfor the same value of M0-M1/2. CDF Run II CDF Run I and D0 Run II generations CDF Run I changing sign m No large difference observed over all scenarios-> small model dependency G. Manca (U.Liverpool) SUSY05, Durham (UK), 20 July 2005

  14. Control Regions • Several regions different from the signal region (“control regions”) examined to verify the robustness of the Monte Carlo predictions: analysed two: CR1: Veto electron (EM fraction < 0.9) -> QCD dominated Hadron jets: 165  6 EW: 36  2 Tot Expected: 201  6 Observed: 183  14 CR1 & CR2 Signal Region Only statistical uncertainty CR2: Require EM fraction > 0.9 -> EW and QCD similar Hadron Jets: 16  1 EW : 12  1 Tot Expected:281 Observed: 235 CDF Run II preliminary 254 pb-1 CDF Run II preliminary, 254 pb-1 Good agreement Data-MC CR1 CR1 G. Manca (U.Liverpool) SUSY05, Durham (UK), 20 July 2005

  15. Systematic Uncertainties G. Manca (U.Liverpool) SUSY05, Durham (UK), 20 July 2005

  16. Looking at the Signal Region • In L = 254 pb-1 : • SM Expected Events = 4.1  1.5 • Observed Events = 3 HT distribution after applying all the cuts except HT >350 GeV MET distribution after applying all the cuts except MET >165 GeV G. Manca (U.Liverpool) SUSY05, Durham (UK), 20 July 2005

  17. Event 1 HT = ET(1st) + ET(2nd) + ET(3rd) = 404 GeV ET(1st) = 172 GeV ET(2nd) = 153 GeV ET(4th) = 65 GeV ET (3rd) = 80 GeV Missing ET = 223.3 GeV G. Manca (U.Liverpool) SUSY05, Durham (UK), 20 July 2005

  18. Conclusions and Outlook • Performed blind search for squark and gluinos over 254 pb-1 CDF RUN II data • Selection criteria have been optimised for several mSugra scenarios: • Find relatively small dependence on tanb, sign of m and and number of flavours • Demonstrated good understanding of data and SM backgrounds in “control regions” • No evidence for Squarks and Gluinos • Data agree with background estimate • Full interpretation in progress • Future improvements with increased luminosity G. Manca (U.Liverpool) SUSY05, Durham (UK), 20 July 2005

  19. BACK-UP SLIDES G. Manca (U.Liverpool) SUSY05, Durham (UK), 20 July 2005

  20. The CDF-II detector polar angle  Silicon Tracking Detectors Central Drift Chambers (COT) h = 1.0 Solenoid Coil h = 2.0 EM Calorimeter  h = 2.8 Hadronic Calorimeter Muon Drift Chambers Muon Scintillator Counters Steel Shielding G. Manca (U.Liverpool) SUSY05, Durham (UK), 20 July 2005

  21. The CDF-II detector Calorimeter simulation: GFLASH for showering COT Muon Chambers Plug Calorimeter Silicon G. Manca (U.Liverpool) SUSY05, Durham (UK), 20 July 2005

  22. Beam Background Cuts Sjets(EjetT x f jetEMC) EEMF = > 0.15 Sjets(EjetsT) Stracks(PtrackT) ECHF =1/NjetsxSjets >0.15 EjetT Only for central (|eta| < 1.1) jets G. Manca (U.Liverpool) SUSY05, Durham (UK), 20 July 2005

  23. Criteria to select QCD region in data In JET20 data: • Basic cuts • Et(j1)>90 GeV, Et(j2)>60 GeV • MEt Significance=MEt/Smet towers<3.5 GeV-1/2 • Et(j1)+Et(j2)+Met<100 GeV G. Manca (U.Liverpool) SUSY05, Durham (UK), 20 July 2005

  24. After Basic Cuts G. Manca (U.Liverpool) SUSY05, Durham (UK), 20 July 2005

  25. Delta Phi Optimisation G. Manca (U.Liverpool) SUSY05, Durham (UK), 20 July 2005

  26. Control Regions I CR0: QCD dominated -Basic cuts - ET of the jets - EMF of the jets - Out of the BB QCD: 3421 EW: 144 SM Expected: 3564  54 Observed: 4438  67 • Three regions orthogonal to the signal region (“Control regions”) examined to verify the robustness of the Monte Carlo predictions CR1 & CR2 Blind Box CR0 CR1: QCD dominated - Basic cuts - ET of the jets - EMF of the jets - 120<MET<165 - 280<HT<350 GeV SM Expected: 201  7 Observed: 183  14 Only statistical uncertainty CR2 (EM dominated): - Basic cuts - ET of the jets - At least one jet with EMF>0.9 - 120<MET<165, 280<HT<350 GeV SM Expected: 27  0 Observed: 23  5 G. Manca (U.Liverpool) SUSY05, Durham (UK), 20 July 2005

  27. Efficiency of the signal points Using these selection criteria: G. Manca (U.Liverpool) SUSY05, Durham (UK), 20 July 2005

  28. Jet Energy Scale at CDF • A Jet = energy deposited in the hadronic calorimeter in a cone of R=0.7(this analysis) • An Energy Correction is necessary to scale the measured energy back to the energy of the final state particle level jet (due to several effects as non-linearity of the calorimeter or un-instrumented regions of the detector) • The factor we apply accounts for all these effects, using different methods; e.g. balancing g-jet Pt of the g-jet system: Before relative corrections After corrections • DATA • Pythia • Herwig G. Manca (U.Liverpool) SUSY05, Durham (UK), 20 July 2005

  29. Different effects that can distort the measured Jet energy G. Manca (U.Liverpool) SUSY05, Durham (UK), 20 July 2005

  30. Relative Scale G. Manca (U.Liverpool) SUSY05, Durham (UK), 20 July 2005

  31. Multiple Interactions Correction G. Manca (U.Liverpool) SUSY05, Durham (UK), 20 July 2005

  32. Underlying Event G. Manca (U.Liverpool) SUSY05, Durham (UK), 20 July 2005

  33. Out-of-cone corrections G. Manca (U.Liverpool) SUSY05, Durham (UK), 20 July 2005

  34. Total correction G. Manca (U.Liverpool) SUSY05, Durham (UK), 20 July 2005

  35. Absolute Correction G. Manca (U.Liverpool) SUSY05, Durham (UK), 20 July 2005

  36. The Events • In L = 254 pb-1 : • SM Expected Events = 4.1  1.5 • Observed Events = 3 G. Manca (U.Liverpool) SUSY05, Durham (UK), 20 July 2005

  37. Cross sections • mSugra: squarks 1,2nd family • nearly degenerate and heavier than sleptons • cannot be lighter than 0.8*M(gluino) G. Manca (U.Liverpool) SUSY05, Durham (UK), 20 July 2005

More Related