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tW 共振态 b *在 LHC/CMS 上的寻找

tW 共振态 b *在 LHC/CMS 上的寻找. 孟祥伟 Guoming Chen, Xiangwei Meng , Sarmad Shaheen, Huaqiao Zhang and Shihai Zhu IHEP,CAS 粒子天体中心 . 高能物理研究所 中国科学院. 中国物理学会高能物理分会 第 9 届全国会员代表大会暨学术年会 武汉 . 湖北 4 月 18-22 日 .2014 年. Contents. Introduction Data Strategy and methods preSelection

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tW 共振态 b *在 LHC/CMS 上的寻找

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  1. tW共振态b*在LHC/CMS上的寻找 孟祥伟 Guoming Chen, Xiangwei Meng, Sarmad Shaheen, Huaqiao Zhang and Shihai ZhuIHEP,CAS 粒子天体中心.高能物理研究所 中国科学院 中国物理学会高能物理分会 第9届全国会员代表大会暨学术年会 武汉.湖北 4月18-22日.2014年 第9届全国会员代表大会暨学术年会 20,04, 2014

  2. Contents • Introduction • Data • Strategyand methods • preSelection • Background estimation • Selection optimization • Systematic uncertainties • Limit setting • Search results • Summary 第9届全国会员代表大会暨学术年会 20,04, 2014

  3. Introduction • Single top quark signature sensitive to many models of new physics • b* framework • Excite quark/lepton could reveal thesubstructure of SM fundamentalparticles • Composite 3rd generation quarkmodel allows FCNC/SM coupling • Previous searches mostly exploit the coupling between excited and u/d • Recent search by ATLAS using full 7 TeV data, set lower limit to ~1TeVwith4.7/fb Phys. Lett. B 721 (2013) 171-189 • Aimatfull 8TeV2012 dataatCMS • Sharingthesame selection and backgroundmodeling as other tW analysis 第9届全国会员代表大会暨学术年会 20,04, 2014

  4. Single b* theory • b*predicted by composite 3’rd generation model J. Nutter, R. Schwienhorst, D. Walker, J.-H. Yu, Phys. Rev. D 86 (2012) 094006,arXiv:1207.5179 [hep-ph] • generated coupling to a gloun and a b quark • decay could be bg, bZ, bH or tW • purely left-handed, purely right-handed, orvector like with equal couplings to both left and right-handed parts Leading-order Feynman diagram for single-b∗-quark production and decay toWt 第9届全国会员代表大会暨学术年会 20,04, 2014

  5. Data and MC samples • 2012 data: 8TeV 19.8/fb Muon/Electron data Stream • MC samples • b* samples MadGraph5+pythia • Other backgrounds: official production • Dedicated b*tWlepton+jet, left-/right-handed b* full simulation, central produced 第9届全国会员代表大会暨学术年会 20,04, 2014

  6. Object definition/Event Selection CMS Single Top Group definition • Electron • MVA Id, Pt>30GeV, |eta| < 2.4 && not in 1.4442<|eta|<1.5660, leptonsRhoCorrectedRelIso<0.1 • Muon • PF/global Muon, Pt>26GeV,|eta|<2.1 leptonDeltaCorrectedRelIso<0.1 Delta R(muon,jet)>0.3 • Jet: PF AK5 jets, Pt>40 GeV, • B-tagged Jet: CSVT jets • MET: unclustered MET • Preselection • high Pt trigger Chain • Muon: HLT_IsoMu24_eta2p1_v13/ HLT_Ele27_WP80_v* • Primary vertex, Good Run, data cleaning etc. • Exactly one electron or muon: Veto additional loose leptons • Selectonly3 Jets, one b-tagged • Optimized with central jets of |eta|<2.4 • Preselection + lepton Pt>130 GeV 第9届全国会员代表大会暨学术年会 20,04, 2014

  7. QCD enriched control region Muon Channel Electron Channel • QCD from these plots are demonstrate only • from MC simulation predictions, limited by MC statistics • Anti-isolation control region: QCD purity ~99% • Electron: RhoCorrectedRelIso > 0.3 • Muon: DeltaCorrectedRelIso > 0.3 第9届全国会员代表大会暨学术年会 20,04, 2014

  8. QCD background Fitting • Fit methods: p0*MC + p1*QCD, • MC: MC simulation of single top, ttbar, W, Z, diboson • QCD: data QCD enriched control region Muon Channel QCD = 2227 ElectronChannel QCD = 3143 • QCD Data Driven Weight • Muon+3J1T : (2227 ± 240) / 33731 • Electron+3J1T: (3143 ± 298) / 46291 region contaminated foruncertainties Muon+3J1T : ± 130 / 33731 Electron+3J1T: ± 53 / 46291 第9届全国会员代表大会暨学术年会 20,04, 2014

  9. Data Driven W+Jets estimation • Fit methods: p0*MC + p1*Wjets + QCD • QCD: from Data • W+Jets: MC sample • MC: MC samples of single top, ttbar, Z, diboson Muon Channel W+jets = 8724 Electron Channel W+jets = 9211 • W+Jets Data Driven Weight • Muon+3J1T : (8724 ± 545) / 4598 • Electron+3J1T : (9211 ± 478) / 3956 MC to model the shape of W+jets, other detector systematics like JES/JER/Btag/mis-Tag/leptonSF etc also considered as the uncertainties that impact W+jets shape modeling 第9届全国会员代表大会暨学术年会 20,04, 2014

  10. Data driven Estimation Check For QCD estimation, we use W+jets from MC prediction Now fixed this W+jets to data driven value and redo QCD estimation as cross check Muon Channel QCD = 3304 Electron Channel QCD = 2299 Changes on QCD estimation within the fitting uncertainties Scale factors on other MCs are very close to 1 第9届全国会员代表大会暨学术年会 20,04, 2014

  11. Selection Optimization • Methodology • Optimize the cuts on jet pT, leading jet pT, MET, transverse W mass and MET • Change cut on jet pT, redo the whole analysis to find the best EXPECTED limit on the 1300 GeV b* • Fix jet pT to the value that find above, redo step1 with other variables and fix to the optimized cut • After optimized on all variables, loop again to the first optimized variable and so, until the optimization does not change the cut • This lead to the final selection • Preselection (jet |eta|<2.4) + lepton Pt > 130 GeV 第9届全国会员代表大会暨学术年会 20,04, 2014

  12. Events Yield Statistical uncertainties only 第9届全国会员代表大会暨学术年会 20,04, 2014

  13. Data/MC at final Selection MET Electron Channel Muon Channel 第9届全国会员代表大会暨学术年会 20,04, 2014

  14. Systematic Uncertainties I • Theory modeling (both Acceptance and Shape) • Q2: Dedicated samples with Factorization and Renormalization scale vitiate a factor 4 or ¼ 6-8% impact on the acceptance • Top Mass: Dedicated sample with top mass variant +-1 GeV 2-4% impact on the acceptance • Matching: Dedicated sample with MLE matching threshold changed 13% on ttbar • PDF: Use CT10 Error PDF to evaluate both acceptance and shape unc. 4-12%, on the backgrounds, 17-58% on the signal • Bkg Normalization • Acceptance only 第9届全国会员代表大会暨学术年会 20,04, 2014

  15. Systematic Uncertainties II following recipes from Top group recommendation, including both acceptance and shape uncertainties • Detector effects • Lepton Scale factors • ID/Trigger/Isolation • B-tagging • Mis-tagging • JES/JER • Pile-Up • Luminosity: 2.6%, Acceptance only • Theory modeling • Theory: >~10% • Bkg Normalization • ~10%-30% • Detector effects • JES: 1-5% • B-tag: 2-4% • Others: <1% • Luminosity: 2.6% 第9届全国会员代表大会暨学术年会 20,04, 2014

  16. Limit Setting • Tool: Theta • Method: Asymptotic CLs limits • Cross-checked by Bayesian limits within Theta • Likelihood function 第9届全国会员代表大会暨学术年会 20,04, 2014

  17. Fitting variable: b* mass b* mass Electron channel Muon channel 第9届全国会员代表大会暨学术年会 20,04, 2014

  18. Limit results Left-handed right-handed With Linear assumption for the theory cross-section Vector Like Exp: Obv: 第9届全国会员代表大会暨学术年会 20,04, 2014

  19. Systematics Impact on limit • Remove one systematic each time to see the change of expected limits • Biggest impact comes from PDF (11GeV) , all background normalization(7GeV), JES(4GeV) 第9届全国会员代表大会暨学术年会 20,04, 2014

  20. Summary and Outlook • b* searched on full 8 TeV data CMS with tW Lepton+Jetschannel • Data driven QCD and W+Jets estimation • Systematic uncertainties • No tW resonance bump found, Limit setting for left-,right-handed and vector like b* • b* below 950GeV excluded at 95% CL (purely left-handed couplings) • the systematics impact checked • Will combine results from dilepton channel and full hadronic channel 第9届全国会员代表大会暨学术年会 20,04, 2014

  21. THANKS! 第9届全国会员代表大会暨学术年会 20,04, 2014

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