ATLAS PHYSICS STUDY in CHINA 南昌高能物理大会 – 2010.4.18 冯 存 峰 ( 山东大学 )

1. ATLAS PHYSICS STUDY in CHINA 南昌高能物理大会 – 2010.4.18 冯 存 峰 (山东大学) On behalf of Atlas Chinese Cluster (IHEP, Nanjing U., Shandong U., USTC)

2. Outline • Introduction • Standard model (electroweak) tests • Top physics • Higgs search and property • SUSY • Detector commissioning • Summary 2 Single top meetingFCPPL workshop, Wuhan

3. Introduction The LHC status Single top meetingFCPPL workshop, Wuhan

4. Physics is now at our door ! Single top meetingFCPPL workshop, Wuhan

5. WZ studies • WZ production can involve TGC and sensitive to new physics • First observed by CDF - PRL 98, 161801 (2007) • Little is known so far… First observation of WZ at CDF • cross section measurement with early ATLAS data • a precision electroweak test • assess systematic effects for multi-lepton analyses – crucial for H->ZZ … As early as when MET and multivariate techniques are not fully commissioned Apply basic cut based lepton identifications only. Single top meetingFCPPL workshop, Wuhan

6. CSC results of WZ analysis at ATLAS Single top meetingFCPPL workshop, Wuhan

7. Prospect for 1/fb: event yield, cross section precision a 10% measurement! large room for optimization 4-channel combination: uncertainty correlations accounted for. based on v14 MC samples Single top meetingFCPPL workshop, Wuhan

8. Ttbar cross section Ttbar Total:160pb Semi-lepton: 48pb Di-lepton: 8pb Single top meetingFCPPL workshop, Wuhan

9. Ttbar semi-lepton @10TeV (200pb-1) Event selection • Exactly one lepton (electron or muon) with pT> 20 GeV. • Missing ET > 20 GeV. • At least four jets with pT> 20 GeV. • at least three jets have pT> 40 GeV. No b-jet tag used ATL-PHYS-PUB-2009-087 Single top meetingFCPPL workshop, Wuhan

10. Ttbar semi-leptonic cross section Wm cut Cut and count Top mass fit Electron Mu Single top meetingFCPPL workshop, Wuhan

11. uncertainties systematic Single top meetingFCPPL workshop, Wuhan

12. ttbar spin correlation and W polarization Angle between t(t) and spin analysers Angle betweenspin analysers • tt spin correlation parameters with final objects 1, 2 spin analyzer qualities For V-A: (l+) =1, (b)=-0.41…. • W polarizationanalysis with final objects angle between lepton in W rest frame and W direction in top rest frame SM predictions for these parameters Single top meetingFCPPL workshop, Wuhan

13. Single lepton channel analysis -- high BR with moderate background -- in situ W and top mass(transverse) constraints W polarization: Preparing for summer CONF note SM predictions (730pb-1) (220pb-1) * *due to unknown discrepancy between fast and full simulation Single top meetingFCPPL workshop, Wuhan

14. Single Top Quark Production at LHC Wt t-channel s-channel σNLO~60 pb (7TeV) ~246 pb (14TeV) σNLO~3 pb (7TeV) ~11 pb (14TeV) σNLO~15 pb (7TeV) ~ 66 pb (14TeV) Single top production • Weak production mechanism: Wtb vertex • Signature: 1 central high-pt b-jet, W leptonic decay, 1-2 extra jets 14 Single top meetingFCPPL workshop, Wuhan

15. Single top t-channel Analysis (14TeV) S~4412 S/B=0.12 • Event Selection • harder b-jet cut: pT>50 GeV • forward light jet cut |η|>2.5 (cut based analysis only) • 1 BDT discriminant vs top pairs 1fb-1 BDT Cut 1fb-1 S~540 S/B=1.3 CSC note 15 Single top meetingFCPPL workshop, Wuhan

16. Top Yukawa coupling in ttH(HWW*) • 轻子和夸克通过与Higgs粒子的Yukawa耦合获得质量。 • 通过ttH过程研究top夸克的Yukawa耦合，可能是LHC唯一可测量的Yukawa耦合常数 gt -- Cross section measurement  coupling constant gt extraction Single top meetingFCPPL workshop, Wuhan

17. Signal & Background • Balance between statistic and s/b, only study: • 2 same change lepton channel, & • 3 lepton channel b • Signal 1：ttH2b4j2l2Vl 6jets + 2 same charge lep. + MissEt Possible BGs: tt(1l), tt(2l), ttZ, ttW, tttt, ttWW, ttbb... • Signal 2：ttH2b2j3l3Vl 4jets + 3leptons + MissEt Possible BGs: tt(2l),ttZ,ttW,tttt,ttWW,ttbb Lepton Isolation is crucial P 2 leptons 4 light jets P b b P 3 leptons 2 light jets P b Single top meetingFCPPL workshop, Wuhan

18. Isolation in Calorimeter and tracker • Calorimeter Isolation: • The total energy deposited in the calorimeter around the lepton in a cone size of 0.2 should smaller than 10GeV • Tracker Isolation: • The maximum pt of extra tracks in ID around the lepton in a cone size of 0.2 should smaller than 2 GeV Isolated lepton Uniso. lepton Lepton Calo track Calorimeter Cone size 0.2 Clusters around the lepton Inner detector Tracks around the lepton Electron Muon Single top meetingFCPPL workshop, Wuhan

19. Combined systematic uncertainties Take 10% Take 10% Single top meetingFCPPL workshop, Wuhan

20. Expectec direct measurement results precision(160GeV): 2L : 69% 3L : 66% Combined: 47% Result uncertainties dominated by Background systematic uncertainty, to estimate and correct it by a real data driven method is essential ! Single top meetingFCPPL workshop, Wuhan

21. WH coupling in: WH(H->WW*) @ 30 inverse fb , accepted in ATLAS CSC-NOTE WH coupling measurement needs more work to improve Apr 2, 2008 Lian-You SHAN, CACC7 21 Single top meetingFCPPL workshop, Wuhan

22. Single top meetingFCPPL workshop, Wuhan

23. γ Trigger Efficiency plot with 10pb-1 g20_loose trigger near 100% for pT>25GeV Work in progress This plot is using γ+jet events, which corresponding to 10 pb-1. It is possible to implement these methods with low statistic. Single top meetingFCPPL workshop, Wuhan

24. 寻找R宇称破坏的e超对称粒子 Single top meetingFCPPL workshop, Wuhan

25. Expected Limits@1/fb （preparing for summer CONF note） @ @ @ @ @ @ @ @ M = 100 GeV M = 125 GeV ATLAS: D0: M = 175 GeV M = 150 GeV ATLAS: 在1fb-1相同亮度下，ATLAS对R宇称破缺参数灵敏度预期，好于现有D0实验测量 PRL 100, 241803 (2008)近一个量级 D0: Single top meetingFCPPL workshop, Wuhan

26. Single top meetingFCPPL workshop, Wuhan

27. From D. Liu@SDU Single top meetingFCPPL workshop, Wuhan

28. b-jet tag B Tagging Efficiency Light Jet Mistag Rate Tag. eff. & Mistag on going J. Yu@NJU ,Y. Bai@IHEP J. Wang@SDU B Jet Identification B Tagging Efficiency B Tagging Efficiency Light Jet Mistag Rate W+jets events QCD events W+jets events QCD events Single top meetingFCPPL workshop, Wuhan

29. Jet Direction Tracks • Decay Length Significance: • Performance studies • Correlation between Btag estimator studies • Miss-tag rate estimate from data • Discrimination Power: • Heavy Flavor Jet: tend to be positive • Light Flavor Jet: presence of a secondary vertex (resolution effect of light jet) • In parallel, tracking DPD maker validation (on data) Secondary Vertex Primary Vertex SV0 b tag studies Bai Yu @IHEP Single top meetingFCPPL workshop, Wuhan

30. Summary • LHC and ATLAS is almost ready for physics now, need more performance study • Many works done • Hardware, Detector commissioning, Computing facility • MC study • Few conf notes are preparing • Many subjects are in exploration • Many challenges ahead • Your suggestion are welcome. Looking forward to exciting physics! Single top meetingFCPPL workshop, Wuhan

31. ATLAS中国组欢迎你的建议和帮助！ 谢谢！ Single top meetingFCPPL workshop, Wuhan

32. backup Single top meetingFCPPL workshop, Wuhan

33. (Di-)Boson • Electroweak boson production at LHC • From Standard Candle to Physics • ATLAS electron identification W,Z WW For each 100pb-1 , 1M W->eν, 200 pure leptonic WW! (7 TeV PP) concentrate on ee channel now. From Y. Liu@USTC Single top meetingFCPPL workshop, Wuhan

34. WW CERN-OPEN-2008-020 Higgs, of course! gg->H->WW • Two isolated leptons, pT>20 GeV, |η|<2.5 • Veto events with a jet of pT>20 GeV, |η|<3. • MET > 50 GeV • Veto on events with a Z peak. • Angular cuts among leptons and MET • (different for WW cross section measurement and anomalous coupling sensitivity) . Need re-optimize for 7 TeV 200 pure leptonic WW events in each 100pb-1 Single top meetingFCPPL workshop, Wuhan

35. Z+γ production on going: (σ (zγμμγ)=1.4pb @10TeV) SM forbidden From M. liu@USTC Single top meetingFCPPL workshop, Wuhan