模拟重建和分析

1、CMS Bc 模拟重建和分析 陈 国 明CMS ExperimentCMS2007年夏Large Hadron Collider23 inelastic events per bunch crossPile UpAt 1034Minimum bias eventsCMS ExperimentCMS ExperimentCross-sectional view of CMS =2.5zyxTransverse slice through CMS detectorClick on a particle type to visualise that particle in CMSPress “esc

2、ape” to exitATLAS取得了入场券 我国在硬件上的投了资, 取得了数据分析的入场券。 与投资多的国家有平等的机会，分析所有数据。数据分析是挑战 数据量大 本底高 探测器庞大, 软件环境复杂 竞争激烈：30 多个国家，200多个大学和研究所， 2000多科学家国内LHC物理分析的现状 从2000年开始连续3次向基金委申请面上项目, 用作CMS 的MC 研究, 未批准. 2004年设立重点基金, 并批准135万支持CMS和ATLAS的MC模拟. 20052008 4年 CMS 高能所 30 万 Bc HVV CMS 北大 35 万 大横动量J/ ATLAS 高能所 30 万 Htt A

3、TLAS 山大 30 万 tt 公用 10 万计算设施初步计划在高能所为CMS 和 ATLAS各建一个Tier2计算设施， 需经费 2000万 但还没有落实IHEP CMS物理分析设想 选取选取 2l+X sample 头三年头三年, 亮度亮度10103333, , 轻子触发横动量轻子触发横动量: : single electron 29GeV double electron 17GeV single muon 19GeV double muon 7GeV 合计合计 事例率事例率: 60Hz: 60Hz 每年每年: RECO 75TB, AOD 25TB, : RECO 75TB, AOD 2

4、5TB, 共共100TB100TB往后,亮度亮度10103434 , ,轻子触发横动量提高轻子触发横动量提高刻度 根据人力情况选做部分子探测器的刻度: MUCH +- 对, J/, Z0 峰, MUCH 径迹与TRACKER径迹的对比 TRACKER e+e-对, +-对, J/, Z0 峰, MUCH 径迹与TRACKER径迹的对比 ECAL e+e-对, J/, Z0 峰, 能量动量对比 亮度测量通过Drell-Yan e+e-,+- 的角分布测量亮度 目前，理论计算的误差 2%物理研究J/+-,+- 横动量分布BcJ/l, J/ J/+- ,e+e- Blind search e+e-

5、, +- , e+ - , e- + 共振态Stau 寻找HWW coupling l+l+ missing ETl-l- , l+l+ , without missing ET majorana Higgs search H ZZ l+l- jjCMS Bc goals and channels1. BcJ/l(J/l+l-) 2. BcJ/(J/l+ l-)Mass , life time and relative branching ratioBc Meson (Experiment)Experimental observation (CDF & D0 , Tevatron)Recent

6、 results on Bc meson199820042005Production of Bc at LHCCMS ExperimentAdavantage LHC : PP Energy 14TeV The production cross section of Bc meson will be 10 bigger than that at Tevatron. The CMS detector has the similar structure as CDF, and has larger detector cover region than CDF. CMS :eta(-2.5,2.5)

7、 CDF:eta(-1,1) (RUN I) eta(-1.5,1.5) (RUN II) (Muon system) The CMS detector has a better identified ability to muons ,this is more useful for the channels which include muon/muons in the final state. And better vertexing.Our MC goals Studying the feasibility of research of Bc meson at the CMS Study

8、ing the events select strategy of the Bc reconstruction Estimating the number of Bc events available at the CMS Studying the system errorPreparing for the near future experiment!List of CMS SoftwareThe CMS software was downloaded and installed in our home machine successfully. The version of the CMS

9、 software are being used in our home machines are OSCAR_3_7_0 ORCA_8_7_3The Installation of CMS SoftwareBcJ/ (J/)Display of Bc eventsDisplay of Bc eventsBcJ/ (J/)The CMS Analysis chainMC generatorHEPEVTNtupleOSCAR OSCARNtuplesignalNtupleminbiasPOOLSimHits/signalPOOLSimHits/minbiasPOOLDigisDSTROOTTre

10、e“data summary tape”UserSimReaderRecReaderRecReader1)digitization2)reconstruction3)analysisORCA MC generatorBc production: C.H. Chang X.G. Wu ITP BeijingBc decay and interface with OSCAR: G.M. Chen S.H. Zhang IHEP Beijing A.A. Belkov S. Shulga JINR Dubna (Russia)jetslJjetsBcbb2/2MC generatorcomparis

11、ion of Pt distributions of Bc mesonPYTHIA 1event/2 min. BCVEGPY 102 events/ min.Single lepton reconstruction efficiencyThe reconstructed efficiency of single muon/electron V.S. The Pt cut of the single muon/electron In order to get the reconstructed muon or electron as efficiency as enough,we requir

12、ein the generator level:For : Pt = 4.0GeV |Eta|= 4.0GeV |Eta|=2.2 Bc is generated with (pT10GeV,|eta|2) The production cross section is =10.6nb (including 11S0 ,13S0)GeneratorBcJ/ (J/ (J/ ) )| | | | 2.2Generator Level Muon pT Cut EfficiencySimulation (OSCAR) Reconstruction (ORCA)AnalysisResultsGener

13、ator (Ntuple)BcJ/+ l (or ) J/l+l- J/ Selection 2 leptons Pt 4.0 GeV2 leptons share the same vertex2 leptons have different charge2 leptons invariant mass around the J/ Selection of the Lepton from Bc BcJ/+ l J/l+l- Be identified as a muon or a electron Pt 4.0 GeV come from the same vertex (J/ vertex

14、)Bc Signal Reconstructed ResultsM(+-) (GeV/c2)J/ Mass (GeV/c2) BcJ/ (J/ (J/ ) )Bc Signal Reconstructed Results BcJ/ (J/ (J/ ) )1/Ptrec 1/Ptgene (GeV-1) from Bc directlyBcJ/Events Selection Study (1). J/ Selection is as before. (2). for pion, we required: Be not identified as a lepton Pt 2 GeV Share

15、the same vertex with 2 leptons (J/ vertex) Bc Signal Reconstructed Results BcJ/ (J/ (J/ ) )M(+-) (GeV/c2)J/ Mass (GeV/c2)Bc Signal Reconstructed Results BcJ/ (J/ (J/ ) )1/Ptrec 1/Ptgen (GeV-1)1/Ptrec 1/Ptgen (GeV-1) from BcBcBackgrounds StudyWe dont have enough computing power LHC Computing GridIHEP

16、,BEIJINGCERN INFNA series of Datasets of backgrounds we need are stored in CERN, CNAF, etc.Backgrounds StudyBackground ChannelCross sectionNumber of Simulated EventsNumber of Events we get from INFN and CERN using Grid B0s J/(J/) 167 pb 198275 198275B J/X (J/) 51.4 nb 200750 200750bb X 4.8 nb 99736

17、99736QCD pt15_20(udsg ) pt20_30 pt30_50 pt50_80 1.5 mb 0.64 mb 0.156 mb 0.021 mb 44999 89999 287747 433743 44999 89999 24000 223743The backgrounds which have been transmitted and studied by now includes:Background ChannelBcJ/ (J/ )BcJ/e (J/ )BcJ/ (J/ )B0s J/(J/) 7 (59) 10 (84) 22 (185)B J/X(J/) 7 (2

18、1072) 5 (15051) 17 (51174)bbX 0 0 1 (534)QCD (udsg ) pt15_20pt20_30pt30_50 pt50_80 Backgrounds StudyNumber of Events in the integrated Luminosity of 10 fb-1Backgrounds StudyAfter event select and CMS HLT, the effect of background B0s J/(J/) to the Bc channel BcJ/(J/)Bc signalBackgrounds StudyAfter e

19、vent select and CMS HLT, in the integrated Luminosity of 10 fb-1 , the background B0s J/(J/) V.S. Bc signal BcJ/(J/)Summary (I)1. BcJ/l(J/l+l-)2. BcJ/(J/l+ l-)1. Preliminary Events Select (for the search of Bc at the CMS experiment)1)Pt (lepton) 4.0GeV.2)3 leptons shared the same vertex.3)The invari

20、ant mass of a pair of leptons (l+l-) which have different charges is around J/. e.g. |M(+-) M(J/)| 0.2GeV4)For the uncertainty of the losing of neutrino, we take the range3.0GeV,7.0GeV as our signal region of J/l.5)For CMS HLT, required: Single : Pt 19GeV Double : Pt 7GeV Single e: Pt 29GeV Double e

21、: Pt 17GeV 1)2 leptons (from J/) Pt (lepton) 4.0GeV ,share the same vertex, have different charge Invariant mass of the 2 leptons is around J/2)Pion selection The particle is not identified as a lepton Pt 2.0GeV , shares the same vertex of J/ Pion candidate is isolated in the cone 3) For CMS HLT.0.2

22、R22)()(Summary (II)2. Number of Bc events available at the CMS experimentDecay channelNumber of events at generator level Number of Reconstructed events (CMS HLT)Number of Events at 10 fb-1 (CMS HLT)BcJ/(J/) 1.18*106 3517 6318BcJ/e(J/) 6.2*105 562 2054BcJ/(J/ee) 7.6*105 94 262BcJ/e(J/ee) 9.2*105 23 53BcJ/(J/) 4.8*105 2426 1071BcJ/(J/ee) 4*105 28 19 total 9777 (S-wave)3. Bc study in CMSSummary (III)Afte