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10 TeV BJ/K at CMS Zheng Wang Apr. 2009
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The data sample BtoJpsiMuMu: Generated with CMSSW_2_1_7 or CMSSW_2_1_8
/BtoJpsiMuMu/Summer08_IDEAL_V9_v2/GEN-SIM-RECO , 2,434,076 events, (T2_US_Purdue, T2_CH_CSCS, T1_DE_FZK, T2_CN_Beijing) Generated with CMSSW_2_1_7 or CMSSW_2_1_8 We used 992,800 events to perform the following analysis, corresponding to 43.5pb-1 data. 24. Mar. 2009 Zheng Wang
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How to get the cross-section?
Filter N(B+obs): Fit the Inv. mass of J/ and K spec., subtracting the background. Br(B+J/K+)=(1.0080.035)×10-3; Br(J/)=(5.930.06)×10-2; L: Int. luminosity. tri = N pass J/ trigger / Ninit. B rec : B meson reconstruction efficiency after the corrections. 24. Mar. 2009 Zheng Wang
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HLT efficiency 24. Mar. 2009 Zheng Wang
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B reconstruction: Selection Criteria
Use the combination of J/ and on charged track to reconstruct B meson, CMS can not PID. At least two globalMuon candidates with ||< 2.5 and Pt>2.5GeV/c . Muon pairs reconstruct the J/ meson, the pair with the inv. mass closest to the J/ mass is selected. The m() in GeV/c^2. The other charged tracks Pt are required to be greater than 2.0 GeV/c , ||< 2.5, and are considered to be kaon particle. Two muons from J/psi and one charged tracks are performed a kinematic vertex fit, the Prob(fit) > in the fitting, the inv. mass of two muons is constrained to be J/ mass, three tracks derive from common vertex. 24. Mar. 2009 Zheng Wang
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Muon and J/ 39.1 MeV M3.12 GeV 24. Mar. 2009 Zheng Wang
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Plots for Vertex kinematic fit
Prob>0.001 24. Mar. 2009 Zheng Wang
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B mass 14 TeV 45.6MeV 22.5MeV 10 TeV 24. Mar. 2009 Zheng Wang
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Differential X-section d/dpT(B)
Start the measurement from 9 GeV/c, 7 Pt bins, Try to make observed B meson in each bins to be same. 24. Mar. 2009 Zheng Wang
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24. Mar. 2009 Zheng Wang
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Fit technique Extract signal in each pT bin by 1-D maximum LH fit to B mass; One Gaussian for B mass with a linear bg; Short mass fitting range as CDFII’s analsyis to decrease the sys. error from bg. Shape. Do not think using triple gaussian will be better, when running on real data, the bg. BJ/ and BJ/+X with very soft will contaminate the signal. 2D(mass+ct) fit do not help to extinguish the signal and bg. Prompt J/ contribute a random bg in B mass spectrum. 24. Mar. 2009 Zheng Wang
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Full efficiency(HLT_DoubleMu3)
24. Mar. 2009 Zheng Wang
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Full eff. and X-section 24. Mar. 2009 Zheng Wang
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Both Mass and mass reso. are almost independent on B meson pT
B performance PDG value Both Mass and mass reso. are almost independent on B meson pT 24. Mar. 2009 Zheng Wang
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Next/ongoing sys. uncertainty determination; Background. Thanks.
24. Mar. 2009 Zheng Wang
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backup 24. Mar. 2009 Zheng Wang
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