1. 10 TeV BJ/K at CMS
Zheng Wang
Apr. 2009

2. 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

3. 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+)=(1.0080.035)×10-3; Br(J/)=(5.930.06)×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

4. HLT efficiency
24. Mar. 2009
Zheng Wang

5. 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

6. Muon and J/
 39.1 MeV
M3.12 GeV
24. Mar. 2009
Zheng Wang

7. Plots for Vertex kinematic fit
Prob>0.001
24. Mar. 2009
Zheng Wang

8. B mass
14 TeV
45.6MeV
22.5MeV
10 TeV
24. Mar. 2009
Zheng Wang

9. 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

10. 24. Mar. 2009
Zheng Wang

11. 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. BJ/ and BJ/+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

12. Full efficiency(HLT_DoubleMu3)
24. Mar. 2009
Zheng Wang

13. Full eff. and X-section
24. Mar. 2009
Zheng Wang

14. 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

15. Next/ongoing sys. uncertainty determination; Background. Thanks.
24. Mar. 2009
Zheng Wang

16. backup
24. Mar. 2009
Zheng Wang