1. Z. X. Zhang , G. M. Chen, X. Y. Wang, et al 2009/11/27
Bc->J/Ψπ
Z. X. Zhang , G. M. Chen, X. Y. Wang, et al
2009/11/27

2. contents Compare two kinds of selection method of Jpsi
Bg distribution in region of Bc mass: 3.0GeV to 7.1GeV
2-dim RooFit of Bc: whole and binned Pt
Several RooFit Plots

3. Compare two kinds of selection method of Jpsi
we select two muon with largest Pt to reconstruct Jpsi , instead of the pair with closest invariant mass to Jpsi mass. This just only brings difference to QCD bg, and not a little to signal and other bg.
Method 1:
Closest inv mass
Method 2:
Largest Pt
QCD
QCD
Mass of Jpsi

4. Bg distribution in region of Bc mass: 3.0GeV to 7.1GeV
If we use cut of Lxy/δ>3, we can obtain more clean signal other than sideband bg.
B →J/Ψ K
Lxy/δ
use Lxy/δ>3
But we didn’t use this cut of Lxy/δin the last 2-dim fitting, because it can change the shape of lifetime.

5. 2-dim RooFit of whole regin Pt of Bc
Events used ( Limunosity)
signal , (175 pb-1)
inclusive B 10,773, (99.76 pb-1)
Prompt Jpsi 11,049, (9.59 pb-1)
Input events
Fitted events
Signal
4884
4619±85 bg
11312
11324±118
2 dimension fitted:
Mass: 3 Gauss + flat bg
Lifetime: exp(-t/τ)*2Gauss+2Gauss bg

6. 2-dim RooFit of each Pt bin of Bc
Comparison of events number between input and fitted
Pt bin of Bc
<14
GeV
14-16
16-18
18-20
20-22
22-24
24-26
26-28
28-30
30-32
32-34
34-36
36-38
38-40
>40
input
564
439
396
414
416
394
319
328
275
239
181
168
141
108
502
fitted
463±40
368±26
349±23
365±22
397±23
359±21
299±19
310±18
267±17
228±16
186±14
164±13
142±12
110±11
504±23
Efficiency of Pt
Pt of Bc

7. Several RooFit Plots
16-18GeV
<14GeV
32-34GeV
22-24GeV
38-40GeV

8. That's all, thank you.

9. Main selection criteria of Bc->J/Ψπ
Pt(μ)>2.5GeV, |η|<2.5
closest invariant mass of μμ
J/Ψ->μμKalmanVertexFitter
|M(μμ)-3.09|<0.1GeV
2. πselection
Pt(π)>2.0GeV , | η |<2.5
Delta_R (J/Ψ, π)<1.6
Remove overlap (π,μ)
Remove fake π from electron and muon by requiring DeltaR>0.05
nHits of pion track >10
3 . Bc->J/Ψπ:
Bc->J/Ψπ: KinematicParticleVertexFitter
Prob>0.01
Cos(α)>0.9: αis anglular between momentum of Jpsi and Pvetex-Svertex.
Based on cmssw_3_1_2

10. Generation information
Pt of Jpsi
Pt of muon
Pt of pion
Pt of Bc

11. Looking for cuts
Pt(track)>2.0GeV
Delta_R(J/Ψ, π)<1.6

12. nHits of pion>10 Pt of Bc>14GeV
Cosin of angle between dl and Jpsi >0.9

13. M(J/Ψπ)
M(μμ)
PDL
Lxy

14. Other possibly useful information
Lxy/σ
Pt of Jpsi
Chi2/ndf of pion

15. 2-dim fit Floating Parameter FinalValue +/- Error GblCorr.
sigma_{M0} e-01 +/ e
sigma_{M1} e-02 +/ e
sigma_{M2} e-02 +/ e
sigma_{t0} e-03 +/ e
M_{0} e+00 +/ e
M_{1} e+00 +/ e
M_{2} e+00 +/ e
N_{Bc} e+03 +/ e
N_{IncB} e+03 +/ e
ctau_{Bc} e-02 +/ e
f1_g_sigma_{t0} e-01 +/ e
f_g0_M e-02 +/ e
f_g1_M e-01 +/ e
s_{to} e+00 +/ e
2-dim fit

16. Cuts flow Bc->J/Ψπ inclusiveB PromptJpsi QCD Cross section
8778 *0.13/1.9 pb
1.08 *105pb
*106 pb
*106pb
Events used
(corresponding to L)
107,763
(175pb-1)
10,773,588
(99.76pb-1)
11,049,047
(9.59pb-1)
878,375
(0.8pb-1)
triggerbit_HLTdoubleMu3
33077
458799
145507
85777
|M(MuMu)-3.09|<0.1
32125
417156
138859
2782
No of Bc>0
7570
24930
4355
283
ChiProb>0.01
7060
17777
3878
173
CosAlpha(Jpsi and dl)>0.9
6187
16720
1483 16
nHits of pion>10
5610
14323
1277
Pt of Bc>14.0
4935
6538
493
6.10<M(Bc)<6.44GeV
4391
1400
117
Nomorlized to 100pb-1
2509
1403
1220

17. Next to do
Cross section measurement
Optimize cuts, efficiency