Feasibility to Study the Bc Meson at CMS

Feasibility to Study the Bc Meson at CMS Tao Junquan CMS Group Institute of High Energy Physics, Chinese Academy of Science 1 st Chinese-French Workshop 14 December, 2006 1

Outline • Introduction • Process & results – MC Production of Bc signal & backgrounds – Event selection, by studying Bc signal & backgrounds – Results • Summary & Outlook (for real data) 1 st Chinese-French Workshop 14 December, 2006 2

Introduction 1 st Chinese-French Workshop 14 December, 2006 3

Bc Meson • The Bc meson is the lowest-mass bound state of a charm quark and a bottom anti-quark. It is the latest such meson predicted by the Standard Model. • Because Bc meson carry flavor, it provides a new window for studying heavy-quark dynamics for the two different heavy quarks, which is very different from the window provided by quarkonium. • Its mass is predicted to be And its lifetime is predicted to be between 0. 4 and 0. 7 ps V. V. Kiselev, PACS number: 13. 20. Gd, 13. 25. Gv, 11. 55. Hx 1 st Chinese-French Workshop 14 December, 2006 4

TEVATRON: CDF (1998) 20 J/ψ lυ events, mass : 6. 40± 0. 39± 0. 13 Ge. V life time : ps 1 st Chinese-French Workshop 14 December, 2006 5

Recent results of Bc Meson Experimental observation (CDF & D 0 , Tevatron) 1998 2004 2005 1 st Chinese-French Workshop 14 December, 2006 6

CMS Experiment Large Hadron Collider 2008 CMS 1 st Chinese-French Workshop 14 December, 2006 7

CMS Detector 1 st Chinese-French Workshop 14 December, 2006 8

Adavantages of study Bc at CMS 1. Higher Collide Energy LHC: PP collider 2. Larger detector region than CDF The CMS detector has the similar structure as CDF , but it has larger detector region than CDF. CMS: eta~(-2. 5, 2. 5) CDF: eta~(-1. 0, 1. 0) (RUN I) eta~(-1. 5, 1. 5) (RUN II) (Muon system) 3. A better identification ability to muons The CMS detector has a better identification ability to muons , this is more useful for the channels which include muon/muons in the final state. 1 st Chinese-French Workshop 14 December, 2006 9

Goal & status • The goal: to measure the mass and life time of Bc • The first channel to look: Bc → J/ψ π (J/ψ → µµ) • First publication at about 1 fb-1 1 st Chinese-French Workshop 14 December, 2006 10

Process & results 1 st Chinese-French Workshop 14 December, 2006 11

The CMS Analysis chain MC generator HEPEVT Ntuple OSCAR ORCA OSCAR 1)digitization 2)reconstruction Sim. Reader Ntuple signal Ntuple minbias Rec. Reader POOL Sim. Hits/signal POOL Digis Sim. Hits/minbias 3)analysis ROOT Tree “data summary tape” DST User 1 st Chinese-French Workshop 14 December, 2006 12

The CMS Fast Simulation HEPEVT Ntuple MC generator FAMOS POOL Ntuple Simulation, Digis, and DST ROOT Tree 1 st Chinese-French Workshop 14 December, 2006 13

Generator of Bc signal • BCVEGPY IPT, Beijing, by Chang et al. • Russian package IHEP, Protvino, by Berezhnoy et al. • PYTHIA BCVEGPY is used: faster agrees well with PYTHIA 1 st Chinese-French Workshop 14 December, 2006 14

Bc signal About 30 1/fb Bc events were produced for efficiency study with both OSCAR/ORCA and FAMOS Particle Decay channels σ (pb) Generated (*104) Bc Bc→J/ψπ (J/ψ→µµ ) 1. 781 5. 2082 kine cut : Bc Pt≥ 10 Ge. V |eta|≤ 2. 0 Mu Pt≥ 4 Ge. V |eta|≤ 2. 2 Pion Pt≥ 2 Ge. V |eta|≤ 2. 4 Another independent 1/fb Bc were produced as data OSCAR_3_7_0 ORCA_8_7_3 FAMOS_1_3_2 1 st Chinese-French Workshop 14 December, 2006 15

Backgrounds 1. Other B hadrons’ decay include J/ψ 2. Prompt J/ψ 3. ccbar→μμx 4. bbbar →μμx 5. General QCD, W+jets, Z+jets 1 st Chinese-French Workshop 14 December, 2006 16

Backgrounds (1, 2, 3) generated by CMKIN & produced by FAMOS at local 1 st Chinese-French Workshop 14 December, 2006 17

Backgrounds (4, 5) We don’t have enough computing ability. A series of Datasets of backgrounds we need are stored in CERN, CNAF, etc. CRAB CERN INFN IHEP, BEIJING LHC Computing Grid 1 st Chinese-French Workshop 14 December, 2006 18

bb→μμx background CMS official production with OSCAR/ORCA Dataset bt 03_B 0 s. Comb. Bkg (bb→mumu+ X) σ(mb) 4. 8*10 -3 Nevents 100, 000 Kine cut: muon: Pt>2 Ge. V |μ|<2. 5 2 muons invariant mass : (2. 5, 3. 5) Ge. V 1 st Chinese-French Workshop 14 December, 2006 19

QCD CMS official production with OSCAR/ORCA Dataset σ(mb) No. of events getted using Grid jm 03 b_qcd_0_15 55. 22 23999 jm 03 b_qcd_15_20 1. 50006 44999 jm 03 b_qcd_20_30 0. 641733 89999 jm 03 b_qcd_30_50 0. 155929 92997 jm 03 b_qcd_50_80 0. 02093883 198993 jm 03 b_qcd_80_120 0. 002949713 90000 jm 03 b_qcd_120_170 0. 000499656 70000 jm 03 b_qcd_170_230 0. 000100995 40000 jm 03 b_qcd_230_300 2. 3855*10 -5 50000 jm 03 b_qcd_300_380 6. 39108*10 -6 243983 jm 03 b_qcd_380_470 1. 88967*10 -6 5000 Total QCD events: 950, 000 1 st Chinese-French Workshop 14 December, 2006 20

W+jets CMS official production with OSCAR/ORCA Dataset σ(mb) No. of events getted using Grid jm 03 b_Wjets_0_20 1. 110015*10 -4 150000 jm 03 b_Wjets_20_50 2. 729528*10 -5 200000 jm 03 b_Wjets_50_85 1. 006911*10 -5 200000 jm 03 b_Wjets_85_150 6. 306967*10 -6 200000 jm 03 b_Wjets_150_250 1. 20248*10 -6 100000 jm 03 b_Wjets_250_400 2. 632455*10 -7 30000 Total W+jets events: 880, 000 1 st Chinese-French Workshop 14 December, 2006 21

Z+jets CMS official production with OSCAR/ORCA Dataset σ(mb) No. of events getted using Grid jm 03 b_Zjets_0_20 3. 160245*10 -5 200000 jm 03 b_Zjets_20_50 5. 1666367*10 -6 200000 jm 03 b_Zjets_50_85 1. 45609*10 -6 110000 jm 03 b_Zjets_85_150 5. 76427*10 -7 100000 jm 03 b_Zjets_150_250 1. 61726*10 -7 30000 jm 03 b_Zjets_250_400 3. 66168*10 -8 70000 Total Z+jets events: 710, 000 1 st Chinese-French Workshop 14 December, 2006 22

Selection I J/Ψ candidates: 2 muons Pt ≥ 4. 0 Ge. V , |η|<=2. 2 2 muons share the same vertex 2 muons have different charge 2 muons’ invariant mass around the J/Ψ [3. 0, 3. 2]Ge. V 1 st Chinese-French Workshop 14 December, 2006 23

Comparing of 2 muon’s invariant mass of OSCAR/ORCA and FAMOS _____ 10 fb-1 10/fb Full Simulation : 3829 _____ Fast Simulation : 3371 Normalized to 10 fb-1 , the number of reconstructed J/Ψ of the full simulation is about 12% more than that of fast simulation, the shape agrees well 1 st Chinese-French Workshop 14 December, 2006 24

Selection II Pion candidate: Be not identified as a lepton Pt ≥ 2 Ge. V |η|<=2. 4 Share the same vertex with 2 muons (J/Ψ vertex) 1 st Chinese-French Workshop 14 December, 2006 25

Selection III Signal selection cuts: • cos(thetasp)>0. 8 thetasp: is the angle between the direction from the primary to the second vertex the direction of the reconstructed Bc momentum • PDLxy >60 μm • PDLxy /σxy >2. 5 1 st Chinese-French Workshop 14 December, 2006 and 26

1 fb-1 1 st Chinese-French Workshop 14 December, 2006 27

Selection IV Bc mass window (6. 25, 6. 55) Ge. V 1 st Chinese-French Workshop 14 December, 2006 28

Cuts and Selections Cumulative Eff. Nevents Passed total: 52082 Dimu and J/ψ 32. 88% 17127 Pion 15. 07% 7851 Lxy/σxy >2. 5 7. 07% 7. 04% 6. 98% 3685 3666 3637 6. 93% 3608 Cos(θsp)>0. 8 PDL >60μm Bc candidate in mass[6. 25, 6. 55] 1 st Chinese-French Workshop 14 December, 2006 29

Summary Bc 120± 11 B+ 0. 7± 0. 2 Bs 0. 1 B 0 0. 9± 0. 3 Prompt J/ψ 0. 1 QCD 0. 7± 0. 1 Λb 0. 1 ccbar 0. 01 bbbar 0. 01 1 st Chinese-French Workshop 14 December, 2006 1 fb-1 Total 2. 6± 0. 4 30

uncertainty of Bc number source: 1. LO only 2. color singlet only (no color-octet available) 3. Values of inputs mass of b quark, c quark ; parton distribution function (pdf). 1 st Chinese-French Workshop 14 December, 2006 31

Kinematic fitting Bc→J/ψπ, J/ψ→μμ Totally 3 tracks: 2 muon tracks: J/ψ mass constraint all the 3 tracks: share the same 1 st Chinese-French Workshop 14 December, 2006 vertex 32

M(Bc): 6402. 0± 22. 0 Me. V Input: 6400 Me. V cτ(Bc): 148. 8± 13. 1 μm Input 150 μm 1 st Chinese-French Workshop 14 December, 2006 33

Systematic error source: • Misalignment 1. muon momentum scale uncertainty 2. muon momentum resolution deterioration 3. vertex resolution deterioration • Efficiency uncertainty • Theoretical uncertainty • Cuts sensitivity 1 st Chinese-French Workshop 14 December, 2006 34

Summary of systematic error Bc mass (Me. V) Bc cτ (μm) P scale 11 0. 2 P smear 10 0. 8 / 2. 4 Cuts 0. 1 0. 2 Efficiency / 0. 1 Vertex smear Theoretical Total / 1. 5 14. 9 1 st Chinese-French Workshop 14 December, 2006 3. 0 35

Muon momentum resolution CMS 1/fb: Mass: 22. 0(fit) ± 14. 9(syst) Me. V lifetime: 0. 044(fit) ± 0. 010(syst) ps 1 st Chinese-French Workshop 14 December, 2006 36

Summary & Outlook 1 st Chinese-French Workshop 14 December, 2006 37

Summary n. With MC data, the feasibility for CMS to measure the mass and the lifetime of Bc meson was studied. n. The study focus on the decay channel Bc→J/ψπ. n 120 events can be selected with the first 1 fb-1 data n. Mass resolution is estimated to be ncτ resolution is corresponding to the lifetime error to be n. Uncertainty: effects of misalignment, theoretical uncertainty on the Bc Pt distribution, and limited Monte Carlo statistics. n. The results had been written into the CMS Note, and can be available from http: //cmsdoc. cern. ch/doc/notes/docs/NOTE 2006_118 the website 1 st Chinese-French Workshop 14 December, 2006 38

Outlook (For the real data in 2008) • J/ψ+ 1 track will be selected as a control sample • B+ → J/ψ+K+ will be used to estimate the Bc efficiency • J/ψ peak side band will be used for the Bc background estimation 1 st Chinese-French Workshop 14 December, 2006 39

The End Thanks ! 1 st Chinese-French Workshop 14 December, 2006 40

Backup slides 1 st Chinese-French Workshop 14 December, 2006 41

Cross section comparison • Bc vs other B σ(other B) =1000 σ( Bc) • LHC vs TEVATRON 20 times larger Pt cut (Ge. V) 0 5 50 100 TEVATRON/LHC 6. 3% 5. 2% 1. 0% 0. 3 % H. C. Chang X. G. Wu 1 st Chinese-French Workshop 14 December, 2006 42

Bc decay and interface with OSCAR: Force Bc to decay with the final states we need and interface with OSCAR (Implemented within SIMUB ) SIMUB is one of CMS Supported generator packages , which is dedicated for simulation of B-meson production and decays. http: //cmsdoc. cern. ch/~shulga/SIMUB. html G. M. Chen A. A. Belkov S. H. Zhang IHEP Beijing S. Shulga JINR Dubna (Russia) 1. Bc→J/Ψlν(J/Ψ→l+l-) n. Bc→J/ψµν(J/ψ→µµ) n. Bc→J/ψeν(J/ψ→µµ) n. Bc→J/ψµν(J/ψ→ee) n. Bc→J/ψeν(J/ψ→ee) 2. Bc→J/Ψπ(J/Ψ→l+ l-) n. Bc→J/ψπ(J/ψ→µµ) 1 st Chinese-French n. Bc→J/ψπ(J/ψ→ee) Workshop 14 December, 2006 43

Background of Bc→J/ψπ (J/ψ→µµ) from B 0 Number decay channels Branch Ratio Nev σ(pb)after Kine cut 5110 B 0 → JPsi + K 0 0. 08% 170000 16. 040 5111 B 0 → JPsi + K 0* 0. 14% 290000 28. 288 5112 B 0 → chi_c 1 + K 0 0. 19% 120000 11. 192 5113 B 0 → chi_c 1+ K 0 * 0. 25% 150000 14. 808 channels Branch Ratio JPsi → mu+ mu- 5. 88% chi_c 1 → JPsi + γ 31. 6% K 0* → Random K- Pi+ K 0 Pi 0 K 0 γ 66. 5% 33. 3% 0. 2% Kinematic cuts at generator llevel Mu: pt ≥ 4. 0 Ge. V |eta| ≤ 2. 4 K: pt ≥ 2. 0 Ge. V |eta| ≤ 2. 7 -1 bkg from Workshop More than 101 stfb. Chinese-French B 0 were produced 14 December, 2006 44

Background of Bc→J/ψπ (J/ψ→µµ) from B+ Number decay channels Branch Ratio Nev σ(pb) after kine cut 5210 B+ → JPsi + K+ 0. 08% 170000 16. 056 5211 B+ → JPsi + K+* 0. 14% 290000 28. 611 5212 B+ → chi_c 1 + K+ 0. 19% 120000 11. 150 5213 B+ → chi_c 1+ K+* 0. 25% 150000 14. 921 channels Branch Ratio JPsi → mu+ mu- 5. 88% chi_c 1 → JPsi + γ 31. 6% K+* → Random K 0 Pi+ K+ Pi 0 K+ γ 66. 6% 33. 3% 0. 1% Kine cut: Mu: pt ≥ 4. 0 Ge. V |eta| ≤ 2. 4 K: pt ≥ 2. 0 Ge. V |eta| ≤ 2. 7 Chinese-French More than 10 fb-11 st bkg from. Workshop B+ were produced 14 December, 2006 45

Background of Bc→J/ψπ (J/ψ→µµ) from Bs Number decay channels Branch Ratio Nev σ(pb) after kine cut 5310 Bs → JPsi + phi 0. 14% 30000 2. 215 5311 Bs → JPsi + eta 0. 04% 40000 3. 198 5312 Bs → JPsi + eta’ 0. 04% 30000 2. 968 5313 Bs → chi_c 1+ eta 0. 1% 30000 2. 064 5314 Bs → chi_c 1+ eta’ 0. 09% 20000 1. 738 5315 Bs → chi_c 1+ phi 0. 25% 30000 2. 583 channels Branch Ratio JPsi → mu+ mu- 5. 88% phi → K+ K- 48. 9% chi_c 1 → JPsi + γ 31. 6% eta → Random 1 eta’ → Random 1 Kine cut Mu: pt ≥ 4. 0 Ge. V |eta| ≤ 2. 4 K: pt ≥ 2. 0 Ge. V |eta| ≤ 2. 7 Chinese-French Workshop More than 10 fb-11 st bkg from Bs were produced 14 December, 2006 46

Background of Bc→J/ψπ (J/ψ→µµ) from Λ 0 b Number decay channels Branch Ratio Nsel σ(pb) after kine cut 51220 Lambda_b 0 → JPsi + Lambda 0 0. 22% 130000 12. 797 51221 Lambda_b 0 → chi_c 1+ Lambda 0 0. 44% 70000 6. 642 channels Branch Ratio JPsi → mu+ mu- 5. 88% chi_c 1 → JPsi + γ 31. 6% Kine cut Mu: pt ≥ 4. 0 Ge. V |eta| ≤ 2. 4 Lambda 0 → Random More than 10 fb-1 bkg from Λb were produced 1 st Chinese-French Workshop 14 December, 2006 47

Background of Bc→J/ψπ (J/ψ→µµ) from prompt J/ψ Number 4430 4431 decay channels g (γ) + g (γ) → JPsi Chi_c 0 Chi_c 1 Chi_c 2 Branch Ratio N(sel) σ(pb) after kine cut 5. 88% 0. 7% * 5. 88% 31. 6% * 5. 88% 13. 5% * 5. 88% 10000 40000 180000 0. 440 0. 794 3. 902 17. 553 260000 217. 57 g (q) + g (q) → c cbar + g (q) channels 5. 88% Branch Ratio JPsi → mu+ mu- 5. 88% chi_c 0 → JPsi + γ 0. 7% chi_c 1 → JPsi + γ 31. 6% chi_c 2 → JPsi + γ Kine cut: Mu: pt ≥ 4. 0 Ge. V |eta| ≤ 2. 4 More than 10 fb-1 bkg from 4430 were produced. 13. 5% Only 1 fb-1 events from Channel 4431 1 st Chinese-French Workshop 48 14 December, 2006

(1) PYTHIA 1 st Chinese-French Workshop 14 December, 2006 49

(2) PYTHIA 1 st Chinese-French Workshop 14 December, 2006 50

Backgound estimation None of the QCD, W+jets, Z+jets, ccbar and bbbar passed the selection. As the number of events produced is less than one 1/fb, the number of background events from these samples will be estimated step by step 1 st Chinese-French Workshop 14 December, 2006 51

QCD background estimation selection efficiency 1. two muons p. T>4 Ge. V, |η|<2. 2 ε(2μ) 2. J/ψreconctruction same vertex, mass(μμ) : (3. 0, 3. 2) ε(rec) 3. Final cuts Lxy/σ>2. 5, PDL>60μm cos(thesp)>0. 8 mass(J/ψ, π): (6. 25, 6. 55) ε(prompt) The total efficiency is ε(2μ)*ε(rec)* ε(prompt) 1 st Chinese-French Workshop 14 December, 2006 52

Dataset σ(mb) No. of events getted using Grid No. of Single Mu (>= 1 Mu) No. of Double Mu (>= 2 Mu) jm 03 b_qcd_0_15 55. 22 23999 10 0 jm 03 b_qcd_15_20 1. 50006 44999 122 1 jm 03 b_qcd_20_30 0. 641733 89999 461 4 jm 03 b_qcd_30_50 0. 155929 92997 933 12 jm 03 b_qcd_50_80 0. 02093883 198993 4382 126 jm 03 b_qcd_80_120 0. 002949713 90000 3408 147 jm 03 b_qcd_120_170 0. 000499656 70000 3872 248 jm 03 b_qcd_170_230 0. 000100995 40000 3130 247 jm 03 b_qcd_230_300 2. 3855*10 -5 50000 4963 453 jm 03 b_qcd_300_380 6. 39108*10 -6 243983 31873 3769 jm 03 b_qcd_380_470 1. 88967*10 -6 5000 744 111 Kine cut: Mu: pt ≥ 4. 0 Ge. V |eta| ≤ 2. 2 1 st Chinese-French Workshop ε(2μ) can be estimated from QCD samples 14 December, 2006 53

ε(rec) estimation • Using ccbar→μμx sample total: 210, 000 The number of events pass 2 muon selection: 147778, reconstructed J/ψ: 192 ε(rec)= (1. 3± 0. 1) × 10 -3 1 st Chinese-French Workshop 14 December, 2006 54

ε(prompt) estimation • Using prompt J/ψ sample • The number of events pass the above selection is 434, 566 • Enlarge the mass window from (6. 25, 6. 55) to (5. 0, 8. 0), 27 events obtained assuming random distribution of the 27 events ε(prompt)=(6. 55 -6. 25)/(8 -5)*27/434566= (6. 2± 1. 2) × 10 -6 1 st Chinese-French Workshop 14 December, 2006 55

Prompt J/ψ 1 st Chinese-French Workshop 14 December, 2006 56

QCD background contribution Dataset σ(mb) ε(2 mu) Total ε N 1 fb-1 jm 03 b_qcd_0_15 55. 22 (1. 736256 ± 0. 17363)e-7 (1. 40157 ± 0. 19937)e-15 0. 077 ± 0. 011 jm 03 b_qcd_15_20 1. 50006 (7. 35045 ± 0. 06025)e-6 (5. 93353 ± 0. 29930)e-14 0. 089 ± 0. 004 jm 03 b_qcd_20_30 0. 641733 (4. 444494 ± 2. 222247)e-5 (3. 58775 ± 1. 04850)e-13 0. 230 ± 0. 067 jm 03 b_qcd_30_50 0. 155929 (1. 290364 ± 0. 372496)e-4 (1. 04161 ± 0. 13080)e-12 0. 162 ± 0. 020 jm 03 b_qcd_50_80 0. 02093883 (6. 331881 ± 0. 56409)e-4 (5. 11131 ± 0. 25650)e-12 0. 107 ± 0. 005 (1. 31848 ± 0. 06467)e-11 0. 039 ± 0. 002 jm 03 b_qcd_80_120 0. 002949713 (1. 633333 ± 0. 134715)e-3 ε(2 mu→JPsi) = (1. 3± 0. 1) × 10 -3 -6 ε(JPsi →Bkg) = (6. 2± 1. 2 ) × 10 1 st Chinese-French Workshop 14 December, 2006 57

W+Jets has none Dataset σ(mb) ε(2 mu) Total ε N 1 fb-1 jm 03 b_Wjets_0_20 1. 110015*10 -4 (5. 13333 ± 0. 5850)e-4 (4. 14380 ± 0. 22887)e-12 (4. 5997 ± 0. 2541)e-4 jm 03 b_Wjets_20_50 2. 729528*10 -5 (1. 4350 ± 0. 08471)e-3 (1. 15838 ± 0. 05297)e-11 (3. 1618 ± 0. 1446)e-4 jm 03 b_Wjets_50_85 1. 006911*10 -5 (2. 880 ± 0. 120)e-3 (2. 32483 ± 0. 10225)e-11 (2. 34090 ± 0. 1030)e-4 jm 03 b_Wjets_85_150 6. 30697*10 -6 (4. 4650 ± 0. 149416)e-3 (3. 60430 ± 0. 15630)e-11 (2. 2732 ± 0. 0986)e-4 jm 03 b_Wjets_150_250 1. 20248*10 -6 (7. 740 ± 0. 27821)e-3 (6. 24799 ± 0. 27202)e-11 (7. 5131 ± 0. 3271)e-5 jm 03 b_Wjets_250_400 2. 632455*10 -7 (1. 123333 ± 0. 061192)e-2 (9. 0679 ± 0. 40713)e-11 (2. 3871 ± 0. 1072)e-5 ε(2 mu→JPsi) = (1. 299246± 0. 093765) × 10 -3 ε(JPsi →Bkg) = (6. 213095± 1. 19571 ) × 10 -6 1 st Chinese-French Workshop 14 December, 2006 58

Dataset σ(mb) ε(2 mu) Total ε N 1 fb-1 jm 03 b_qcd_120_170 0. 000499 656 (3. 54286 ± 0. 22497)e-3 (2. 85992 ± 0. 13235)e-11 0. 014 ± 0. 001 jm 03 b_qcd_170_230 0. 000100 995 (6. 1750 ± 0. 39291)e-3 (4. 98467 ± 0. 23076)e-11 0. 005 ± 0. 000 jm 03 b_qcd_230_300 2. 3855*1 0 -5 (9. 060 ± 0. 42568)e-3 (7. 31354 ± 0. 32511)e-11 0. 002 ± 0. 000 jm 03 b_qcd_300_380 6. 39108* 10 -6 (1. 54478 ± 0. 025162)e-2 (1. 24700 ± 0. 05301)e-10 0. 001 ± 0. 000 jm 03 b_qcd_380_470 1. 88967* 10 -6 (2. 220 ± 0. 210713)e-2 (1. 79206 ± 0. 09185)e-10 0. 000 ± 0. 000 Total QCD Bkgs: 0. 7 ± 0. 1 1 st Chinese-French Workshop 14 December, 2006 59

Z+jets background estimation • The probability for Z+jets to have fake prompt J/ψ: (3. 2 -3. 0)/(10 -0)*10/640, 000=3. 1*10 -7 • The probability for prompt J/ψ to fake Bc: (6. 2± 1. 2) *10 -6 • The total cross section: 38. 2 nb • The number of background at one 1/fb: 7. 4*10 -5 1 st Chinese-French Workshop 14 December, 2006 60

ccbar→μμx backgound estimation σ(mb) (ccbar→mumu+ X) 1. 69*10 -6 (ccbar→mumu+ X) Events n fb-1 Dimuon selection 210000 12. 426% σ(mb) ε(rec) 1. 69*10 -6 (9. 14286± 0. 65983) × 10 -4 147778 Total ε (5. 68054 ± 0. 23998) × 10 -9 J/ψselection 192 N 1 fb-1 0. 010± 0. 001 ε(JPsi →Bkg) = (6. 2± 1. 2) × 10 -6 1 st Chinese-French Workshop 14 December, 2006 61

bbbar→μμx backgound estimation Dataset σ(mb) ε(rec) bt 03_B 0 s. Comb. Bkg 4. 8*10 -6 (4. 2± 0. 6) (bb→mumu+ X) 10 -4 Total ε (2. 6± 0. 6) 10 -9 N 1 fb-1 0. 012± 0. 003 2% fb-1 bb→μμx produced, totally 100, 000 events, 42 events passed the dimuon and J/ψ selection 1 st Chinese-French Workshop 14 December, 2006 62

Zjets (pt 0_250) total events: 640, 000 1 st Chinese-French Workshop 14 December, 2006 63

Zjets (pt 0_250) total events: 640, 000 1 st Chinese-French Workshop 14 December, 2006 64

Muon momentum scale uncertainty Δ(1/p. T)=0. 0005/Ge. V (Albert De Roeck) Bc mass changes by 11 Me. V cτ changes by 0. 2 μm 1 st Chinese-French Workshop 14 December, 2006 65

Muon momentum resolution I. Belotelov et al CMS note 2006/017 Muon momentum were smeared according to This result Mass: 11 Me. V Ctau: 0. 8μm 1 st Chinese-French Workshop 14 December, 2006 66

Vertex resolution P. Vanlaer et al, CMS note 2006/029 Primary Vertex : x, y: smear 5. 7μm, z: 3. 7μm Second Vertex: x, y: smear 12. 4 μ m , z: 11. 4μm cτ: 2. 4 μ m 1 st Chinese-French Workshop 14 December, 2006 67

Cuts sensitivity • Momentum cuts changed by one σ • Other cuts changed by 10% mass: 0. 1 Me. V cτ : 0. 2 μm 1 st Chinese-French Workshop 14 December, 2006 68

Efficiency uncertainty To estimate the efficiency uncertainty sqrt(N) events subtracted , efficiency recalculated cτ: 0. 1 μm 1 st Chinese-French Workshop 14 December, 2006 69

Theoretical uncertainty Bc events were reweighted according their Bc p. T, so that the Bc p. T distribution agrees with Gouz’s distribution cτ: 2. 4μm 1 st Chinese-French Workshop 14 December, 2006 70