2010-04-18 ICSHEP 8, Apr. 17-19, 2010 1
CMS BOnia physics: J/Psi & Inclusive b(J/PsiX) production x-Section
Xiangwei Meng Guoming Chen
Institute of High Energy Physics, CAS, Beijing
The 8th ICSHEP, NanChang,China Apr 17-19, 2010
Apr. 18, 2010
2010-04-18 ICSHEP 8, Apr. 17-19, 2010 2
Outline
Motivations Data samples Analysis strategy Acceptance & efficiency Unbinned Combined MLH fit J/Psi production X-section Unfolding: J/Psi->Hb spectrum Systematic Uncertainties Summary
2010-04-18 ICSHEP 8, Apr. 17-19, 2010 3
Motivations
First measurement of Jpsi & b hadrons production x-section at sqrt(s) = 7(14) TeV
--the same strategy as CDFII’s on Jpsi & inclusive b measurement. Phys. Rev. D71 032001(2005)
Test of QCD calculations Essential measurement of background for many other proce
sses, validation of b-tagging
The meanwhile study on inclusive b lifetime calibrate resolution function understand calibration & alignment
2010-04-18 ICSHEP 8, Apr. 17-19, 2010 4
M.C. data samples
BtoJpsiMuMu 2.5M events ~100pb-1
JPsiMuMu 2.0M events ~16pb-1 InclusivePPmuX 5.3M events ~0.044pb-1
pp@10TeV
events normalized or scaled to: Inclusive b: 253,600 P-J/Psi: 1,150,000 Inclusive PPmuX: 5,132,579 Scale: 231.5->1,188,000,000
Early Data with 10 pb-1 analysis
2010-04-18 ICSHEP 8, Apr. 17-19, 2010 5
EvtGen: inclusive b
EvtGen with inclusive b → J/ΨX, J/Ψ → μμ Filter on 2 μ with pT>2.5 GeV/c, |η|<2.5
σgen_tot = 51.56 mb (@10TeV), Br(b → J/ΨX) = 0.0116 Br(J/Ψ → μμ) 0.0593 filterEfficiency ε= 0.0007139
σeff =σgen_tot*εfilter*Br = 25.36nb
2010-04-18 ICSHEP 8, Apr. 17-19, 2010 6
Event Reconstruction & selection
Global mu: pT> 3 GeV/c, |η|<2.4 KalmanVertexFitter on μ+μ- pairs, i.e. 2mus sharing
the same vertex Jpsi Mass window: [2.8, 3.4] GeV/c2
Further on ppdl: ppdl: [-0.1,0.5]cm, error_ppdl<0.1cm
2010-04-18 ICSHEP 8, Apr. 17-19, 2010 7
Measurement of b production Cross-secton
Re,corr corrTrig co
-
/Re Re/
/
( / ) ( / )
( , , , , )( ) T
bT
J corr corrp Trig co Trig coJ
b T JT
dBr b J Br J
dp
N Af p
Ldt p
L• dt : the integral luminosity
• fb : fraction for J/Ψ from b
• PT : the size of the PT bin.• : the number of reconstructed J/ signals • A: geometric and kinematic acceptance of J/ψ candidates• Trig, ,reco : trigger and recon efficiency from M.C. • : correction on trigger and recon efficiency from Tag&probe
The inclusive b differential cross-section is calculated as
/
T
JpN
Unfolding: pT Jpsi-> b
2010-04-18 ICSHEP 8, Apr. 17-19, 2010 8
Acceptances
Acceptances include the detector geometric and kinematic acceptances, Can be obtained by Monte Carlo simulation. is treated and defined as:
/ // /
/ /
( ,| | 2.4)( , )
( ,| | 2.4)
Rec J JJ J TT Gen J J
T
N pA p
N p
2010-04-18 ICSHEP 8, Apr. 17-19, 2010 9
Trig. Efficiency vs. pT : JPsi’s
L1MuOpen
. . .
1, 1
/ /1, 1
/ /
( ,| | 2.4)
( ,| | 2.4)
w r t Offline
L L HLT
Offline Glb J JL L HLT T
Offline Glb J JT
N p
N p
loose L1 mu trigger selection
•The L1T/HLT efficiency is calculated based on the numbers of an offline reconstructed J/psi passes or not corresponding triggers
2010-04-18 ICSHEP 8, Apr. 17-19, 2010 10
L1MuOpen
. . .
1, 1
/ /1, 1
/ /
( 5, )
( 5, )
w r t Offline
L L HLT
Offline Glb J JL L HLT T
Offline Glb J JT
N p
N p
Trig. Efficiency vs. η: JPsi’s
•The L1T/HLT efficiency is calculated based on the numbers of an offline reconstructed J/psi passes or not corresponding triggers
2010-04-18 ICSHEP 8, Apr. 17-19, 2010 11
Mass & ppdl fitting: resol. Model Sum08
Mass: 3Gaussion Pdl: 2Gaussion
2010-04-18 ICSHEP 8, Apr. 17-19, 2010 12
b ctau at Gen
Ctau_b: 467 micron
2010-04-18 ICSHEP 8, Apr. 17-19, 2010 13
Fit techniques: UCMLH fit (mass, ppdl)
a finite experimental resolution on each measurement
FR(t) = exp(-t/τ) ⊗ G(t,μ,σ) ≡ ε(t)· ∫ dt’ exp(-t’/τ) G(t-t’,μ,σ)
FE(t,dt) = ε(t)·exp(-t/τ) ⊗ G(t,μ,s⋅dt)
Offline p-jpsi: 11545 b: 4288
(t/dt) fitting with RooFit package
pT: 9-10GeV
Unbinned combined MLH fit & analysis method: 10pb-1 “data” PT: 5-40 GeV/c
FI(t) = exp(-t/τ)
2010-04-18 ICSHEP 8, Apr. 17-19, 2010 14
Fit results: Jpsi Pt bins 5-6, 30-40GeV/c
p-jpsi: 1060 b: 762
p-jpsi: 15126 b: 1801
2010-04-18 ICSHEP 8, Apr. 17-19, 2010 15
J/psi: b fraction & Acceptance, Trig eff.
Acceptance
Trig. Eff.
Unbinned combined MLH fit & analysis method: 10pb-1 “data” PT: 5-40 GeV/c
Reco “Data” J/psi
Prompt Jpsi(270k): 15280, 32380, 40792, 39592, 34183, 26992, 21016, 15768, 11764, 8671, 11603, 8691, 4884, 2579, 1074Jpsi(b hadrons)(68k): 1647, 4439, 6960, 8131, 8037, 7245, 6259, 5324, 4319, 3219, 4590, 3976, 2611, 1502, 749
2010-04-18 ICSHEP 8, Apr. 17-19, 2010 16
J/psi & b production x-section@pp 10TeV
J/psi pT spetrum -> b hadrons pT’s
J/Psi from b
Hb
pp → bbX ~ 430 μb (10 TeV)pp → bbX ~ 315 μb (7 TeV)
2010-04-18 ICSHEP 8, Apr. 17-19, 2010 17
Unfolding
Gen+filter J/psiGen+filter b hadron
Reco J/psi
Eff_Reco
Eff_Trig
Reco b hadron
Detector response
Gen b hadron
Unfolding
*Distortions between pT distribution of b hadrons and J/Ψ from them
2010-04-18 ICSHEP 8, Apr. 17-19, 2010 18
Unfolding methods I
Bin-to-bin correction: no into account migrations a bin to the others; neglect correlation between adjacent bins.
The matrix method: solve the problem of migrations; singular problem; statistical fluctuations; results unstable.
Regularized unfolding: satisfactory results but technical complications; only with one dimension
2010-04-18 ICSHEP 8, Apr. 17-19, 2010 19
Unfolding Method II: Bayes’ A Multidimensional unfolding method based on Bayes' theorem by
G.D'Agostini, Nucl. Instr. Meth. A362 (1995) 487-498.
Ci: cause in i-th bin:
Ej: effect in j-th binP(Ci|Ej): corelation matrix for Ej to Ci
2010-04-18 ICSHEP 8, Apr. 17-19, 2010 20
Unfolding correlation Matrix
/ _ [5,40]( )
( )
b J psi pT bGen T
Unfolding total bGen T
N p
N p
2010-04-18 ICSHEP 8, Apr. 17-19, 2010 21
J/psi pT spetrum -> b hadrons pT’s
( ,| | 2.4)( )
( ,| | 2.4)
Gen filter b bGen filter b T
T Gen b bT
N pp
N p
J/Psi from b
Hb
2010-04-18 ICSHEP 8, Apr. 17-19, 2010 22
Hb production x-section@pp 10TeV
GenGen+filter
2010-04-18 ICSHEP 8, Apr. 17-19, 2010 23
Systematic Uncertainties Luminosity ~10% Branching fractions ~9.6% Acceptance& efficiency
Jpsi polarization: CDF-II & BaBar 2-7% pT spetrum: flat pT distribution needed 0−5%. M.C. simu. stat. 0.7 − 1.3%.
Signal number: Mass pdf; moumentum scale; misalignment pdl pdf: resolution model; Hb lifetime medol; background pdf 1-6.5% Eff. Reconstruction: M.C. Truth & tag&probe corr. ~3% Eff. Trigger: M.C. Truth & tag&probe corr. ~3% Unfolding: Jpsi-> Hb
Hb production spectrum: PYTHIA 2-7% Hb->Jpsi decay spectrum: EvtGen 0.5-3% eff. For unfolding correlation: limited pT region <1%
First CMS 10pb-1 data in pT [5,40] GeV/c limited by systematic uncertainties J/ : ~10-15% inclusive b hadrons: ~15-22%
2010-04-18 ICSHEP 8, Apr. 17-19, 2010 24
CMS QTF group
2010-04-18 ICSHEP 8, Apr. 17-19, 2010 25
CMS Muon Trigger Strategy
2010-04-18 ICSHEP 8, Apr. 17-19, 2010 26
CMS pp@7TeV data: Preliminary
Fill 1005-1022 HF Vtx Totals 111.17 113.86 /ub
2010-04-18 ICSHEP 8, Apr. 17-19, 2010 27
THANKS!
2010-04-18 ICSHEP 8, Apr. 17-19, 2010 28
BACKUPS
2010-04-18 ICSHEP 8, Apr. 17-19, 2010 29
CDFII’s result
•PPbar energy: 1.96 TeV.
•Integrated luminosity: 39.7 pb-1.
•Jpsi 6.9%+(pT) Inclu b 3-13%
2010-04-18 ICSHEP 8, Apr. 17-19, 2010 30
Inv. Mass of J/ vs diff. pT bin
CDFII