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

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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

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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

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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

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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

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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

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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

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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

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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

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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

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Mass & ppdl fitting: resol. Model Sum08

Mass: 3Gaussion Pdl: 2Gaussion

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b ctau at Gen

Ctau_b: 467 micron

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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)

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Fit results: Jpsi Pt bins 5-6, 30-40GeV/c

p-jpsi: 1060 b: 762

p-jpsi: 15126 b: 1801

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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

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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)

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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

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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

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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

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Unfolding correlation Matrix

/ _ [5,40]( )

( )

b J psi pT bGen T

Unfolding total bGen T

N p

N p

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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

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Hb production x-section@pp 10TeV

GenGen+filter

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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%

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CMS QTF group

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CMS Muon Trigger Strategy

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CMS pp@7TeV data: Preliminary

Fill 1005-1022 HF Vtx Totals 111.17 113.86 /ub

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THANKS!

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BACKUPS

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CDFII’s result

•PPbar energy: 1.96 TeV.

•Integrated luminosity: 39.7 pb-1.

•Jpsi 6.9%+(pT) Inclu b 3-13%

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Inv. Mass of J/ vs diff. pT bin

CDFII