Quarkonia spectra in PbPb at 2.76 TeV

Abdulla Abdulsalam(Dr. Prashant Shukla)

BARC, Mumbai

Outline

•Motivation•Event selection•Kinematic cuts•Acceptance and efficiency study•Summary and plans

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Motivation

• Measurement of J/ψ→μ+μ- (BR=5.93%)

J/ψ is a powerful tool to study hot and dense matter in the collision

• Measurement of B→(BR=1.16%) J/ψ→μ+μ-

B mesons containing b quark are abundantly produced in early stages of collision, loses energy in medium and carry information about the medium properties.

• Measurement in the same kinematic space as in pp for direct comparison.

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Event Selection Minimum bias collisions L1 BscMinBiasThreshold1 (L1a36) OR L1 HcalHfCoincidencePm (L1a44) Default offline HI PAG selection Coincidence of 3 HF towers above threshold Selection of at least a two-track fitted vertex Cluster-shape filter re-run offline Reject BSC beam halo L1 technical bits Dimuon trigger HLT HIL1DoubleMuOpen Core (until run 151020) only 1Z HLT HIL2DoubleMu3 Core Statistics

eq no of MB 51,016,587/0.97 (eff) = 52,594,419

∫L = 6.88 μb -1 ( using Glauber calculation )3

The data sets and cuts

Data Set: CorePhysicsPromptRecoV3

Muon Quality Cuts: Same as used in Z0 to start with (no pT cut)

We present first quarkonia mass spectra in PbPb collision at CMS.

We fit Gaussian for invariant mass and polynomial1 & polynomial2 for fitting background

Optimisation of cuts for J/ψ study is in progress.

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Muon Quality Cuts

Triggered pT > 3 GeV/c for single muon

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J/ψ: dimuon all acceptance

yield by bin counting range =(3.0-3.2) GeV/c2

N =351.56 ± 30.57 width = 34 MeV/c2

Int.luminosity = 6.88μb-1

gaussian for invariant mass

polynomial2 for background

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J/ψ: dimuon pT > 6.5 GeV

Comparative study

with pp data dimuon pT [6.5, 30.0]

yield by bin counting range =(3.0-3.2) GeV/c2

N =253.75 ± 19.45

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J/ψ: single muon pT > 4 GeV

Comparing with pp data

pT> 4 GeV, more clean N = 136.25 ± 12.56

gaussian for invariant mass polynomial2 for background

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J/ψ: single muon |Eta| < 0.8

for barrel region most cleanest

N = 64.31 ± 8.81 width =27 MeV/c2

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Dimuon mass in pT bins

pT(6.5, 10) N = 143.98 ± 15.30 pT(10, 12) N = 50.14 ± 7.86

pT(12, 30) N = 64.95 ± 8.78 yield by bin counting

range =(3.0-3.2) GeV/c2

gaussian for invariant mass polynomail1 for background

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pT(6.5,10) pT(10,12)

pT(12,30)

Dimuon in different pT & y region

dimuon pT > 6.5 & |y| < 1.2 N = 130.24 ± 13.48

dimuon pT > 2 & 1.2 < |y|<1.6 N = 69.20 ± 12.91

dimuon 1.6 < |y| < 2.4 N = 150.28 ± 23.74 gaussian for invariant mass

Polynomial2 for background11

J/ψ :Centrality Study

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Jpsi Centrality all acceptanceCentrality [0,10]N =110.53 ± 21.90

Centrality [30,60]N =102.10 ± 11.66

Centrality [60,100]N =9.24± 3.28

Centrality [10, 30]N =123.08± 17.80

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Upsilon: single Muon pT > 4 GeV

yield by bin counting range =(9.0-10) GeV/c2

N = 54.12 ± 14.31 width = 140 MeV/c2

gaussian for invariant mass

polnomial2 for background

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Acceptance and Efficiency Study

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Input pT and rapidity distribution

pTy

pT y

J/ψ rapidity distributionfrom NLO calculation

b quark rapidity distributionfrom NLO calculation

b quark pT distributionfrom NLO calculation

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J/ψ pT distribution from NLO calculation

b quark pT distributionfrom NLO calculation

Acceptance and Efficiency

J/Ψ from B-meson can be separated by the secondary vertex information.

Reconstruction efficiency= 2.11%

J/ Ψ →μ+ μ- B→J/ Ψ→ μ+ μ-

Acceptance cuts |η| <0.8 Acceptance cuts |η| <0.8 and P

T>3

Acceptance cuts |η| <2.1Acceptance cuts |η| <2.1 and P

T>3

Acceptance cuts |η| <2.4 Acceptance cuts |η| <2.4 and P

T>3

19.02%0.373%

74.37%0.829%

84.49%0.953%

14.82%0.38%

66.8%1.1%

78.46%1.32%

J/Ψ → μ+ μ- and B→ J/Ψ→ μ+ μ- generated, reconstructed using CMSSW and calculated acceptance

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Acceptance = each single muon in|Eta|< 2.4 Generated J/Ψ signal in y| < 2.4

Summary and plans

1. Successful study of J/ψ (eta, pT and centrality) from PbPb data at 2.76 TeV.

2. We are in the process of optimising muon quality cuts for quarkonia analysis.

3. We apply secondary vertex study to separate the primary J/ψ and secondary J/ψ.

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THANK YOU

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