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Measurement of prompt and nonprompt J/psi production in pp and pPb collisions at sqrt(s[NN]) = 5.02 TeV

5.02 TeV 양성자-양성자, 양성자-납핵 충돌에서 J/psi 중간자 생성에 대한 연구

초록/요약

The measurement of J/psi meson production in proton-proton (pp) and proton-lead (pPb) collisions at a center-of-mass energy per nucleon pair of 5.02 TeV by the CMS experiment at the CERN LHC is reported. The data samples used in the analysis correspond to integrated luminosities of 28 pb^{-1} and 35 nb^{-1} for pp and pPb collisions, respectively. Prompt and nonprompt J/psi mesons, the latter produced in the decay of B hadrons, are measured in their dimuon decay channels. Differential cross sections are measured in the transverse momentum range of 2 < p_{T} < 30 GeV/c, and center-of-mass rapidity ranges of |y_{CM}| < 2.4 (pp) and 2.87 < y_{CM} < 1.93 (pPb). The nuclear modification factor, R_{pPb}, is measured as functions of both p_{T} and y_{CM}. Small modifications to the J/psi cross sections are observed in pPb relative to pp collisions. The ratio of J/psi production cross sections in p-going and Pb-going directions, R_{FB}, studied as functions of p_{T} and y_{CM}, shows a significant decrease for increasing transverse energy deposited at large pseudorapidities. These results, which cover a wide kinematic range, provide new insight on the role of cold nuclear matter effects on prompt and nonprompt J/psi productions.

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목차

1 Introduction
2 Theoretical framework
2.1 Elementary particles and interactions
2.1.1 Standard Model
2.1.2 Quantum chromodynamics
2.2 Heavy-flavor hadrons
2.2.1 Open-heavy flavor production
2.2.2 Quarkonium production
2.2.3 Characteristics of J/psi mesons
2.3 Cold nuclear matter effects
2.3.1 Nuclear parton distribution function
2.3.2 Gluon saturation at low x
2.3.3 Initial and final state energy loss
2.3.4 Nuclear absorption
2.3.5 Comover breakup
3 Experimental setup
3.1 Large Hadron Collider (LHC)
3.2 Compact Muon Solenoid (CMS)
3.2.1 Conventions
3.2.2 Inner tracking system
3.2.3 Electromagnetic calorimeter
3.2.4 Hadron calorimeter
3.2.5 Muon system
3.3 Trigger
3.3.1 Data acquisition system
3.3.2 Level 1 trigger
3.3.3 High level trigger
3.3.4 Muon trigger
3.4 Offline reconstruction
3.4.1 Track reconstruction
3.4.2 Vertex reconstruction
3.4.3 Tracker muon
3.4.4 Global muon
4 Analysis procedure
4.1 Samples and selection
4.1.1 Data sets
4.1.2 Background-event suppression and pileup rejection
4.1.3 Monte-Carlo simulation
4.1.4 Muon selection
4.2 Signal extraction
4.2.1 Analysis binning
4.2.2 InclusiveJ/psi mesons
4.2.3 Separation of prompt and nonprompt J/psi mesons
4.2.4 Systematic uncertainties
4.3 Acceptance correction
4.3.1 Definition
4.3.2 Reweighting of the p_{T} spectra in MC samples
4.3.3 Systematic uncertainties
4.4 Efficiency correction
4.4.1 Dimuon efficiency from MC simulation
4.4.2 Secondary correction: tag-and-probe
4.4.3 Systematic uncertainties
4.5 Summary for corrections and systematic uncertainties
4.5.1 Final correction factors (Acc e)
4.5.2 Total systematic uncertainties
5 Results
5.1 Definitions: differential cross section, R_{pPb}, and R_{FB}
5.2 Prompt J/psi mesons
5.3 Nonprompt J/psi mesons
5.4 Comparisons
5.4.1 Theoretical calculations
5.4.2 Other experiments
6 Summary and conclusion

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