Abstract

The relative modification of the prompt psi(2S) and J/psi yields from pp to PbPb collisions, at the center of mass energy of 5.02 TeV per nucleon pair, is presented. The analysis is based on pp and PbPb data samples collected by the CMS experiment at the LHC in 2015, corresponding to integrated luminosities of 28.0 inverse picobarns and 464 inverse microbarns, respectively. The double ratio of measured yields of prompt charmonia reconstructed through their decays into muon pairs, (N[psi(2S)]/N[J/psi])[PbPb] / (N[psi(2S)]/N[J/psi])[pp], is determined as a function of PbPb collision centrality and charmonium transverse momentum pt, in two kinematic intervals: abs(y) < 1.6 covering 6.5 < pt < 30 GeV/c and 1.6 < abs(y) < 2.4 covering 3 < pt < 30 GeV/c. The centrality-integrated double ratios are 0.36 +/- 0.08 (stat) +/-0.05 (syst) in the first interval and 0.24 +/- 0.22 (stat) +/- 0.09 (syst) in the second. The double ratio is lower than unity in all the measured bins, suggesting that the psi(2S) yield is more suppressed than the J/psi yield in the explored phase space.

Highlights

  • The relative modification of the prompt ψð2SÞ and J=ψ yields from pp to PbPb collisions, at the centerof-mass energy of 5.02 TeV per nucleon pair, is presented

  • Quarkonium production is expected to be significantly influenced by the formation of a quark-gluon plasma (QGP) in heavy ion collisions, thereby providing an important probe of the QGP properties

  • While the earlyformed mesons propagate through the medium and probe its space-time evolution, the overall production rates can reflect later production mechanisms

Read more

Summary

Data Total fit Background

9 < pT < 12 GeV=c, all centrality, and (right) 1.6 < jyj < 2.4, 3 < pT < 30 GeV=c, 0%–20% centrality. Validated with two-dimensional fits to the dimuon mass and pseudoproper decay length distributions [25]. The PbPb event sample does not have enough ψð2SÞ events to provide a reliable two-dimensional fit. The variation in the double ratio when using nonprompt fractions from the two-dimensional fits is taken as a systematic uncertainty, never exceeding 0.07. Residual noncancellations of efficiencies in the double ratio are evaluated with MC studies, considering a broad range of pT spectra compatible with the pp and PbPb data within their uncertainties. The corresponding systematic uncertainty varies between 0.01 and 0.05, with the exception of the lowest pT bin, where it reaches 0.10. If the quarkonium acceptances were different in pp and PbPb, 162301-3

Prompt only
Findings
Measurement of and pp Collisions
Full Text
Published version (Free)

Talk to us

Join us for a 30 min session where you can share your feedback and ask us any queries you have

Schedule a call