Relative modification of prompt psi(2S) and J/psi yields from pp to PbPb collisions at sqrt(s[NN]) = 5.02 TeV

TL;DR

This study measures the relative suppression of prompt psi(2S) and J/psi mesons in PbPb collisions compared to pp collisions at 5.02 TeV, revealing greater suppression of psi(2S) across various conditions.

Contribution

It provides the first detailed measurement of the double ratio of prompt psi(2S) to J/psi yields in PbPb versus pp collisions at 5.02 TeV, across different centralities and transverse momenta.

Findings

Double ratio of prompt charmonia yields is below unity in all measured bins.

Psi(2S) exhibits greater suppression than J/psi in PbPb collisions.

Results suggest significant quark-gluon plasma effects on charmonium states.

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.