Measurement of prompt and nonprompt charmonium suppression in PbPb collisions at 5.02 TeV

TL;DR

This study measures the suppression of prompt and nonprompt charmonium states in lead-lead collisions at 5.02 TeV, revealing increased suppression with centrality and differences between states, providing insights into quark-gluon plasma effects.

Contribution

First measurement of prompt and nonprompt charmonium suppression at 5.02 TeV in PbPb collisions, comparing with previous energies and analyzing dependencies on centrality, rapidity, and transverse momentum.

Findings

Suppression increases with collision centrality.

No rapidity dependence observed for suppression.

Prompt ψ(2S) more suppressed than J/ψ across all pT.

Abstract

The nuclear modification factors of J/$\psi$ and $\psi$(2S) mesons are measured in PbPb collisions at a centre-of-mass energy per nucleon pair of $\sqrt{s_{\mathrm{NN}}} =$ 5.02 TeV. The analysis is based on PbPb and pp data samples collected by CMS at the LHC in 2015, corresponding to integrated luminosities of 464 $\mu$b$^{-1}$ and 28 pb$^{-1}$, respectively. The measurements are performed in the dimuon rapidity range of $|y| <$ 2.4 as a function of centrality, rapidity, and transverse momentum (p$_\mathrm{T}$) from p$_\mathrm{T}=$ 3 GeV/$c$ in the most forward region and up to 50 GeV/$c$. Both prompt and nonprompt (coming from b hadron decays) mesons are observed to be increasingly suppressed with centrality, with a magnitude similar to the one observed at $\sqrt{s_{\mathrm{NN}}}=$ 2.76 TeV for the two J/$\psi$ meson components. No dependence on rapidity is observed for either prompt or nonprompt J/$\psi$ mesons. An indication of a lower prompt J/$\psi$ meson suppression at p$_\mathrm{T} >$ 25 GeV/$c$ is seen with respect to that observed at intermediate p$_\mathrm{T}$. The prompt $\psi$(2S) meson yield is found to be more suppressed than that of the prompt J/$\psi$ mesons in the entire p$_\mathrm{T}$ range.