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