# Relative Modification of Prompt ${\psi}(2S)$ and $J/{psi}$ Yields from $pp$ to PbPb Collisions at $\sqrt{{s}_{NN}}=5.02\text{ }\text{ }\mathrm{TeV}$

Sirunyan, A M; Tumasyan, A; et al; Aarrestad, T K; Amsler, C; Caminada, L; Canelli, F; De Cosa, A; Galloni, C; Hinzmann, A; Hreus, T; Kilminster, B; Ngadiuba, J; Pinna, D; Rauco, G; Robmann, P; Salerno, D; Yang, Y; Zucchetta, A; et al (2017). Relative Modification of Prompt ${\psi}(2S)$ and $J/{psi}$ Yields from $pp$ to PbPb Collisions at $\sqrt{{s}_{NN}}=5.02\text{ }\text{ }\mathrm{TeV}$. Physical Review Letters, 118(16):162301.

## 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 $28.0\text{ }\text{ }{\mathrm{pb}}^{{-}1}$ and $464\text{ }\text{ }{\mu}{\mathrm{b}}^{{-}1}$, respectively. The double ratio of measured yields of prompt charmonia reconstructed through their decays into muon pairs, $({N}_{{\psi}(2S)}/{N}_{J/{\psi}}{)}_{\mathrm{PbPb}}/({N}_{{\psi}(2S)}/{N}_{J/{\psi}}{)}_{pp}$, is determined as a function of PbPb collision centrality and charmonium transverse momentum ${p}_{T}$, in two kinematic intervals: $|y| < 1.6$ covering $6.5 < {p}_{T} < 30 {GeV} /c$ and $1.6 < |y| < 2.4$ covering $3 < {p}_{T} < 30 {GeV} /c$. The centrality-integrated double ratios are $0.36\pm{}0.08(\mathrm{stat})\pm{}0.05(\mathrm{syst})$ in the first interval and $0.24\pm{}0.22(\mathrm{stat})\pm{}0.09(\mathrm{syst})$ 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.

## 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 $28.0\text{ }\text{ }{\mathrm{pb}}^{{-}1}$ and $464\text{ }\text{ }{\mu}{\mathrm{b}}^{{-}1}$, respectively. The double ratio of measured yields of prompt charmonia reconstructed through their decays into muon pairs, $({N}_{{\psi}(2S)}/{N}_{J/{\psi}}{)}_{\mathrm{PbPb}}/({N}_{{\psi}(2S)}/{N}_{J/{\psi}}{)}_{pp}$, is determined as a function of PbPb collision centrality and charmonium transverse momentum ${p}_{T}$, in two kinematic intervals: $|y| < 1.6$ covering $6.5 < {p}_{T} < 30 {GeV} /c$ and $1.6 < |y| < 2.4$ covering $3 < {p}_{T} < 30 {GeV} /c$. The centrality-integrated double ratios are $0.36\pm{}0.08(\mathrm{stat})\pm{}0.05(\mathrm{syst})$ in the first interval and $0.24\pm{}0.22(\mathrm{stat})\pm{}0.09(\mathrm{syst})$ 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.

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