Measurement of $\ensuremath{\psi}(2S)$ nuclear modification at backward and forward rapidity in $p+p,$ $p+\mathrm{Al}$, and $p+\mathrm{Au}$ collisions at $\sqrt{{s}_{NN}}=200 \mathrm{GeV}$

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Measurement of $ψ (2 S)$ nuclear modification at backward and forward rapidity in $p + p,$ $p + Al$ , and $p + Au$ collisions at $\sqrt{s_{N N}} = 200 GeV$

U. A. Acharya et al. (PHENIX Collaboration )

Phys. Rev. C 105, 064912 – Published 29 June 2022

Abstract

Suppression of the $J / ψ$ nuclear-modification factor has been seen as a trademark signature of final-state effects in large collision systems for decades. In small systems, the nuclear modification was attributed to cold-nuclear-matter effects until the observation of strong differential suppression of the $ψ (2 S)$ state in $p + A$ and $d + A$ collisions suggested the presence of final-state effects. Results of $J / ψ$ and $ψ (2 S)$ measurements in the dimuon decay channel are presented here for $p + p$ , $p + Al$ , and $p + Au$ collision systems at $\sqrt{s_{N N}} = 200 GeV$ . The results are predominantly shown in the form of the nuclear-modification factor, $R_{p A}$ , the ratio of the $ψ (2 S)$ invariant yield per nucleon-nucleon collision in collisions of proton on target nucleus to that in $p + p$ collisions. Measurements of the $J / ψ$ and $ψ (2 S)$ nuclear-modification factor are compared with shadowing and transport-model predictions, as well as to complementary measurements at Large Hadron Collider energies.