Measurement of psi(2S) nuclear modification at backward and forward rapidity in p plus p, p plus Al, and p plus Au collisions at root sNN=200 GeV

Abstract

Suppression of the J/psi 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 psi(2S) state in p + A and d + A collisions suggested the presence of final-state effects. Results of J/psi and psi(2S) measurements in the dimuon decay channel are presented here for p + p, p + Al, and p + Au collision systems at root sNN = 200 GeV. The results are predominantly shown in the form of the nuclear-modification factor, R-pA, the ratio of the psi(2S) invariant yield per nucleon-nucleon collision in collisions of proton on target nucleus to that in p + p collisions. Measurements of the J/psi and psi(2S) nuclear-modification factor are compared with shadowing and transport-model predictions, as well as to complementary measurements at Large Hadron Collider energies.