Suppression of inclusive J/$\mathbf{\psi}$ and $\mathbf{\psi}$(2S) production in p-Pb collisions with ALICE at the LHC

TL;DR

This paper reports on the suppression of J/ψ and ψ(2S) production in proton-lead collisions at the LHC, highlighting differences between experimental results and theoretical models, especially for ψ(2S).

Contribution

It provides new measurements of nuclear modification factors for J/ψ and ψ(2S) at different rapidities and event activities in p-Pb collisions, revealing the need for additional mechanisms beyond current models.

Findings

J/ψ suppression is consistent with nuclear shadowing and energy loss models.

ψ(2S) suppression cannot be fully explained by existing models.

Different suppression patterns observed at forward and backward rapidities.

Abstract

The ALICE Collaboration has studied inclusive J/$\psi$ and $\psi$(2S) production in p-Pb collisions at $\sqrt{s_{\rm NN}} = 5.02$ TeV with the Muon Spectrometer. The measurement was performed at forward (2.03 $<$ $y_{\rm cms}$ $<$ 3.53) and backward ($-$4.46 $<$ $y_{\rm cms}$ $<$ $-$2.96) centre of mass rapidities. The nuclear modification factor of J/$\psi$ and $\psi$(2S) has been measured as a function of transverse momentum and event activity. Theoretical models based on nuclear shadowing, coherent energy loss or both are in reasonable agreement with the J/$\psi$ results but cannot describe the $\psi$(2S) behaviour. Other mechanisms must be invoked in order to explain the $\psi$(2S) suppression in p-Pb collisions.