Energy dependence of J/psi absorption in proton-nucleus collisions

TL;DR

This study investigates how the absorption of J/psi particles in proton-nucleus collisions varies with energy and kinematics, providing insights crucial for interpreting signals of quark-gluon plasma formation in heavy-ion collisions.

Contribution

It offers a detailed analysis of the energy dependence of J/psi absorption using Glauber formalism and various parton distribution functions across a wide energy range.

Findings

Absorption cross section depends significantly on collision energy and J/psi kinematics.

Extrapolated absorption levels at SPS energies inform heavy-ion collision interpretations.

Results highlight the importance of energy-dependent nuclear effects in charmonium suppression studies.

Abstract

Charmonium states are expected to be considerably suppressed in the case of quark-gluon plasma formation in high-energy heavy-ion collisions. However, a robust identification of suppression patterns as signatures of a deconfined QCD medium requires a detailed understanding of the "normal nuclear absorption" already present in proton-nucleus collisions, where the charmonium production cross sections increase less than linearly with the number of target nucleons. We analyse the J/psi production cross sections measured in proton-nucleus collisions in fixed target experiments, with proton beam energies from 200 to 920 GeV, and in d-Au collisions at RHIC, at sqrt(s)=200 GeV, in the framework of the Glauber formalism, using several sets of parton distributions with and without nuclear modifications. The results reveal a significant dependence of the "absorption cross section" on the kinematics of the J/psi and on the collision energy. Extrapolating the observed patterns we derive the level of absorption expected at Elab=158 GeV, the energy at which the heavy-ion data sets were collected at the CERN SPS.