Cold Nuclear Matter Effects on J/psi and Upsilon Production at the LHC

TL;DR

This paper investigates cold nuclear matter effects, specifically nuclear absorption and shadowing, on J/psi and Upsilon production at the LHC, crucial for interpreting quarkonium suppression in heavy-ion collisions.

Contribution

It characterizes and analyzes the energy, rapidity, and impact-parameter dependence of shadowing and nuclear absorption effects on quarkonium production.

Findings

Shadowing varies with energy and rapidity.

Nuclear absorption impacts quarkonium yields.

Cold nuclear matter effects must be understood for QGP signals.

Abstract

The charmonium yields are expected to be considerably suppressed if a deconfined medium is formed in high-energy heavy-ion collisions. In addition, the bottomonium states, with the possible exception of the Upsilon(1S) state, are also expected to be suppressed in heavy-ion collisions. However, in proton-nucleus collisions the quarkonium production cross sections, even those of the Upsilon(1S), are also suppressed. These "cold nuclear matter" effects need to be accounted for before signals of the high density QCD medium can be identified in the measurements made in nucleus-nucleus collisions. We identify two cold nuclear matter effects important for midrapidity quarkonium production: "nuclear absorption", typically characterized as a final-state effect on the produced quarkonium state and shadowing, the modification of the parton densities in nuclei relative to the nucleon, an initial-state effect. We characterize these effects and study the energy, rapidity, and impact-parameter dependence of initial-state shadowing in this paper.