Constraints on nuclear gluon densities from J/psi data

TL;DR

This paper demonstrates that J/psi production data from proton-nucleus collisions at 38.8 GeV provide important constraints on the nuclear gluon density, especially in the x=0.02-0.1 range, favoring certain gluon distribution models.

Contribution

It highlights the use of J/psi production measurements to better constrain nuclear gluon densities, which are poorly determined by existing data.

Findings

J/psi data favor mild x-dependence of G^W/G^Be ratio

Supports DS and HKM gluon distribution sets

Disfavors models with large shadowing and anti-shadowing

Abstract

The gluon density in nuclei, G^A(x), is poorly constrained at all x from the current DIS and Drell-Yan data. In this paper, we point out that J/psi production measured in proton-nucleus collisions at sqrt(s)=38.8 GeV by the E866 collaboration puts stringent constraints on the x-dependence of the G^W/G^Be ratio in the x=0.02-0.1 range. The E866 data suggest a rather mild x-dependence of G^W/G^Be, and consequently tend to favour DS and HKM sets, rather than the DSg, EKS, and EPS parametrizations which exhibit a large shadowing and anti-shadowing.