Global NLO Analysis of Nuclear Parton Distribution Functions

TL;DR

This paper presents a comprehensive global analysis of nuclear parton distribution functions (NPDFs) at LO and NLO, highlighting the current uncertainties and the relative precision of valence-quark versus gluon and antiquark distributions.

Contribution

It provides the first combined NLO analysis of NPDFs using a broad set of experimental data and estimates uncertainties with the Hessian method.

Findings

Valence-quark distributions are well constrained.

Antiquark and gluon distributions have large uncertainties.

NLO uncertainties are slightly smaller than LO, but less so than in nucleonic PDFs.

Abstract

Nuclear parton distribution functions (NPDFs) are determined by a global analysis of experimental measurements on structure-function ratios F_2^A/F_2^{A'} and Drell-Yan cross section ratios \sigma_{DY}^A/\sigma_{DY}^{A'}, and their uncertainties are estimated by the Hessian method. The NPDFs are obtained in both leading order (LO) and next-to-leading order (NLO) of \alpha_s. As a result, valence-quark distributions are relatively well determined, whereas antiquark distributions at x>0.2 and gluon distributions in the whole x region have large uncertainties. The NLO uncertainties are slightly smaller than the LO ones; however, such a NLO improvement is not as significant as the nucleonic case.