Global NLO Analysis of Nuclear Parton Distribution Functions

Nuclear parton distribution functions (NPDFs) are determined by a global analysis of experimental measurements on structure‐function ratios $F2A/F2A′$ and Drell‐Yan cross section ratios $σDYA/σDYA′,$ 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 $αs.$ 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.