Nuclear parton distribution functions and their uncertainties

Abstract

We analyze experimental data of nuclear structure-function ratios $F_2^A∕F_2^{A^{\prime }}$ and Drell-Yan cross section ratios for obtaining optimum parton distribution functions (PDFs) in nuclei. Then, uncertainties of the nuclear PDFs are estimated by the Hessian method. Valence-quark distributions are determined by the $F_2$ data at large $x$; however, the small-$x$ part is not obvious from the data. On the other hand, the antiquark distributions are determined well at $x\sim 0.01$ from the $F_2$ data and at $x\sim 0.1$ by the Drell-Yan data; however, the large-$x$ behavior is not clear. Gluon distributions cannot be fixed by the present data and they have large uncertainties in the whole $x$ region. Parametrization results are shown in comparison with the data. We provide a useful code for calculating nuclear PDFs at given $x$ and $Q^2$.