# Nuclear Uncertainties in the Determination of Proton PDFs

## TL;DR

This paper investigates how nuclear effects introduce uncertainties in proton PDFs and finds that these uncertainties are small and have negligible impact on key distributions like the / ratio and strange quark distributions.

## Contribution

It demonstrates a method to incorporate nuclear uncertainties into global proton PDF fits and assesses their impact on key distributions.

## Key findings

- Nuclear effects cause small uncertainties in proton PDFs.
- Impact on / ratio and strange distributions is negligible.
- Nuclear uncertainties do not significantly alter the PDF fits.

## Abstract

We show how theoretical uncertainties due to nuclear effects may be incorporated into global fits of proton parton distribution functions (PDFs) that include deep-inelastic scattering and Drell-Yan data on nuclear targets. We specifically consider the CHORUS, NuTeV and E605 data included in the NNPDF3.1 fit, which used Pb, Fe and Cu targets, respectively. We show that the additional uncertainty in the proton PDFs due to nuclear effects is small, as expected, and in particular that the effect on the $\bar{d}/\bar{u}$ ratio, the total strangeness $s+\bar{s}$, and the strange valence distribution $s-\bar{s}$ is negligible.