TUJU21: nuclear PDFs with electroweak-boson data at NNLO

TL;DR

This paper updates nuclear parton distribution functions by incorporating recent electroweak-boson data from LHC at NNLO, improving the accuracy and kinematic coverage of nPDFs.

Contribution

It introduces the first NNLO nPDF analysis including LHC electroweak-boson data, enhancing previous models with new experimental constraints.

Findings

NNLO analysis yields a better fit with lower chi-squared value.

Inclusion of LHC data extends the kinematic range of nPDFs.

NNLO corrections are significant for electroweak-boson production predictions.

Abstract

Nuclear parton distribution functions (nPDFs) can be determined in a global QCD analysis using a wide range of experimental data. In addition to older fixed-target deep inelastic scattering and Drell-Yan (DY) dilepton production data, several analyses from p+Pb collisions at the LHC provide further constraints and extend the kinematic reach of applicable data. Here we present an update of our previous TUJU19 analysis where we now include also electroweak-boson production data recently measured by ATLAS and CMS. For the first time, LHC data are included in a nPDF analysis performed at next-to-next-to-leading order (NNLO) in perturbative QCD. As before, our setup is based on the open-source analysis framework xFitter and we fit our own proton baseline, ensuring a fully consistent setup. We find good agreement with the applied data and that the resulting $\chi^2/N_{\mathrm{df}}$ is significantly smaller in case of the NNLO analysis (0.84) compared to our NLO analysis (0.94). Also, we present comparisons between our NNLO calculations and electroweak-boson production data in Pb+Pb collisions from ATLAS and CMS and DY data recently measured by CMS where NNLO corrections are found significant.