EPPS16: Nuclear parton distributions with LHC data

TL;DR

EPPS16 presents an advanced global analysis of nuclear parton distribution functions incorporating LHC data, significantly improving flavor dependence understanding and uncertainty estimates for high-energy nuclear collision applications.

Contribution

This work introduces the first inclusion of LHC proton-lead collision data into nuclear PDF analysis, expanding data variety and allowing more flexible flavor-dependent nuclear effects.

Findings

LHC data extend the kinematic reach of nuclear PDFs.

Neutrino DIS data improve up and down valence quark behavior.

LHC dijet data constrain gluon distributions at high momentum.

Abstract

We introduce a global analysis of collinearly factorized nuclear parton distribution functions (PDFs) including, for the first time, data constraints from LHC proton-lead collisions. In comparison to our previous analysis, EPS09, where data only from charged-lepton-nucleus deep inelastic scattering (DIS), Drell-Yan (DY) dilepton production in proton-nucleus collisions and inclusive pion production in deuteron-nucleus collisions were the input, we now increase the variety of data constraints to cover also neutrino-nucleus DIS and low-mass DY production in pion-nucleus collisions. The new LHC data significantly extend the kinematic reach of the data constraints. We now allow much more freedom for the flavour dependence of nuclear effects than in other currently available analyses. As a result, especially the uncertainty estimates are more objective flavour by flavour. The neutrino DIS plays a pivotal role in obtaining a mutually consistent behaviour for both up and down valence quarks, and the LHC dijet data clearly constrain gluons at large momentum fraction. Mainly for insufficient statistics, the pion-nucleus DY and heavy gauge boson production in proton-lead collisions impose less visible constraints. The outcome - a new set of next-to-leading order nuclear PDFs called EPPS16 - is made available for applications in high-energy nuclear collisions.