Impact of LHC vector boson production in heavy ion collisions on strange PDFs

TL;DR

This paper investigates how LHC W/Z boson production data from heavy ion collisions influences the understanding of strange quark distributions in nucleons, revealing a larger strange sea at small x than previously thought.

Contribution

It extends the nCTEQ15 nPDFs to include LHC W/Z data, providing new insights into strange quark distributions and nuclear corrections in heavy ion collisions.

Findings

The small x strange sea is larger than previously estimated.

LHC W/Z data impacts the flavor differentiation in nPDFs.

Nuclear corrections are crucial for accurate strange quark PDF extraction.

Abstract

The extraction of the strange quark parton distribution function (PDF) poses a long-standing puzzle. Measurements from neutrino-nucleus deep inelastic scattering (DIS) experiments suggest the strange quark is suppressed compared to the light sea quarks, while recent studies of W/Z boson production at the LHC imply a larger strange component at small x values. As the parton flavor determination in the proton depends on nuclear corrections, e.g. from heavy-target DIS, LHC heavy ion measurements can provide a distinct perspective to help clarify this situation. In this investigation we extend the nCTEQ15 nPDFs to study the impact of the LHC proton-lead W/Z production data on both the flavor differentiation and nuclear corrections. This complementary data set provides new insights on both the LHC W/Z proton analyses and the neutrino-nucleus DIS data. We identify these new nPDFs as nCTEQ15WZ. Our calculations are performed using a new implementation of the nCTEQ code (nCTEQ++) based on C++ which enables us to easily interface to external programs such as HOPPET, APPLgrid and MCFM. Our results indicate that, as suggested by the proton data, the small x nuclear strange sea appears larger than previously expected, even when the normalization of the W/Z data is accommodated in the fit. Extending the nCTEQ15 analysis to include LHC W/Z data represents an important step as we advance toward the next generation of nPDFs.