European Physical Journal C: Particles and Fields (Oct 2020)

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

  • A. Kusina,
  • T. Ježo,
  • D. B. Clark,
  • P. Duwentäster,
  • E. Godat,
  • T. J. Hobbs,
  • J. Kent,
  • M. Klasen,
  • K. Kovařík,
  • F. Lyonnet,
  • K. F. Muzakka,
  • F. I. Olness,
  • I. Schienbein,
  • J. Y. Yu

DOI
https://doi.org/10.1140/epjc/s10052-020-08532-4
Journal volume & issue
Vol. 80, no. 10
pp. 1 – 21

Abstract

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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 $$W^\pm /Z$$ 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 $$W^\pm /Z$$ W ± / Z production data on both the flavor differentiation and nuclear corrections. This complementary data set provides new insights on both the LHC $$W^\pm /Z$$ 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 $$W^{\pm }/Z$$ W ± / Z data is accommodated in the fit. Extending the nCTEQ15 analysis to include LHC $$W^\pm /Z$$ W ± / Z data represents an important step as we advance toward the next generation of nPDFs.