Proton-PDF uncertainties in extracting nuclear PDFs from $W^{\pm }$ production in p+Pb collisions

Abstract

We discuss the recent CMS Collaboration measurement of $W^{\pm }$ boson production in p+Pb collisions at 8.16 TeV in terms of the constraining power on nuclear parton distribution functions (PDFs). The impact of the free-proton PDF uncertainties on the nuclear PDF extraction is quantified by using a theoretical covariance-matrix method and Hessian PDF reweighting. We discuss different ways to mitigate these theoretical uncertainties, including self-normalization, forward-to-backward ratios and nuclear-modification ratios. It is found that none of these methods offer perfect cancellation of the free-proton PDFs but, with the present data uncertainties, the residual free-proton-PDF dependence has, conveniently for the global analyses, little effect on the extraction of the nuclear modifications. Based on a simple estimate of obtainable statistics at the LHC Run 3, we argue that this will change in the near future and it becomes more important to propagate the proton-PDF uncertainties accordingly. Using the obtained information on the correlations of the free-proton uncertainties, we also identify a new charge asymmetry ratio, where the cancellation of the proton-PDF uncertainties is found to be extremely good.

15 pages, 17 figures

References in corpus (5)

• EPS09 - a New Generation of NLO and LO Nuclear Parton Distribution Functions
• Determination of nuclear parton distribution functions and their uncertainties at next-to-leading order
• Nuclear Parton Distributions from Lepton-Nucleus Scattering and the Impact of an Electron-Ion Collider
• Strange Quark PDFs and Implications for Drell-Yan Boson Production at the LHC
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Cited by in corpus (1)

• EPPS21: A global QCD analysis of nuclear PDFs