EPPS21: A global QCD analysis of nuclear PDFs

Eskola, Kari J.; Paakkinen, Petja; Paukkunen, Hannu; Salgado, Carlos A.

doi:10.48550/arxiv.2112.12462

Cited by 8 publications

(28 citation statements)

References 86 publications

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“…In the case of the sea quark PDFs, the enhanced shadowing for x ∼ < 10 −3 and the corresponding uncertainty reduction is qualitatively similar to that observed at the lead PDF level. The preference of the LHCb D-meson production measurements for a strong small-x shadowing of the quark and gluon PDFs of lead is in agreement with related studies of the same process in the literature [86,97,98].…”

Section: The Nnnpdf30 Determinationsupporting

confidence: 90%

“…Several groups have presented determinations of nuclear PDFs [25,32,33,97,[124][125][126][127][128][129][130][131][132], which differ in terms of the input dataset, fitting methodology, and/or theoretical settings. Here we compare the nNNPDF3.0 results with two other recent nuclear PDF analyses 2 based on global datasets, namely EPPS16 [32] and nCTEQ15WZ+SIH [33].…”

Section: Comparison With Other Global Npdf Analysesmentioning

confidence: 99%

“…While the new EPPS21 set has been presented in[97], the corresponding LHAPDF grids are not yet publicly available.…”

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confidence: 99%

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NNNPDF3.0: Evidence for a modified partonic structure in heavy nuclei

Khalek¹,

Gauld²,

Giani³

et al. 2022

Preprint

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We present an updated determination of nuclear parton distributions (nPDFs) from a global NLO QCD analysis of hard processes in fixed-target lepton-nucleus and proton-nucleus together with collider protonnucleus experiments. In addition to neutral-and charged-current deep-inelastic and Drell-Yan measurements on nuclear targets, we consider the information provided by the production of electroweak gauge bosons, isolated photons, jet pairs, and charmed mesons in proton-lead collisions at the LHC across centre-ofmass energies of 5.02 TeV (Run I) and 8.16 TeV (Run II). For the first time in a global nPDF analysis, the constraints from these various processes are accounted for both in the nuclear PDFs and in the freeproton PDF baseline. The extensive dataset underlying the nNNPDF3.0 determination, combined with its model-independent parametrisation, reveals strong evidence for nuclear-induced modifications of the partonic structure of heavy nuclei, specifically for the small-x shadowing of gluons and sea quarks, as well as the large-x anti-shadowing of gluons. As a representative phenomenological application, we provide predictions for ultra-high-energy neutrino-nucleon cross-sections, relevant for data interpretation at neutrino observatories. Our results provide key input for ongoing and future experimental programs, from that of heavy-ion collisions in controlled collider environments to the study of high-energy astrophysical processes.

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Section: The Nnnpdf30 Determinationsupporting

confidence: 90%

Section: Comparison With Other Global Npdf Analysesmentioning

confidence: 99%

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NNNPDF3.0: Evidence for a modified partonic structure in heavy nuclei

Khalek¹,

Gauld²,

Giani³

et al. 2022

Preprint

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“…The simple reweighting study performed here falls short in few aspects which we address in a concurrent global analysis [7] (see also the work in Refs. [13,14]): First, to reliably quantify the full free-proton-PDF dependence of the nuclear modifications, it is necessary to include them in all the relevant fitted observables.…”

Section: Summary and Discussionmentioning

confidence: 99%

“…One could then envisage two systematic approaches to treat the proton-PDF uncertainties in the nuclear-PDF analyses: First, one can try to reduce the proton-PDF uncertainties by using observables where one probes instead the nuclear modifications of the PDFs, which are then parametrized and fitted, and the "baseline" freeproton PDF dependence effectively drops out, as has been done systematically in the EKS-EPPS line of analyses [1,2,3,4,5,6,7], and by others [8,9,10,11,12]. This approach has been particularly attractive since much of the older DIS and DY data are in any case available only in terms of nuclear ratios.…”

Section: Introductionmentioning

confidence: 99%

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

Eskola,

Paakkinen,

Paukkunen

et al. 2022

Preprint

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We discuss the recent CMS Collaboration measurement of W ± 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-tobackward 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.

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Inclusive and diffractive dijet photoproduction in ultraperipheral heavy ion collisions at the LHC

Guzey

Klasen

2022

SciPost Phys. Proc.

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We calculate the cross section of inclusive dijet photoproduction in ultraperipheral collisions (UPCs) of heavy ions at the CERN Large Hadron Collider using next-to-leading order perturbative QCD and demonstrate that it provides a good description of the ATLAS data. We study the role of this data in constraining nuclear parton distribution functions (nPDFs) using the Bayesian reweighting technique and find that it can reduce current uncertainties of nPDFs at small x by a factor of 2. We also make predictions for diffractive dijet photoproduction in UPCs and examine its potential to shed light on the disputed mechanism of QCD factorization breaking in diffraction.

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EPPS21: A global QCD analysis of nuclear PDFs

Cited by 8 publications

References 86 publications

NNNPDF3.0: Evidence for a modified partonic structure in heavy nuclei

NNNPDF3.0: Evidence for a modified partonic structure in heavy nuclei

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

Inclusive and diffractive dijet photoproduction in ultraperipheral heavy ion collisions at the LHC

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