Deuterium scattering experiments in CTEQ global QCD analyses: a comparative investigation

Abstract

Experimental measurements in deep-inelastic scattering and lepton-pair production on deuterium targets play an important role in the flavor separation of u and d (anti)quarks in global QCD analyses of the parton distribution functions (PDFs) of the nucleon. We investigate the impact of theoretical corrections accounting for the light-nuclear structure of the deuteron upon the fitted u, d-quark, gluon, and other PDFs in the CJ15 and CT18 families of next-to-leading order CTEQ global analyses. The investigation is done using the $$L_2$$ L 2 sensitivity statistical method, which provides a common metric to quantify the strength of experimental constraints on various PDFs and ratios of PDFs in the two distinct fitting frameworks. Using the $$L_2$$ L 2 sensitivity and other approaches, we examine the compatibility of deuteron data sets with other fitted experiments under varied implementations of the deuteron corrections. We find that freely-fitted deuteron corrections modify the PDF uncertainty at large momentum fractions and will be relevant for future PDFs affecting electroweak precision measurements.

The PDF4LHC21 combination of global PDF fits for the LHC Run III

“…DIS cross sections on iron (CCFR, CDHSW, and NuTeV) and proton-copper Drell-Yan (E605) data are corrected to the corresponding cross sections on deuterium using a phenomenological parametrization of the nuclear-to-deuteron cross section ratios. This model is acceptable with the present accuracy of data [85].…”

“…2.1, and is particularly helpful in identifying the experiments with the strongest pulls in some x regions. A comparative study of the CT and CJ PDFs [85] demonstrated that the L 2 sensitivities provide an easy-to-implement metric for apples-to-apples comparisons of the fits by different groups. In this publication, for the first time we compared the L 2 sensitivities in the CT and MSHT reduced fits.…”

EPPS21: A global QCD analysis of nuclear PDFs

“…The nuclear effects in deuteron are expected to be below 2% [38]. However, these deuteron data are already included in the CT18 fit [22] of the free proton PDFs (our baseline) neglecting the deuteron nuclear corrections [39]. Using CT18 for deuteron (with no additional corrections) thus effectively accounts also for the deuteron nuclear effects.…”

Extraction of the higher-twist parton distribution $e(x)$ from CLAS data

“…In view of these future developments, we would like to raise the question about the role of the unpolarized PDFs that contribute to the multiplicities (denominators). Appreciable conceptual and numerical differences are found for such PDFs extracted more or less stringent cuts in W and Q 2 [58]. Twist expansion of observables suggest that all-purpose global PDFs, extracted from high-energy experiments, should be used.…”