Determination of nuclear parton distribution functions and their uncertainties at next-to-leading order

Abstract

Nuclear parton distribution functions (NPDFs) are determined by global analyses of experimental data on structure-function ratios F A 2 /F A 2 and Drell-Yan cross-section ratios σ A DY /σ A DY . The analyses are done in the leading order (LO) and next-to-leading order (NLO) of running coupling constant α s . Uncertainties of the NPDFs are estimated in both LO and NLO for finding possible NLO improvement. Valence-quark distributions are well determined, and antiquark distributions are also determined at x < 0.1. However, the antiquark distributions have large uncertainties at x > 0.2. Gluon modifications cannot be fixed at this stage. Although the advantage of the NLO analysis, in comparison with the LO one, is generally the sensitivity to the gluon distributions, gluon uncertainties are almost the same in the LO and NLO. It is because current scaling-violation data are not accurate enough to determine precise nuclear gluon distributions. Modifications of the PDFs in the deuteron are also discussed by including data on the proton-deuteron ratio F D 2 /F p 2 in the analysis. A code is provided for calculating the NPDFs and their uncertainties at given x and Q 2 in the LO and NLO.

Constraining gluon shadowing using photoproduction in ultraperipheralpAandAAcollisions

“…The issue of uncertainties in parton distributions is becoming increasingly important especially in relation to precision tests of QCD. Discussions on uncertainties in nuclear parton distributions can be found in [46,48].…”

“…Two sets are by Eskola, Paukunnen, and Salgado, namely EPS08 and EPS09 [47,48]. The third is the Hirai-Kumano-Nagai (HKN07) distributions [46]. While EPS08 is only to leading order (LO), both EPS09 and HKN07 are available up to next-to-leading order (NLO).…”

“…around their initial starting scales) since evolution to high Q 2 tends to lessen the differences. Earlier global analyses [43][44][45][46] relied heavily on fixed-target nuclear deep-inelastic scattering (DIS) and Drell-Yan (DY) lepton-pair production. Incorporation of data on inclusive hadron production in deuteron-gold collisions has been implemented in [47,48], and neutrino-iron data in [49][50][51].…”

“…This relevant for the dominant direct contribution in photoproduction of heavy quarks and elastic production of vector mesons. Both HKN07 [46] and EPS09 [48] have facilities for estimating error in the determination of a nPDs-dependent quantity like the cross section due to the uncertainties in the nuclear parton distributions. The HKN07 set achieves this through the availability of a set of gradient functions while EPS09 has thirty error sets to be used in conjunction with free proton parton distributions error sets.…”

Measurement of the D0 Meson Production in Pb–Pb and p–Pb Collisions

“…In [74], it was shown that a Langevin-based heavy quark transport model can qualitatively explain the large suppression (and azimuthal anisotropy) of electrons from heavy flavor decays in Au+Au collisions. The model places a heavy quark into a thermal medium, and assumes that the interaction of the heavy quark with the medium can be described by uncorrelated momentum kicks.…”