Global QCD Analysis of Parton Structure of the Nucleon: CTEQ5 Parton Distributions
H. L. Lai, J. Huston, S. Kuhlmann, J. Morfin, F. Olness, J. F. Owens, J. Pumplin, W. K. Tung
TL;DR
This work presents the CTEQ5 global QCD analysis to determine nucleon parton distributions by integrating diverse high-energy data (DIS, DY, jets) and by examining heavy-quark schemes and renormalization choices. It fixes αs(mZ)=0.118 and provides multiple PDF sets (M,D,L,HQ,F3,F4,HJ) to cover general and heavy-quark–specific applications, with jet data sharpening the gluon distribution in 0.05<x<0.25 and Drell-Yan/W asymmetries refining d/u and sea-quark behavior. The study discusses the limitations of direct-photon inputs and the impact of deuteron corrections, and it compares its PDFs with MRST to highlight scheme- and data-driven differences. Overall, the paper demonstrates strong QCD consistency across a broad data set while outlining key uncertainties and avenues for future improvement in PDF determinations.
Abstract
An up-to-date global QCD analysis of high energy lepton-hadron and hadron-hadron interactions is performed to better determine the gluon and quark parton distributions in the nucleon. Improved experimental data on inclusive jet production, in conjunction with precise deep inelastic scattering data, place good constraints on the gluon over a wide range of x; while new data on asymmetries in Drell-Yan processes contribute to better determine the d/u ratio. Comparisons with results of other recent global analyses are made, and the differences are described. Open issues and the general problem of determining the uncertainties of parton distributions are discussed.