Improved Parton Distributions from Global Analysis of Recent Deep Inelastic Scattering and Inclusive Jet Data

TL;DR

This paper integrates recent high-precision deep inelastic scattering data with Tevatron inclusive jet measurements to perform a comprehensive global QCD analysis of parton distribution functions. It explores how the gluon distribution $G(x,Q)$ is constrained, considering its strong coupling to the strong coupling $\alpha_s$ and the impact of different initial-gluon parametrizations and data selections. The authors introduce the CT EQ4 family of PDFs, including variations in $\alpha_s$, a low-$Q_0$ option, and a jet-tuned version (CTEQ4HJ) to address high-$E_T$ jet data, demonstrating that jet measurements can significantly tighten gluon uncertainties while remaining compatible with DIS constraints. The study highlights that while small-$x$ gluons are now well constrained, large-$x$ behavior remains sensitive to data and modeling, with $\alpha_s$ being the dominant source of residual uncertainty.

Abstract

The impact of recent precision measurements of DIS structure functions and inclusive jet production at the Tevatron on the global QCD analysis of parton distribution functions is studied in detail. Particular emphasis is placed on exploring the range of variation of the gluon distribution $G(x,Q)$ allowed by these new data. The strong coupling of $G(x,Q)$ with $α_s$ is fully taken into account. A new generation of CTEQ parton distributions, CTEQ4, is presented. It consists of the three standard sets (\mbox{\small {$\overline {\rm MS}$}}, {\protect \small DIS} and leading order), a series that gives a range of parton distributions with corresponding $α_s$'s, and a set with a low starting value of $Q$. Previously obtained gluon distributions that are consistent with the high $E_t$ jet cross-section are also discussed in the context of this new global analysis.