Sensitivity of the LHC isolated-gamma+jet data to the parton distribution functions of the proton

TL;DR

This study evaluates how isolated-photon+jet measurements at the LHC influence our understanding of proton parton distribution functions, highlighting potential improvements with future data.

Contribution

It applies Bayesian reweighting to NLO pQCD calculations to assess the impact of gamma+jet data on proton PDFs, showing potential for enhanced constraints.

Findings

Current data provide mild constraints on PDFs.

Future measurements can significantly improve gluon density knowledge.

Low-x quark distributions could also be better constrained.

Abstract

We study the impact of differential isolated-photon+jet cross sections measured in proton-proton collisions at a center-of-mass energy of sqrt{s} = 7 TeV on the parton distribution functions (PDF) of the proton. Next-to-leading order perturbative QCD (pQCD) calculations complemented with the NNPDF2.1 parton densities, and a Bayesian PDF reweighting method are employed. We find that although the current data provide only mild constraints to the parton densities, future gamma-jet measurements with reduced experimental uncertainties can improve our knowledge of the gluon density over a wide range of parton fractional momenta x as well as of the quarks at low-x.