Dijets in p+Pb collisions and their quantitative constraints for nuclear PDFs

TL;DR

This paper analyzes high-pT dijet production in p+Pb collisions at the LHC using perturbative QCD, showing that dijet rapidity distributions are sensitive probes of nuclear gluon PDFs, especially for x>0.01.

Contribution

It demonstrates that normalized dijet rapidity distributions are robust probes of nuclear PDFs, particularly gluon densities, with better sensitivity than inclusive hadron production.

Findings

Dijet rapidity distributions are sensitive to nuclear effects.

Preliminary CMS data support gluon antishadowing in nuclear PDFs.

Next-to-leading order corrections have limited impact on normalized distributions.

Abstract

We present a perturbative QCD analysis concerning the production of high-pT dijets in p+Pb collisions at the LHC. The next-to-leading order corrections, scale variations and free-proton PDF uncertainties are found to have only a relatively small influence on the normalized dijet rapidity distributions. Interestingly, however, these novel observables prove to retain substantial sensitivity to the nuclear effects in the PDFs. Especially, they serve as a more robust probe of the nuclear gluon densities at $x>0.01$, than e.g. the inclusive hadron production. We confront our calculations with the recent data by the CMS collaboration. These preliminary data lend striking support to the gluon antishadowing similar to that in the EPS09 nuclear PDFs.