Diffractive dijet photoproduction in ultraperipheral collisions at the LHC in next-to-leading order QCD

TL;DR

This paper predicts cross sections for diffractive dijet photoproduction in ultraperipheral collisions at the LHC using next-to-leading order QCD, highlighting their potential to probe small momentum fractions and diffractive factorization breaking.

Contribution

It provides the first detailed NLO QCD predictions for diffractive dijet photoproduction in various ultraperipheral collision systems at the LHC, exploring factorization breaking scenarios.

Findings

Cross sections are large enough for experimental observation.

Enhanced sensitivity to small momentum fractions compared to HERA.

Distinguishable nuclear dependence for different factorization breaking models.

Abstract

We make predictions for the cross sections of diffractive dijet photoproduction in $pp$, $pA$ and $AA$ ultraperipheral collisions (UPCs) at the LHC during Runs 1 and 2 using next-to-leading perturbative QCD. We find that the resulting cross sections are sufficiently large and, compared to lepton-proton scattering at HERA, have an enhanced sensitivity to small observed momentum fractions in the diffractive exchange, commonly denoted $z_{P}^{\rm jets}$, and an unprecedented reach in the invariant mass of the photon-nucleon system $W$. We examine two competing schemes of diffractive QCD factorization breaking, which assume either a global suppression factor or a suppression for resolved photons only and demonstrate that the two scenarios can be distinguished by the nuclear dependence of the distributions in the observed parton momentum fraction in the photon $x_{\gamma}^{\rm jets}$.