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

Abstract

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 jets P , 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 jets γ .

Photon and Pomeron-induced Production of Dijets in pp, pA and AA Collisions

“…The promising results presented in Ref. [18] motivate a more detailed analysis of the dijet production, taking into account the contribution of other processes that are characterized by the same topology. In what follows, we will estimate the dijet production in photon-photon and pomeron-pomeron interactions present in pp/ p A/A A collisions and compare the predictions with those for the dijet production in photonpomeron interactions.…”

“…In order to specify the diffractive gluon distribution for a nucleus g D A (x, μ 2 ), we will follow the approach proposed in Ref. [18] (see also Ref. [37]), which estimates g D A taking into account the nuclear effects associated with the nuclear coherence and the leading twist nuclear shadowing.…”

“…Consequently, the nuclear diffractive gluon distribution can be expressed as follows (for details see Ref. [18]):…”

“…In particular, dijet production by photon-pomeron interactions in ultraperipheral pp/ p A/A A collisions, characterized by two intact hadrons and two rapidity gaps in the final state, has been recently investigated in Ref. [18], considering the resolved pomeron model, in which the pomeron is assumed to have a partonic structure, as proposed by Ingelman and Schlein [19] many years ago. They have obtained large values for the cross sections as a function of various variables.…”

Single-diffractive Drell–Yan pair production at the LHC

“…To date, these conflicting results prevent to draw a conclusive statement a e-mail: federico.alberto.ceccopieri@cern.ch about factorisation in this case. We note, however, that the measurements of diffractive dijet photoproduction in ultraperipheral collisions in pp and p A collisions at the LHC [11] may offer an alternative way to settle this issue.…”