Diffractive dijet production at HERA

TL;DR

This paper studies diffractive dijet production at HERA across various interaction regimes, comparing experimental data with theoretical models, and investigates the validity of diffractive factorisation in these processes.

Contribution

It provides detailed measurements of diffractive dijet cross sections and tests the applicability of factorisable diffractive exchange models against experimental data.

Findings

Models with gluon-dominated diffractive exchange fit the data well.

Exclusive qqbar production is a small part of the total cross section.

Data suggests possible breaking of diffractive factorisation in resolved photoproduction.

Abstract

Interactions of the type ep -> eXY are studied, where the component X of the hadronic final state contains two jets and is well separated in rapidity from a leading baryonic system Y. Analyses are performed of both resolved and direct photoproduction and of deep-inelastic scattering with photon virtualities in the range 7.5 < Q^2 < 80 GeV^2. Cross sections are presented where Y has mass M_Y < 1.6 GeV, the squared four-momentum transferred at the proton vertex satisfies |t| < 1 GeV^2 and the two jets each have transverse momentum p^jet_T > 5 GeV relative to the photon direction in the rest frame of X. Models based on a factorisable diffractive exchange with a gluon dominated structure, evolved to a scale set by the transverse momentum p^hat_T of the outgoing partons from the hard interaction, give good descriptions of the data. Exclusive qqbar production, as calculated in perturbative QCD using the squared proton gluon density, represents at most a small fraction of the measured cross section. The compatibility of the data with a breaking of diffractive factorisation due to spectator interactions in resolved photoproduction is investigated.