Inclusive Diffraction at HERA

TL;DR

This paper reports on measurements of inclusive diffractive DIS cross sections at HERA, extracting and testing diffractive parton density functions through QCD fits, and comparing predictions with dijet data in DIS and photoproduction.

Contribution

It introduces a new set of diffractive parton density functions constrained by combined QCD fits to inclusive and dijet data, improving understanding of diffraction at HERA.

Findings

Good agreement between H1 and Zeus measurements.

Enhanced constraints on the diffractive gluon distribution.

Validation of factorisation assumptions in diffractive processes.

Abstract

The H1 and Zeus collaborations have measured the inclusive diffractive DIS cross section ep -> eXp and these measurements are in good agreement within a normalisation uncertainty. Diffractive parton density functions (DPDFs) have been extracted from NLO QCD fits to inclusive measurements of diffractive DIS and the predictions of these DPDFs are compared with measurements of diffractive dijets in DIS, testing the validity of the factorisation approximations used in their extraction. H1 then use these diffractive dijets in DIS data to provide further constraints in a combined QCD fit, resulting in the next generation of DPDFs which have constrained the diffractive gluon at large momentum fractions. Finally, the predictions of DPDFs are compared to diffractive dijets in photoproduction where the issue of survival probability in a hadron-hadron environment can be studied.