Multiplicity Structure of the Hadronic Final State in Diffractive Deep-Inelastic Scattering at HERA

TL;DR

This paper investigates the multiplicity structure of hadronic systems in diffractive deep-inelastic scattering at HERA, revealing insights into the production mechanism involving gluons and comparing various models to experimental data.

Contribution

It provides a detailed analysis of multiplicity distributions and correlations in diffractive DIS, and compares these with multiple theoretical models including QCD-Regge analysis.

Findings

Data suggest a production mechanism involving a mixture of partonic states and significant gluon content.

The data are well described by a QCD-Regge based model with a large gluonic component.

Soft colour interaction models also successfully describe the data.

Abstract

The multiplicity structure of the hadronic system X produced in deep-inelastic processes at HERA of the type ep -> eXY, where Y is a hadronic system with mass M_Y< 1.6 GeV and where the squared momentum transfer at the pY vertex, t, is limited to |t|<1 GeV^2, is studied as a function of the invariant mass M_X of the system X. Results are presented on multiplicity distributions and multiplicity moments, rapidity spectra and forward-backward correlations in the centre-of-mass system of X. The data are compared to results in e+e- annihilation, fixed-target lepton-nucleon collisions, hadro-produced diffractive final states and to non-diffractive hadron-hadron collisions. The comparison suggests a production mechanism of virtual photon dissociation which involves a mixture of partonic states and a significant gluon content. The data are well described by a model, based on a QCD-Regge analysis of the diffractive structure function, which assumes a large hard gluonic component of the colourless exchange at low Q^2. A model with soft colour interactions is also successful.