Event Shape Analysis of Deep Inelastic Scattering Events with a Large Rapidity Gap at HERA

TL;DR

This paper analyzes the shape of multihadronic final states in deep inelastic scattering events with large rapidity gaps at HERA, revealing how event shapes depend on the hadronic mass and comparing results with diffractive models.

Contribution

It provides a detailed event shape analysis in the gamma*-pomeron rest frame, highlighting the need for a significant gluon component in diffractive models.

Findings

Final states become more collimated and planar with increasing M_X.

Data broadening effects suggest a significant gluon component in the pomeron.

Results support models with gluon-rich pomeron contributions.

Abstract

A global event shape analysis of the multihadronic final states observed in neutral current deep inelastic scattering events with a large rapidity gap with respect to the proton direction is presented. The analysis is performed in the range $5 \leq Q^2 \leq 185\gev^2$ and $160 \leq W \leq 250\gev$, where $Q^2$ is the virtuality of the photon and $W$ is the virtual-photon proton centre of mass energy. Particular emphasis is placed on the dependence of the shape variables, measured in the $\gamma^*-$pomeron rest frame, on the mass of the hadronic final state, $M_X$. With increasing $M_X$ the multihadronic final state becomes more collimated and planar. The experimental results are compared with several models which attempt to describe diffractive events. The broadening effects exhibited by the data require in these models a significant gluon component of the pomeron.