Deep inelastic scattering with leading protons or large rapidity gaps at HERA

TL;DR

This paper studies diffractive deep inelastic scattering at HERA, analyzing events with large rapidity gaps and leading protons to understand the underlying exchange mechanisms and their dependence on kinematic variables.

Contribution

It provides detailed measurements of the cross section as functions of t, Phi, Q^2, x_P, and beta, including direct detection of leading protons, offering new insights into diffraction at high energies.

Findings

Cross sections depend on t and azimuthal angle Phi.

Data show the relationship between Q^2, x_P, and beta in diffractive processes.

Results support models of diffraction involving pomeron exchange.

Abstract

The dissociation of virtual photons, $\gamma^{\star} p \to X p$, in events with a large rapidity gap between $X$ and the outgoing proton, as well as in events in which the leading proton was directly measured, has been studied with the ZEUS detector at HERA. The data cover photon virtualities $Q^2>2$ GeV$^2$ and $\gamma^{\star} p$ centre-of-mass energies $40<W<240$ GeV, with $M_X>2$ GeV, where $M_X$ is the mass of the hadronic final state, $X$. Leading protons were detected in the ZEUS leading proton spectrometer. The cross section is presented as a function of $t$, the squared four-momentum transfer at the proton vertex and $\Phi$, the azimuthal angle between the positron scattering plane and the proton scattering plane. It is also shown as a function of $Q^2$ and $\xpom$, the fraction of the proton's momentum carried by the diffractive exchange, as well as $\beta$, the Bjorken variable defined with respect to the diffractive exchange.