Diffraction at HERA

TL;DR

This paper reviews the results from HERA experiments on diffraction phenomena in electron-proton collisions, highlighting insights into low Bjorken-x physics, parton density behavior, and non-linear QCD dynamics.

Contribution

It provides a comprehensive review of experimental findings on diffraction at HERA, emphasizing the role of diffractive processes in understanding low-x QCD physics.

Findings

Observation of geometric scaling in diffraction data

Evidence of non-linear dynamics taming parton density growth

High rate of diffractive processes at low Bjorken-x

Abstract

Between 1992 and 2007, the HERA accelerator provided $ep$ collisions at center of mass energies beyond $300 \ {\rm GeV}$ at the interaction points of the H1 and ZEUS experiments. Interesting results to emerge relate to the newly accessed field of perturbative strong interaction physics at low Bjorken-$x$, where parton densities become extremely large. Questions arise as to how and where non-linear dynamics tame the parton density growth and challenging features such as geometric scaling are observed. Central to this low $x$ physics landscape is a high rate of diffractive processes, in which a colorless exchange takes place and the proton remains intact. A review is given for main results obtained by H1 and ZEUS experiments in this field.