Comparison of Deep Inelastic Scattering with Photoproduction Interactions at HERA

TL;DR

This paper compares photon-proton and deep-inelastic scattering interactions at HERA, revealing their similarities and analyzing energy flow and event rates to understand the photon's hadronic nature.

Contribution

It provides a comparative analysis of $ ext{γ}p$ and $ ext{γ}^* p$ interactions, highlighting their similarities and the hadronic behavior of the photon at different virtualities.

Findings

Similarity between $ ext{γ}p$ and $ ext{γ}^* p$ interactions observed.

Transverse energy flow patterns are comparable in both interaction types.

Photon develops as a hadronic object in high-energy collisions.

Abstract

Photon-proton ($\gamma p$) interactions with~$Q^2<10^{-2}$~GeV$^2$ and deep-inelastic scattering ($\gamma^* p$) interactions with photon virtualities $Q^2>5$~GeV$^2$ are studied at the high energy electron-proton collider HERA. The transverse energy flow and relative rates of large rapidity gap events are compared in the two event samples. The observed similarity between $\gamma p$ and $\gamma^* p$ interactions can be understood in a picture where the photon develops as a hadronic object. The transverse energy density measured in the central region of the collision, at $\eta^*=0$ in the $\gamma^* p$ centre of mass frame, is compared with data from hadron-hadron interactions as function of the CMS energy of the collision.