Target Fragmentation in $pp$, $ep$ and $\gamma p$ Collisions at High Energies

TL;DR

This paper models target fragmentation in high-energy proton-proton and gamma-proton collisions using the meson cloud picture, analyzing neutron production and rescattering effects across different reaction types and energies.

Contribution

It introduces a unified approach to describe target fragmentation in various high-energy collisions, incorporating rescattering effects and form factor adjustments based on experimental data.

Findings

Rescattering effects are weaker in photoproduction than in hadronic reactions.

Deep inelastic scattering shows reduced but persistent screening effects at high Q^2.

Neutron energy distributions shift due to absorptive rescattering, indicating interaction dynamics.

Abstract

We calculate target fragmentation in $p p \to n X$ and $\gamma p \to n X $ reactions in the meson cloud picture of the nucleon. The $p p \to n X$ reaction is used to fix the $pn\pi^+$ form factor for three different models. We take into account the possible destruction of the residual neutron by the projectile. Using the form factor from the hadronic reaction we calculate photoproduction and small $x_{Bj}$ electroproduction of forward neutrons at HERA. Here the $q \bar q$ dipoles in the photon can rescatter on the residual neutron. In photoproduction we observe slightly less absorption than in the hadronic reaction. For deep inelastic events ($Q^2>10$ GeV$^2$) screening is weaker but still present at large $Q^2$. The signature for this absorptive rescattering is a shift of the $d\sigma/dE_n$ distribution to higher neutron energies for photofragmentation.