Measurement of dijet photoproduction for events with a leading neutron at HERA

TL;DR

This paper measures dijet photoproduction with a leading neutron at HERA, analyzing cross sections and neutron yields to test pion-exchange models and understand the underlying physics of forward neutron production.

Contribution

It provides detailed measurements of dijet photoproduction with leading neutrons and compares results to pion-exchange models, offering insights into neutron production mechanisms.

Findings

Neutron yield depends only on proton energy fraction in the forward region.

Results are consistent with a simple pion-exchange model.

No definitive evidence of rescattering effects was observed.

Abstract

Differential cross sections for dijet photoproduction and this process in association with a leading neutron, e+ + p -> e+ + jet + jet + X (+ n), have been measured with the ZEUS detector at HERA using an integrated luminosity of 40 pb-1. The fraction of dijet events with a leading neutron was studied as a function of different jet and event variables. Single- and double-differential cross sections are presented as a function of the longitudinal fraction of the proton momentum carried by the leading neutron, xL, and of its transverse momentum squared, pT^2. The dijet data are compared to inclusive DIS and photoproduction results; they are all consistent with a simple pion-exchange model. The neutron yield as a function of xL was found to depend only on the fraction of the proton beam energy going into the forward region, independent of the hard process. No firm conclusion can be drawn on the presence of rescattering effects.