Measurement of Feynman-xspectra of photons and neutrons in the very forward direction in deep-inelastic scattering at HERA

Armen Buniatyan,On Behalf Of The H1 Collaboration

doi:10.1051/epjconf/20159913002

Abstract

Measurements of normalised cross sections for the production of photons and neutrons at very small angles with respect to the proton beam direction in deep-inelastic ep scattering at HERA are presented as a function of the Feynman variable xF and of the centre-of-mass energy of the virtual photon-proton system W. The data are taken with the H1 detector in the years 2006 and 2007 and correspond to an integrated luminosity of 131 pb−1. The measurement is restricted to photons and neutrons in the pseudorapidity range η > 7.9 and covers the range of negative four momentum transfer squared at the positron vertex 6 < Q2 < 100 GeV2, of inelasticity 0.05 < y < 0.6 and of 70 < W < 245 GeV. To test the Feynman scaling hypothesis the W dependence of the xF dependent cross sections is investigated. Predictions of deep-inelastic scattering models and of models for hadronic interactions of high energy cosmic rays are compared to the measured cross sections.

Highlights

Measurements of particle production at very small polar angles with respect to the proton beam direction in positron-proton collisions are important inputs for the theoretical understanding of proton fragmentation mechanisms
These analyses have demonstrated that models of deep-inelastic scattering (DIS) are able to reproduce the forward baryon measurements if contributions from different production mechanisms are considered, such as string fragmentation, pion exchange, diffractive dissociation and elastic scattering of the proton [6, 7]
Within uncertainties the W dependence of the cross section is independent of the presence of a forward neutron or a forward photon, as predicted by the limiting fragmentation hypothesis [10, 11]

Summary

Introduction

Measurements of particle production at very small polar angles with respect to the proton beam direction in positron-proton collisions are important inputs for the theoretical understanding of proton fragmentation mechanisms. Measurements of these forward particles valuable for high energy cosmic ray experiments, as they provide important new constraints for high energy air shower models [1, 2]. The H1 and ZEUS experiments at the ep collider HERA have studied the production of forward baryons (protons and neutrons) and photons, which carry a large fraction of the longitudinal momentum of the incoming proton [3,4,5,6,7,8,9]. The measurements confirm the hypothesis of limiting fragmentation [10, 11], according to which, in the high-energy limit, the cross section for the inclusive production of particles in the target fragmentation region is independent of the incident projectile energy

Methods

Results

Conclusion