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

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 $x_F$ 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 $131{\text{pb}}^{-1}$. The measurement is restricted to photons and neutrons in the pseudorapidity range $\mathit{\eta }>7.9$ and covers the range of negative four momentum transfer squared at the positron vertex $6<Q^2<100$ GeV${}^2$, of inelasticity $0.05<y<0.6$ and of $70<W<245$GeV. To test the Feynman scaling hypothesis the $W$ dependence of the $x_F$ 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.