Measurement of Feynman-x Spectra of Photons and Neutrons in the Very Forward Direction in DIS at HERA

H1 $\it ep$ scattering data taken at HERA in the years 2006-7 are used to measure the production of very forward directed photons and neutrons. Normalised cross sections are given as a function of Feynman-x and of W , the centre-of-mass energy of the virtual photon-proton system. The phase space covered is defined by the ranges 6 < $Q^{2}$ < 100 $GeV^{2}$, 0.05 < y < 0.6, 70 < W < 245 GeV andη > 7.9, where $Q^{2}$ is the photon virtuality, y the inelasticity and η the pseudorapidity in the laboratory frame. The integrated luminosity is 131 $pb^{−1}$. Comparisons to the data are made with the predictions of several models used in cosmic ray physics for the simulation of hadronic interactions in the Earth atmosphere. The hypothesis of Feynman Scaling is tested, by studying the W-dependence of the cross sections differential in Feynman-x. This is the first direct experimental test of Feynman Scaling for photon and neutronproduction in the very forward direction at HER