  The production of photons at very small angles with respect to the proton
beam direction is studied in deep-inelastic positron-proton scattering at HERA.
The data are taken with the H1 detector in the years 2006 and 2007 and
correspond to an integrated luminosity of $126 \mathrm{pb}^{-1}$. The analysis
covers the range of negative four momentum transfer squared at the positron
vertex $6<Q^2<100$ GeV$^2$ and inelasticity $0.05<y<0.6$. Cross sections are
measured for the most energetic photon with pseudorapidity $\eta>7.9$ as a
function of its transverse momentum $p_T^{lead}$ and longitudinal momentum
fraction of the incoming proton $x_L^{lead}$. In addition, the cross sections
are studied as a function of the sum of the longitudinal momentum fraction
$x_L^{sum}$ of all photons in the pseudorapidity range $\eta>7.9$. The cross
sections are normalised to the inclusive deep-inelastic scattering cross
section and compared to the predictions of models of deep-inelastic scattering
and models of the hadronic interactions of high energy cosmic rays.

High Energy Physics - Experiment