Measurement of Photon Production in the Very Forward Direction in Deep-Inelastic Scattering at HERA

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.

Note:

19 pages, 6 figures and 2 tables

photon: electroproduction
positron p: deep inelastic scattering
differential cross section: measured
interaction: model
rapidity
longitudinal momentum
transverse momentum dependence
DESY HERA Stor
H1
production: small-angle

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Figures(18)

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