https://doi.org/10.1140/epjc/s10052-011-1771-6
Regular Article - Experimental Physics
Measurement of photon production in the very forward direction in deep-inelastic scattering at HERA
1
I. Physikalisches Institut der RWTH, Aachen, Germany
2
Vinca Institute of Nuclear Sciences, University of Belgrade, 1100, Belgrade, Serbia
3
School of Physics and Astronomy, University of Birmingham, Birmingham, UK
4
Inter-University Institute for High Energies ULB-VUB, Brussels and Universiteit Antwerpen, Antwerpen, Belgium
5
National Institute for Physics and Nuclear Engineering (NIPNE), Bucharest, Romania
6
Rutherford Appleton Laboratory, Chilton, Didcot, UK
7
Institute for Nuclear Physics, Cracow, Poland
8
Institut für Physik, TU Dortmund, Dortmund, Germany
9
Joint Institute for Nuclear Research, Dubna, Russia
10
CEA, DSM/Irfu, CE-Saclay, Gif-sur-Yvette, France
11
DESY, Hamburg, Germany
12
Institut für Experimentalphysik, Universität Hamburg, Hamburg, Germany
13
Max-Planck-Institut für Kernphysik, Heidelberg, Germany
14
Physikalisches Institut, Universität Heidelberg, Heidelberg, Germany
15
Kirchhoff-Institut für Physik, Universität Heidelberg, Heidelberg, Germany
16
Institute of Experimental Physics, Slovak Academy of Sciences, Košice, Slovak Republic
17
Department of Physics, University of Lancaster, Lancaster, UK
18
Department of Physics, University of Liverpool, Liverpool, UK
19
Queen Mary and Westfield College, London, UK
20
Physics Department, University of Lund, Lund, Sweden
21
CPPM, Aix-Marseille Univ., CNRS/IN2P3, 13288, Marseille, France
22
Departamento de Fisica Aplicada, CINVESTAV, Mérida, Yucatán, Mexico
23
Departamento de Fisica, CINVESTAV IPN, México City, Mexico
24
Institute for Theoretical and Experimental Physics, Moscow, Russia
25
Lebedev Physical Institute, Moscow, Russia
26
Max-Planck-Institut für Physik, München, Germany
27
LAL, Université Paris-Sud, CNRS/IN2P3, Orsay, France
28
LLR, Ecole Polytechnique, CNRS/IN2P3, Palaiseau, France
29
LPNHE, Université Pierre et Marie Curie Paris 6, Paris, France
30
Université Denis Diderot Paris 7, CNRS/IN2P3, Paris, France
31
Faculty of Science, University of Montenegro, Podgorica, Montenegro
32
Institute of Physics, Academy of Sciences of the Czech Republic, Praha, Czech Republic
33
Faculty of Mathematics and Physics, Charles University, Praha, Czech Republic
34
Dipartimento di Fisica Università di Roma Tre and INFN Roma 3, Roma, Italy
35
Institute for Nuclear Research and Nuclear Energy, Sofia, Bulgaria
36
Institute of Physics and Technology of the Mongolian Academy of Sciences, Ulaanbaatar, Mongolia
37
Paul Scherrer Institut, Villigen, Switzerland
38
Fachbereich C, Universität Wuppertal, Wuppertal, Germany
39
Yerevan Physics Institute, Yerevan, Armenia
40
DESY, Zeuthen, Germany
41
Institut für Teilchenphysik, ETH, Zürich, Switzerland
42
Physik-Institut der Universität Zürich, Zürich, Switzerland
* e-mail: daum@mail.desy.de
Received:
29
June
2011
Revised:
1
September
2011
Published online:
13
October
2011
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 pb−1. The analysis covers the range of negative four momentum transfer squared at the positron vertex 6<Q 2<100 GeV2 and inelasticity 0.05<y<0.6. Cross sections are measured for the most energetic photon with pseudorapidity η>7.9
as a function of its transverse momentum and longitudinal momentum fraction of the incoming proton
. In addition, the cross sections are studied as a function of the sum of the longitudinal momentum fraction
of all photons in the pseudorapidity range η>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.
© Springer-Verlag / Società Italiana di Fisica, 2011