2021 Impact factor 4.991
Particles and Fields
Eur. Phys. J. C 17, 113-119
DOI 10.1007/s100520000467

Semi-exclusive production of photons at HERA

P. Hoyer1 - M. Maul2 - A. Metz3

1 NORDITA, Blegdamsvej 17, 2100 Copenhagen, Denmark
2 Department of Theoretical Physics, Lund University, Sölvegatan 14 a, 223 62 Lund, Sweden
3 DAPNIA/SPhN, CEA-Saclay, 91191 Gif-sur-Yvette, France

Received: 27 March 2000 / Revised version: 6 June 2000 /
Published online: 9 August 2000 - © Springer-Verlag 2000

Abstract
We study the feasibility of measuring the semi-exclusive photon production $\gamma + p \to \gamma + Y$ at HERA. The cross section of photons produced at large transverse momenta, recoiling off an inclusive system Y of limited mass, can without photon isolation cuts simply be expressed in terms of hard PQCD subprocesses and standard target parton distributions. With the help of event generators we identify the kinematic region where quark and gluon fragmentation processes can be neglected. The cross section in this semi-exclusive region is large enough to be measured with an upgraded HERA luminosity of ${\cal L} = 100\,{\mathrm {pb}}^{-1}$.
The subprocesses of lowest order in $\alpha_{\mathrm {s}}$ are suppressed at low recoil masses MY, compared to higher order gluon exchange, i.e. BFKL contributions. The distinct MY-dependence makes it possible to determine experimentally the kinematic range where the higher order processes dominate.


Copyright Società Italiana di Fisica, Springer-Verlag 2000