DOI: 10.1140/epjc/s2002-01130-2
Measurements of inelastic
and
photoproduction at HERA
The ZEUS Collaboration (Received: 22 October 2002 / Published online: 14 February 2003 )
Abstract
The cross sections for inelastic photoproduction of
and
mesons
have been measured in
ep collisions with the ZEUS detector at HERA, using an
integrated luminosity of 38.0 pb
-1. The events were required to have
0.1
< z < 0.9 and 50
< W < 180 GeV, where
z is the fraction of the
incident photon energy carried by the
in the proton rest frame and
W is the
photon-proton centre-of-mass energy. The
to
cross-sec tion ratio
was measured in the range
0.55 < z < 0.9. The
data, for various ranges
of transverse momentum, are compared to theoretical models incorporating colour-singlet
and colour-octet matrix elements. Predictions of a next-to-leading-order colour-singlet
model give a good description of the data, although there is a large normalisation
uncertainty. The
helicity distribution for
z > 0.4 is compared to
leading-order QCD predictions.
© Società Italiana di Fisica, Springer-Verlag 2003
