DOI 10.1007/s100520000374
Measurement of diffractive photoproduction of vector mesons
at
large momentum transfer at HERA
The ZEUS Collaboration
J. Breitweg - et al.
Argonne National Laboratory, Argonne, IL, USA
Received: 16 October 1999
/ Revised version: 17 January 2000
/
Published online: 6 April 2000
- © Springer-Verlag 2000
Abstract
Elastic and proton-dissociative photoproduction of ,
and
vector mesons (
,
,
respectively) have been measured in e+pinteractions at HERA up to -t=3 GeV2, where t is the
four-momentum transfer squared at the photon-vector-meson vertex.
The analysis is based on a data sample in which photoproduction
reactions were tagged by detection of the scattered positron in a
special-purpose calorimeter. This limits the photon virtuality, Q2,
to values less than 0.01 GeV2, and selects a
average
center-of-mass energy of
= 94 GeV. Results for the
differential cross sections,
,
for ,
and
mesons are presented and compared to the results of recent QCD
calculations. Results are also presented for the t-dependence of
the pion-pair invariant-mass distribution in the
mass
region and of the spin-density matrix elements determined from the
decay-angle distributions. The Pomeron trajectory has been derived
from measurements of the W dependence of the elastic differential
cross sections
for both
and
mesons.
Copyright Società Italiana di Fisica, Springer-Verlag 2000