DOI 10.1007/s100520000483
Exclusive leptoproduction of 
mesons
from hydrogen at intermediate virtual photon energies
The HERMES Collaboration
A. Airapetian30 - et al.
30 Yerevan Physics Institute, 375036, Yerevan, Armenia
Received: 25 April 2000 / Revised version: 3 July 2000 /
Published online: 25 September 2000 - © Springer-Verlag 2000
Abstract
Measurements of the cross section for exclusive virtual-photoproduction
of
mesons
from hydrogen are reported. The data were collected by the HERMES experiment
using 27.5 GeV positrons incident on a hydrogen
gas target in the HERA storage ring. The invariant mass
W of the photon-nucleon system
ranges from 4.0 to 6.0 GeV, while the negative squared four-momentum Q2 of the virtual photon varies from 0.7 to 5.0 GeV2. The
present data together with most of the previous data in the
intermediate W-domain
are well described by a model that infers the W-dependence of the
cross section from the dependence on the Bjorken scaling variable x of the unpolarized structure function for deep-inelastic scattering.
In addition, a model calculation
based on Off-Forward Parton Distributions gives a fairly good account of the
longitudinal component of the
production cross section for
Q2 > 2 GeV2.
Copyright Società Italiana di Fisica, Springer-Verlag 2000
