Exclusive leptoproduction of
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
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