https://doi.org/10.1140/epjc/s2004-02047-4
experimental physics
Dissociation of virtual photons in events with a leading proton at HERA
The ZEUS detector has been used to study dissociation of virtual photons in events with a leading proton, 
, in e
+
p collisions at HERA. The data cover photon virtualities in two ranges, 0.03 < Q
2 < 0.60 GeV2 and 2 < Q
2 < 100 GeV2, with M
X
> 1.5 GeV, where M
X
is the mass of the hadronic final state, X. Events were required to have a leading proton, detected in the ZEUS leading proton spectrometer, carrying at least 90% of the incoming proton energy. The cross section is presented as a function of t, the squared four-momentum transfer at the proton vertex, 
, the azimuthal angle between the positron scattering plane and the proton scattering plane, and Q
2. The data are presented in terms of the diffractive structure function, 
. A next-to-leading-order QCD fit to the higher-Q
2 data set and to previously published diffractive charm production data is presented.
© Springer-Verlag, 2004
