Speaker
Dorota Szuba
(DESY)
Description
The exclusive photoproduction reaction gamma p -> Upsilon p has been
studied with the ZEUS experiment in ep collisions at HERA using an
integrated luminosity of 468 pb^-1. The measurement covers the kinematic
range 60<W<220 GeV and Q^2<1 GeV^2, where W is the photon-proton
centre-of-mass energy and Q^2 is the photon virtuality. These results,
which represent the analysis of the full ZEUS data sample for this channel,
are compared to predictions based on perturbative QCD.
The proton-dissociative diffractive photoproduction of J/psi mesons has
been studied in ep collisions with the ZEUS detector at HERA using an
integrated luminosity of 112 pb^{-1}. The cross section is presented
as a function of the photon-proton centre-of-mass energy and of the squared
four-momentum transfer at the proton vertex. The results are compared to
perturbative QCD calculations.
The first measurement of diffractive scattering of quasi-real photons with
large momentum transfer gamma p -> gamma Y, where Y is the proton dissociative
system, is made using the H1 detector at HERA. The measurement is performed
for initial photon virtualities Q^2 < 0.01 GeV^2. Cross sections are measured
as a function of W, the incident photon-proton entre of mass energy, and t,
the square of the four-momentum transferred at the proton vertex, in the range
175 < W < 247 GeV and 4<|t|<36 GeV^2. The W dependence is well described by a
model based on perturbative QCD using a leading logarithmic approximation of
the BFKL evolution. The measured |t| dependence is harder than that predicted
by the model and those observed in exclusive vector meson production.
Based on data collected with the H1 detector at HERA in 2005, cross sections
for elastic rho photoproduction have been measured at momentum transfer
|t|<0.58 GeV^2 and photon-proton centre-of-mass energies 20<90GeV. This data
has been combined with cross sections published previously by the Omega and
ZEUS collaborations in a global fit to determine the pomeron trajectory
alpha(t) in 13 bins of t from the W-dependence of the elastic rho production
cross section.
Primary authors
Dorota Szuba
(DESY)
Monica Turcato ZEUS Collaboration
(Hamburg University)
