Speaker
Summary
The exclusive photoproduction reaction gamma p -> Upsilon(1S) p has been
studied with the ZEUS detector in ep collisions at HERA.
The exponential slope, b, of the t dependence of the cross section,
where t is the squared four-momentum transfer at the proton vertex,
has been measured.This constitutes the first measurement of the t dependence
of the gamma p -> Upsilon(1S) p cross section.
The differential cross sections as a function of t at lower energies were
studied in exclusive diffractive photoproduction of J/psi mesons with the H1
detector.
The exclusive electroproduction of two pions was measured by the ZEUS
experiment. The two-pion invariant-mass distribution is interpreted in terms
of the pion electromagnetic form factor, assuming that the
studied mass range includes the contributions of the rho,
rho' and rho'' vector-meson states.
