文摘
The exclusive photoproduction reaction has been studied with the ZEUS detector in ep collisions at HERA using an integrated luminosity of . The measurement covers the kinematic range and , where W is the photon-proton centre-of-mass energy and is the photon virtuality. 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, yielding . This constitutes the first measurement of the t dependence of the cross section.