Measurement of the t dependence in exclusive photoproduction of ϒ(1S) mesons at HERA

Abstract

The exclusive photoproduction reaction γ p →Υ (1S)p has been studied with the ZEUS detector 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 GeV2, where W is the photon–proton centre-of-mass energy and Q 2 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 b = 4.3+2.0−1.3(stat.)+0.5−0.6(syst.) GeV−2. This constitutes the first measurement of the t dependence of the γ p→Υ (1S)p cross section.