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

The exclusive photoproduction reaction γp→ϒ(1S)pγp→ϒ(1S)p has been studied with the ZEUS detector in ep collisions at HERA using an integrated luminosity of 468 pb−1468 pb−1. The measurement covers the kinematic range 60<W<220 GeV60<W<220 GeV and Q2<1 GeV2Q2<1 GeV2, where W is the photon-proton centre-of-mass energy and Q2Q2 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=4.3−1.3+2.0(stat.)−0.6+0.5(syst.) GeV−2. This constitutes the first measurement of the t dependence of the γp→ϒ(1S)pγp→ϒ(1S)p cross section.