Diffractive Photoproduction of Psi(2S) Mesons at HERA

Results on diffractive photoproduction of {psi(2S)} mesons are presented using data collected between 1996 and 2000 with the H1 detector at the {HERA} ep collider. The data correspond to an integrated luminosity of 77 pb{\textasciicircum}(-1). The energy dependence of the diffractive {psi(2S)} cross section is found to be similar to or possibly somewhat steeper than that for J/psi mesons. The dependences of the elastic and proton dissociative {psi(2S)} photoproduction cross sections on the squared momentum transfer t at the proton vertex are measured. The t-dependence of the elastic channel, parametrised as e{\textasciicircum}(bt), yields b\_(el){\textasciicircum}{(psi(2S))=(4.31+-0.57+-0.46)} {GeV{\textasciicircum}(-2)}, compatible with that of the J/psi. For the proton dissociative channel the result b\_(pd){\textasciicircum}{(psi(2S))=(0.59+-0.13+-0.12)} {GeV{\textasciicircum}(-2)} is 2.3 standard deviations smaller than that measured for the J/psi. With proper account of the individual wavefunctions theoretical predictions based on perturbative {QCD} are found to describe the measurements well.