Measurement of proton-dissociative diffractive photoproduction of vector mesons at large momentum transfer at HERA

Diffractive photoproduction of vector mesons, #gamma#p #-># VY, where Y is a proton-dissociative system, has been measured in e"+p interactions with the ZEUS detector at HERA using an integrated luminosity of 25 pb"-"1. The differential cross section, d#sigma#/dt, is presented for -t < 12 GeV"2, where t is the square of the four-momentum transferred to the vector meson. The data span the range in photon-proton centre-of-mass energy, W, from 80 GeV to 120 GeV. The t distributions are well fit by a power law, d#sigma#/dt #propor to# (-t)"-"n. The slope of the Pomeron trajectory, measured from the W dependence of the #rho#"0 and #phi# cross sections in bins of t, is consistent with zero. The ratios d#sigma#_#gamma#_p_#->#_#phi#_Y/dt to d#sigma#_#gamma#_p_#->#_#rho#_"0_Y/dt and d#sigma#_#gamma#_p_#->#_J_/_#psi#_Y/dt to d#sigma#_#gamma#_p_#->#_#rho#_"0_Y/dt increase with increasing -t. Decay-angle analyses for #rho#"0, #phi# and J/#psi# mesons have been carried out. For the #rho#"0 and #phi# mesons, contributions from single and double helicity flip are observed. The results are compared to expectations of theoretical models. (orig.)Available from TIB Hannover: RA 2999(02-072) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman