On the slope of the differential cross section for the photo- and electroproduction of vector mesons

The photo- and electroproduction of ϱ mesons at high energy is examined in a simple Regge-pole model with q2 dependent residues. The behaviour of the differential cross section at t=0 and of its slope, as a function of the q2 and of the photon energy, are correlated, and good fits to the data are obtained.