  The differential cross section dsigma/dt of elastic photoproduction of J/Psi
at different gamma p center of mass energies W are used to determine the
properties of the exchanged trajectory in the reaction gamma p --> J/Psi p. In
the region |t| < 1 GeV^2, the resulting trajectory is alpha(t) = (1.153 \pm
0.027) + (-0.001 \pm 0.072)t. The vanishing value of the slope of the
trajectory is an experimental evidence for no shrinkage and thus for the
perturbative nature of the exchange.
