Predictions for the forward cone in diffractive deep inelastic scattering

We calculate the diffraction slope B-D for diffractive deep inelastic scatt ering. We find a counterintuitive rise of B-D in going from exclusive diffr active excitation of vector mesons to excitation of continuum states with M (2)similar to Q(2). For the small-mass continuum we predict a rapid variati on of B-D with M-2 on a scale of m(V)(2) and a sharp drop of B-D for a smal l-mass continuum above the vector meson excitation. (C) 1998 American Insti tute of Physics. [S0021-3640(98)00220-5].