  The cross section for coherent nuclear processes in which an incident meson
or photon dissociates diffractively into two jets of high relative transverse
momentum (between about 1 and 3 GeV/c) is found to be proportional in QCD to
$A^2$ in a wide kinematical region. The leading correction to this is a
significant positive term $\propto A^{7/3}$ caused by nuclear
multiple-scattering. We find also that shadowing of hard diffractive processes
reappears as a leading twist effect in the TeV energy range.
