  We study in a framework of QCD collinear factorization the processes of a
pion and a photon diffraction dissociation into two jets. The structure of
non-factorizable contributions is discussed. We argue that coherent production
of hard dijets by linearly polarized real photons can provide direct evidence
for chirality violation in hard processes, the first measurement of the
magnetic susceptibility of the quark condensate and the photon distribution
amplitude.
