  We derive a full set, and determine the twist, of helicity amplitudes for
diffractive production of light to heavy vector mesons in deep inelastic
scattering. For large $Q^{2}$ all helicity amplitudes but the double-flip are
calculable in perturbative QCD and are proportional to the gluon structure
function of the proton at a similar hard scale. We find a substantial breaking
of the $s$-channel helicity conservation which must persist also in real
photoproduction.
