Diffractive Vector Meson Production in a Unified Κ-factorization Approach

This expression contains two pieces non-calculable within pQCD: the vector meson WF ψ(z,~k) and the differential gluon structure function (DGSF) F(x,~κ, ~ ∆). The principal novelty of this work is that DGSF is now under control. The off-forward DGSF F(x,~κ, ~ ∆) can be linked to the forward DGSF, which has been recently determined from experimental data on F2p in the whole Q domain . This dramatically reduces the level of ambiguity in diffractive vector meson production calculations, leaving us only with one unknown quantity — the vector meson WF. The vector meson WF involves two components: the spinorial structure of the qq̄V vertex and the radial WF ψ(k). In our work we consistently used the spinorial structures corresponding to qq̄ pair sitting in pure S or D wave state . This allows us to address production of both ground (1S) and excited (2S, D wave) vector meson states as well as S/D wave mixed states. For the radial WF we chose a simple soft WF Ansatz (i.e. without specific large-k, or short distance, enhancement) with parameters adjusted to match the vector meson V → ee decay width.