Electroproduction of vector mesons: factorization of end-point contributions

The end-point contributions in the quark longitudinal momentum fraction of the virtual photon ( g^*\gamma^* ) to vector meson (V) impact factor to the diffractive electroproduction amplitude can be factorized in terms of a generalized parton evolution of the target parton distribution. This result is used to model the helicity amplitudes g^* p ? V p\gamma^* p \rightarrow V p in terms of small x generalized parton distributions.