Momentum transfer dependence of heavy quarkonium electroproduction

We investigate the momentum transfer dependence of differential cross sections $dsigma/dt$ in diffractive electroproduction of heavy quarkonia on proton targets. Model predictions for $dsigma/dt$ within the light-front QCD dipole formalism are based on a realistic model for a proper correlation between the impact parameter $vec b$ of a collision and color dipole orientation $vec r$. We demonstrate a significance of $vec b-vec r$ correlation by comparing with a standard simplification $vec{b}parallelvec{r}$, frequently used in the literature.