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Exclusive processes in hard electroproduction is one of the best place forunderstanding the factorization properties of QCD. The HERA experiment recentlyprovided precise data for rho electroproduction, including all spin densitymatrix elements. From QCD, it is expected that such a process should factorizebetween a hard (calculable) coefficient function, and hadronic (p and rho)matrix elements. Such a factorization is up to now only proven for alongitudinaly polarized rho. Within the kt-factorization approach (valid atlarge s_{gamma* p}), we evaluate the impact factor of the transition gamma* ->rhoT taking into account the twist 3 contributions. We show that a gaugeinvariant expression is obtained with the help of QCD equations of motion. Moregenerally, relying on these equations and on the invariance under rotation onthe light-cone of the factorized amplitude, the non-perturbative DistributionAmplitudes can be reduced to a minimal set. This opens the way to a consistenttreatment of factorization for exclusive processes with a transversallypolarized vector meson. We prove the equivalence of two proposedparametrizations of the rhoT distribution amplitudes.

QCD factorization beyond leading twist in exclusive processes: rhoT-meson production