Hard diffractive electroproduction, transverse momentum distribution, and QCD vacuum structure

Wt study the impact of the ''intrinsic'' hadron transverse momentum on the pre-asymptotic behavior of the diffractive electroproduction of a longitudinally polarized rho meson. Surprisingly, we find the onset of the asymptotic regime in this problem to be rather low, Q(2) similar or equal to 10 GeV2 when power corrections due to the transverse momentum do not exceed 20% in the amplitude. This drastically contrasts with exclusive amplitudes where the asymptotics start much higher, Q(2) = 50-100 GeV2. The sources of such unexpected behavior are traced back to some general (the quark-hadron duality) as well as more silent (properties of higher dimensional vacuum condensates) features of QCD.