Space-time structure of hard-scattering processes

Recent studies of exclusive electroproduction of vector mesons at JLab make it possible for the first time to play with two independent hard scales: the virtuality Q(2) of the photon, which sets the observation scale, and the momentum transfer t to the hadronic system, which sets the interaction scale. They reinforce the description of hard-scattering processes in terms of few effective degrees of freedom relevant to the JLab-Hermes energy range.