The Scale Dependence of Inclusive ep Scattering in the Resonance Region

We examine the scale dependence in the resonance region of inclusive ep scattering. In particular we discuss the invariants other than Q, which have been proposed as a scale for pQCD evolution in a kinematical regime where both infrared singularities and power corrections are expected to be largest. We show that the region where most of the present data are available, can be described using NLO pQCD evolution at fixed invariant mass, W , plus a leading order power correction term. We find that the coefficient of the power correction at W 2 < 4GeV 2 is relatively small, i.e. comparable in size to the one obtained in the large W 2 region. It has been long known that a fully quantitative description of proton structure in terms of parton distribution functions must account for power corrections to the Q dependence of the data, in addition to the predicted perturbative-QCD (pQCD) behavior. Power corrections are indeed observed in experiments as discrepancies between fixed order perturbative predictions and the data. Their theoretical interpretation is however a less well defined issue. In Deep Inelastic Scattering (DIS), in particular, the short-distance scattering involving single, non-interacting partons is expected to give way to