Large nonperturbative effects for smallxEin lepton-proton scattering

A rigorous nonperturbative approach to radiative corrections in charged-lepton scattering is derived from a rearrangement of the QED perturbation series. The new series is covariant and involves no cutoff. Successive terms, corresponding to an increasing number of "oblique" photons, incorporate the emission of an arbitrary number of collinear photons. The infrared spectrum of an oblique photon is shown to be suppressed. The zero- and one-oblique-photon terms are computed and numerical results for the elastic contribution are presented. In the very inelastic regime, small $x_E$ and large $Q_E^2$, we find an elastic contribution to the cross section much larger than that predicted by standard perturbation theory. We note that our results may modify somewhat the current picture of scaling violations, at least in the very inelastic regime.