Deeply inelastic pions in the exclusive reactionp(e,e′π+)nabove the resonance region

Abstract

A model for the $p(e,{e}^{\ensuremath{'}}{\ensuremath{\pi}}^{+})n$ reaction which combines an improved treatment of gauge invariant meson-exchange currents and hard deep-inelastic scattering (DIS) of virtual photons off nucleons is proposed. It is shown that DIS dominates and explains the transverse response at moderate and high photon virtualities ${Q}^{2}$, whereas the longitudinal response is dominated by hadronic degrees of freedom and the pion electromagnetic form factor. This leads to a combined description of the longitudinal and transverse components of the cross section in a wide range of photon virtuality ${Q}^{2}$ and momentum transfer to the target $t$ and solves the longstanding problem of the observed large transverse cross sections. The latter are shown to be sensitive to the intrinsic transverse momentum distribution of partons.