10.1007/s11450-008-3016-1

Abstract

It is shown that, under kinematical conditions of quasielastic knockout, the differential cross section for the exclusive process p(e, e π + )n induced by longitudinal virtual photons γ * L changes its physical nature as the recoil momentum |k| of the spectator nucleon grows from values in the range |k| ∼ 0.1-0.4 GeV/c, which are typical in studying the pion cloud of the nucleon, to values around |k| ∼ 1 GeV/c. Calculations within the 3 P 0 quark microscopic model reveal that the amplitudes for the deexcitation of vector and pseudovector mesons via the processes ρ + + γ * L → π + and b + 1 + γ * L → π + become dominant here. Concurrently, the effective momentum distributions develop a substantial angular anisotropy of about 50% with respect to the angle between the momentum of the photon γ * L and the recoil momentum of the spectator nucleon, the longitudinal differential cross sections undergoing respective changes. In this region, the energy of knock-on pions is expected to be about 5 GeV under conditions of quasilastic kinematics.