Polarization phenomena in e∓N elastic scattering, for axial parametrization of two-photon exchange

We analyze polarization phenomena for elastic lepton-nucleon scattering, parametrizing the 2gamma-exchange contribution, as the product of lepton and nucleon axial vector currents, that correspond to C = +1 exchange in the annihilation channel. We found two combinations of polarization observables (one for three Todd observables and another one for five T-even observables, which allow to measure the ratio G(E)(Q(2))/G(M)(Q(2)) of nucleon electromagnetic form factors in model-independent way, without any specific assumption about the 2gamma-exchange mechanism. Both these important combinations have a general character and do not depend on the choice of the spin structure for the 2gamma-exchange. (C) 2004 Elsevier B.V. All rights reserved.