Model independent study of massive lepton elastic scattering on the proton, beyond the Born approximation

TL;DR

This paper derives model-independent formulas for polarization observables in muon-proton elastic scattering, incorporating lepton mass and two-photon exchange effects, providing insights beyond the Born approximation.

Contribution

It introduces a comprehensive, model-independent framework for analyzing polarization observables in muon-proton scattering, including two-photon exchange contributions and lepton mass effects.

Findings

Polarization observables are significantly affected by two-photon exchange.

The formalism accounts for lepton mass, extending previous massless approximations.

General influence of two-photon exchange on scattering observables is established.

Abstract

Model independent expressions for all polarization observables in $\mu+p\to \mu+p$ elastic scattering are obtained, taking into account the lepton mass and including the two-photon exchange contribution. The spin structure of the matrix element is parametrized in terms of six independent complex amplitudes, functions of two independent kinematical variables. General statements about the influence of the two--photon--exchange terms on the differential cross section and on polarization observables are given. Polarization effects have been investigated for the case of a longitudinally polarized lepton beam and polarized nucleon in the final state.