Lepton mass effects in the Bethe-Heitler process

TL;DR

This paper develops a comprehensive formalism to account for lepton mass effects in the Bethe-Heitler process, highlighting their significance in muon and electron scattering at specific kinematic regions.

Contribution

It introduces a full finite lepton mass formalism for the Bethe-Heitler process, emphasizing the impact of lepton mass and initial energy on cross sections.

Findings

Lepton mass effects dominate muon-induced proton cross sections.

Mass effects are significant for electron scattering at small $x_B$.

Sensitivity to nucleon isospin is analyzed.

Abstract

We develop the full finite lepton mass formalism for the production of real photons via the Bethe-Heitler reaction of unpolarized leptons off unpolarized nucleons. Genuine lepton mass effects are described, in particular their dependence upon the lepton mass and the initial beam energy, as well as their sensitivity to the nucleon isospin. In the minimum momentum transfer region, these effects dominate the muon induced proton cross section and become significant for electron scattering at small $x_B$.