Two-loop fermionic corrections to massive Bhabha scattering

We evaluate the two-loop corrections to Bhabha scattering from fermion loops in the context of pure quantum electrodynamics. The differential cross section is expressed by a small number of master integrals with exact dependence on the fermion masses me,mfme,mf and the Mandelstam invariants s,t,us,t,u. We determine the limit of fixed scattering angle and high energy, assuming the hierarchy of scales me2≪mf2≪s,t,u. The numerical result is combined with the available non-fermionic contributions. As a by-product, we provide an independent check of the known electron-loop contributions.