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 m(e), m (f) and the Mandelstam invariants s, t. u. We determine the limit of fixed scattering angle and high energy, assuming the hierarchy of scales m(e)(2) << m(f)(2) << 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. (C) 2007 Elsevier B.V. All rights reserved.