2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/199527We evaluate the two-loop QED corrections to the Bhabha scattering cross section which involve the vacuum polarization by heavy fermions of arbitrary mass m_f >> m_e. The results are valid for generic values of the Mandelstam invariants s,t,u >> m_e^2.13 pages, 6 figures. Equations in the appendix generalized to the heavy-quark caseHigh Energy Physics - Phenomenologytext