 The Bhabha scattering rate is used as a luminosity monitor in electron-positron colliders.To leading order, the spin-averaged differential cross section for this process is

where "s","t", and "u" are the Mandelstam variables, formula_3 is the fine-structure constant, and formula_4 is the scattering angle.This cross section is calculated neglecting the electron mass relative to the collision energy and including only the contribution from photon exchange.