Bhabha scattering

In quantum electrodynamics, Bhabha scattering is the electron-positron scattering process: In quantum electrodynamics, Bhabha scattering is the electron-positron scattering process: There are two leading-order Feynman diagrams contributing to this interaction: an annihilation process and a scattering process. Bhabha scattering is named after the Indian physicist Homi J. Bhabha. 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, α {displaystyle alpha } is the fine-structure constant, and θ {displaystyle heta } 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. This is a valid approximation at collision energies small compared to the mass scale of the Z boson, about 91 GeV; at higher energies the contribution from Z boson exchange also becomes important. In this article, the Mandelstam variables are defined by