Bhabha Scattering

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, ${\displaystyle \alpha }$ is the fine-structure constant, and ${\displaystyle \theta }$ 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.

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