Particle Physics · undergrad

Cross Section and Luminosity

The basic language for event rates in scattering experiments.

Published Apr 26, 2026 · 1 min

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Cross Section

A cross section $\sigma$ measures the effective probability for a scattering process. It has units of area.

The event rate is

R=\mathcal L\sigma,

where $\mathcal L$ is the luminosity.

Theory predicts cross sections; experiments measure event rates. Luminosity is the bridge between them.

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