Particle isolation

A collider isolation requirement limits additional tracks or deposited energy near a particle candidate. It suppresses candidates embedded in jets while preserving suitably separated prompt leptons or photons. The cone geometry, energy threshold and collision-pileup correction form part of the observable's experimental definition.

Lepton isolation restricts additional track momentum or calorimeter energy near a reconstructed lepton. It helps distinguish prompt leptons from jets and heavy-hadron decays. Detector acceptance, nearby signal particles and collision pileup affect its efficiency; a isolated photon uses a related isolation requirement rather than being a lepton.