Particle track

A particle track is a reconstructed trajectory inferred from spatially separated detector measurements associated with a particle. Individual hits are observations; fitting a track combines them with a propagation model, measurement errors and possible scattering.

In a uniform magnetic field, a charged particle follows a helical trajectory in the ideal limit. Its transverse momentum is $p_{\perp }=|q|BR$, where $R$ is the projected curvature radius in SI units. Curvature therefore constrains momentum, while its direction constrains the charge sign. Neutral particles generally require indirect reconstruction through secondary charged particles or other interaction signatures rather than an ordinary continuous charged-particle track.