Cherenkov detector
The direction this light is emitted is on a cone with angle θc about the direction in which the particle is moving, with cos(θc) = c/nv (c = the vacuum speed of light, n = the refractive index of the medium, and v is the speed of the particle).The angle of the cone θc thus is a direct measure of the particle's speed.Some sensor technologies explicitly aim at Cherenkov light produced (also) by secondary particles, be it incoherent emission as occurring in an electromagnetic particle shower or by coherent emission, for example Askaryan effect.Binary information can be based on the absence or presence of detected Cherenkov radiation.In the simple case of a threshold detector, the mass-dependent threshold energy allows the discrimination between a lighter particle (which does radiate) and a heavier particle (which does not radiate) of the same energy or momentum.