A particle passing through a material at a velocity greater than that at which light can travel through the material emits light. This is similar to the production of a sonic boom when an airplane is traveling through the air faster than sound waves can move through the air. 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.
If the momentum of the particle is known, as in tracking detectors, one can get at the mass of the particle.
Gases aerogels and quarz have been used for detecting the radiation.
High energy physics has been using cherenkov radiation detectors since the LEP experiment Delphi, the material just needs to be transparent with index of refraction larger than 1, for particle identification. The momentum of the particles is found in tracking detectors and the angle of radiation gives the mass:
The ring-imaging Cherenkov, or RICH, detector is a device for identifying the type of an electrically charged subatomic particle of known momentum, that traverses a transparent refractive medium, by measurement of the presence and characteristics of the Cherenkov radiation emitted during that traversal. RICH detectors were first developed in the 1980s and are used in high energy elementary particle- , nuclear- and astro-physics experiments.
The different particle types follow distinct contours of constant mass, smeared by the effective angular resolution of the RICH detector; at higher momenta each particle emits a number of Cherenkov photons which, taken together, give a more precise measure of the average $θ_c$ than does a single photon, allowing effective particle separation to extend beyond 100 GeV in this example.