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Particle Identification with RICH Detectors.
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Particle Identification with RICH Detectors In a vacuum, nothing can travel faster than light. But light slows down if it passes through a material, making it possible for a particle travelling through the same material to go faster than light. When it does this, a charged particle radiates a cone of light, called `Cerenkov light’. Particle physics detectors often profit from this phenomenon, by including a RICH sub-detector in their design, which focusses the cone of Cerenkov light into a ring of light using a mirror, and detects the ring using light sensitive detectors. The radius of the ring tells us the velocity of the particle, which, if we have also measured the particle’s momentum using another sub-detector, allow us to identify it. The mirror here dates from ~1985 and comes from the first RICH detector ever used in a particle physics experiment (the OMEGA spectrometer). The LHCb detector at the LHC collider also uses a RICH, to help it study the properties of hadrons containing b-quarks.