Ring Imaging Cherenkov (RICH) detectors
Like VELO, the experiment's two RICH detectors are built for particle identification. Lying on either side of LHCb’s powerful magnet, the detectors are positioned to intercept particles flying at different speeds and angles.
RICH detectors work by measuring emissions of Cherenkov radiation. This phenomenon, often compared to the sonic boom produced by an aircraft breaking the sound barrier,
occurs when a charged particle passes through a certain medium (in this case, a dense gas) faster than light does. As it travels, the particle emits a cone of light, which the RICH detectors reflect onto an array of sensors using mirrors.
The shape of the cone of light depends on the particle’s velocity, enabling the detector to determine its speed. Scientists can then combine this information with a record of its trajectory (collected using the tracking system and a magnetic field) to calculate its mass, charge, and therefore its identity.
The two RICH detectors are responisible for identifying a range of different particles that result from the decay of B mesons, including pions, kaons and protons.