The tauon is the heaviest lepton. Because of its large mass, it is the only lepton that can decay not only in the lighter leptons, so into an electron or a muon and neutrinos (leptonic decay) but also into a down and an anti-up quarks (hadronic decay). The tauon was discovered in the 1970s by M. Perl through the observation of its decay to muons and to electrons.
Tauons are naturally created in stellar explosions, or when fast protons from space impact the Earth's atmosphere. They can also be produced in high-energy physics experiments.
Due to their short lifetime, however, tauons decay much faster than muons, which is why they often cannot be observed directly, but only through their decay products. Such products can be detected in calorimeters. These detectors are specifically built to slow down and stop the particles and collect the entire energy released during these processes. When particles enter a calorimeter, a so-called particle shower begins: they decay into other particles that decay in turn. The shower proceeds until the produced particles are stable and have too little energy to further interact.
The sign shows an event display of the production of two taus in a high-energy physics detector. The one tau decays into a muon and neutrinos, while the other decays hadronically into three pions and a tau neutrino.
