Mu3e

Mu3e is constructed at the Paul Scherrer Institute. It is planned to create the world's most intense muon beam which will allow to analyze two billion decays per second. This rate is necessary to study more than 10¹⁶ muon decays in total. Important backgrounds are the decays ${\displaystyle \mu ^{+}\to e^{+}e^{-}e^{+}{\bar {\nu _{\mu }}}\nu _{e}}$ and ${\displaystyle \mu ^{+}\to e^{+}{\bar {\nu _{\mu }}}\nu _{e}}$. To distinguish between signal and background, the detector has a spatial resolution better than 200 μm, a time resolution better than 100 ps and an energy resolution better than 0.5 MeV for the individual electrons. To minimize multiple scattering, the detector is built as light as possible. Semiconductor detectors^[4] are used for the spatial and energy resolution, scintillator fibers provide a good timing resolution. The whole experiment is in a magnetic field of 1 Tesla to determine the energy of the particles based on their curvature radius.