Mu3e - Search for the Decay μ → eee at PSI

Responsible Professors

C. Grab, R. Wallny

Status

Approved

Description

Within the standard model of particle physics, the decay of muons into three electrons "mu --> eee" is only allowed at an extremely low and unmeasurable rate, because it violates the lepton flavour number symmetry.

Any observation of such a process would therefore without any doubt point to the existence of physics beyond the standard model of particle physics. This high-sensitivity experiment is complementary to existing other search experiments and to the experiments at the LHC. This experiment aims to reach a sensitivity of one in 10¹⁶ muon decays, which is a four order of magnitude improvement over the previous results.

The experiment is being built for a first phase of measurements in the years 2017-2018. The PSI scientific review committee has approved this project as a scientifically highly relevant addition to the PSI muon physics program. It will become one of the particle physics flagship experiments at PSI, complementing the Mu-egamma experiment. The Mu3e collaboration is a cooperation of Univ. of Heidelberg, Univ. of Zurich, ETH Zurich, Univ. of Geneva and PSI.

The technologies chosen include silicon detectors for the momentum measurements of charged particles and a scintillating fibre detector for high-resolution time-of-flight measurements, aiming at a few hundred picosecond time resolution. This fibre detector will be of cylindrical geometry of about 6 cm radius and about 36 cm length.

IPP  participates in the development and in the construction of all aspects of this scintillating fibre detector. This includes development of fibre geometry, photon detection, very fast signal processing, and data readout at very high rates of several MHz per channel. First prototypes of the detector components exist, however  the details still have to be optimized  and subsequently built. The fibre detector is a combined Swiss effort of ETHZ, PSI, UZH and UGe.