The MEG experiment

Muon to Electron and Gamma experiment at PSI

THE MUON TO ELECTRON AND GAMMA EXPERIMENT AT PSI

The MEG experiment is searching for the Lepton Flavour Violating (LFV) decay of the muon: μ → eγ. With the established fact of neutrino flavour mixing and its finite mass, the Standard Model is now believed to be an effective theory and a low-energy manifestation of a more fundamental theory at higher energies could be observed. Several classes of models beyond the SM, such as supersymmetry, grand-unification, extra-dimensions or models with heavy right-handed neutrinos, for the branching ratio of LFV decays such as μ → eγ in the range of 10-11 to 10-15, thus validating that MEG search is complementary to that of high-energy TeV-scale accelerator searches for “New Physics”.

The quest for μ → eγ dates back more than sixty years to the pioneering efforts of Hinks & Pontecorvo in 1948, who first searched for a signal in cosmic-ray decays.  MEG is searching now this decay at the most intense muon source in the world at PSI (CH), looking at the muon decay products at a rate of 3x107 per second. The electron energy and decay time is detected within a magnetic spectrometer in which are mountes Drift Chambers and 60 ps resolution Timer Counters (Responsability of Genoa Group). The gamma is is detected by about 3 tons liquid Xe detector.  All the 2000 readout channels from the detectors are fully digitised at about 2 GB/s. The experiment has completed in 2013 the first phase and the most updated upper limit on μ → eγ is 5.7x10-13 respect to the  muon normal, 20 times lower than the previous limit.

DIFI research group: 
Italian Research Institutes: 
Istituto Nazionale di Fisica Nucleare
Via Dodecaneso 33
16146, Genova
Italia
Tel: +39 010 353 6267
Fax: +39 010 314 218