The Mu2e crystal calorimeter

The Mu2e Experiment at Fermilab will search for coherent, neutrinoless conversion of negative muons into electrons in the field of an aluminum nucleus. The dynamics of this process is well modelled by a two-body decay, resulting in a mono-energetic electron with an energy slightly below the muon rest mass (∼104.967 MeV). If no events are observed in three years of run- ning, Mu2e will set an upper limit on the ratio between the conversion rate and the capture rate Rμe ≤ 6 × 10−17 (@ 90% C.L.). This will improve the current limit of a factor of 104 over previous experiments The experiment complements and extends the current search for μ → eγ decay at MEG as well as the direct searches for new physics at the LHC. Indeed, such a charged lepton flavor-violating reaction probes new physics at a scale inaccessible with direct searches at either present or planned high energy colliders. We briefly present the physics motivation for Mu2e, the current status of the experiment and the design of the muon beamline and the detector, devoting particular attention to the R&D phase, simulation and test carried out to prove the validity of the electromagnetic calorimeter configuration.