The Mu2e experiment at Fermilab searches for the charged-lepton flavor violating neutrino-less conversion of a negative muon into an electron in the field of a aluminum nucleus. The baseline calorimeter configuration consists of two disks, each one made of ∼ 700 undoped CsI crystals read out by two large area UV extended Silicon Photomultipliers (SIPM). These crystals emit at 310 nm with a large light yield (30 pe/MeV) when coupled in air to the SIPMs and provide a fast response and accurate timing having a time emission of τ ∼ 20 ns. These crystals match the requirements for stability of response, high resolution and radiation hardness. SIPM signals are amplified, shaped and then read out through 200 msps waveform digitizers optically connected to the DAQ system. We present the calorimeter design,  the experimental tests and the simulation carried out to prove the validity of the chosen configuration. In particular, we will summarise the results of the test beam with electron beams in the energy range between 80 and 140 MeV and the irradiation program carried out both with crystals and SiPM.

Contribution to CALOR 2016 proceedings: http://arxiv.org/abs/1606.05448

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