The electronics for the electron calorimeter of the COMET experiment

The goal of COMET experiment is to search for the coherent neutrinoless muon to electron conversion at the field of atomic nucleus. This process is strongly forbidden in the SM at level below 10 -50 .The goal of the COMET experiment is to reach unrivaled sensitivity of 3x10 -15 at the first stage and of 3x10 -17 at the final experiment. The background rate is extremely high, few MHz. The main criteria for selection of the useful events from the background ones is the energy of electron produced in an event. Hence, the Electron Calorimeter of the COMET experiment is used for measuring the energy of electrons and for events selection. It leads to the controversial requirements on the electronics to provide the fast response and low noise performance.For the Electron calorimeter a dedicated custom electronics has been developed. It includes front-end electronics, which implements a special technique of amplification and shaping for achieving a very low noise level along with fast response, and Pre-trigger electronics, which uses online signal processing for real-time determination of energy depositions with high resolution, thus providing a good selection of events by the deposited energy. The output signals shape of the analog electronics is determined by the decay time of LYSO scintillator, so the contribution from pileup is kept minimal as possible. The on-line energy resolution is comparable with off-line one and satisfies the experiment requirement of 5%