Speaker
Description
Plans for a future experiment to search for $\mu^+\to e^+\gamma $ are now under discussion. To achieve $\mathcal{O}(10^{-15})$ sensitivity, developing a photon detector with good resolutions and high rate capability is crucial. Therefore, we are considering using a pair spectrometer for photon detection, which offers better resolution and higher rate capability than a calorimeter. The principle of a photon pair spectrometer involves converting photons into electron-positron pairs in a converter and measuring the daughter particles' momentum, position, and timing.
In order to achieve the best resolution with a reasonable conversion probability, we will use an active material for the converter, which enables the measurement of the energy deposit in the converter. The performance of a converter prototype, consisting of a LYSO scintillator and SiPM for the readout, was tested in a 3 GeV electron beam test.
The results show that an active converter with LYSO achieved a good time resolution of 30 - 35 ps and detection of several thousand photoelectrons, surpassing the requirements for an active converter (40 ps and 700 photoelectrons). Therefore, we conclude that LYSO is a suitable material for an active converter of the photon pair spectrometer of the next generation $\mu^+\to e^+\gamma $ search experiment.
