Development of PPDs to detect scintillation light from liquid xenon

MEG experiment searches for new physics like SUSY-GUT/SUSY-seesaw through the lepton flavor violating μ → eγ decay. The current MEG experiment utilizes 846 2 inch PMTs in order to detect scintillation light in 900 ℓ liquid xenon gamma-ray calorimeter. R&D of Pixelated Photon Detector (PPD) have been actively performed in many different fields as a new novel silicon photon detector, and we started developing a new type of PPD which is sensitive to liquid xenon scintillation light (175nm wavelength) as one of possible candidates of MEG detector upgrade plan in collaboration with Hamamatsu Photonics. Basic characteristics of these samples such as photon detection efficiency(PDE), gain, dark rate, cross talk, after pulse, pulse rise time/fall time, timing resolution, linearity etc. are being measured in a small setup in PSI with 2 ℓ liquid xenon, refrigerator, and
²⁴¹
Am source. Preliminary result already shows 10% PDE in liquid xenon. These results and further optimization of MPPC parameters as well as possible prototype plan are described here.