Speaker
Description
The MEG II experiment searches for new physics like SUSY-GUT/SUSY-seesaw through the lepton flavor violating mu+->e+ gamma with ten times better sensitivity than the MEG expriment( B(mu+ -> e+ gamma) < 4.2x10-13 at 90% CL in 2016). Because the sensitivity of the MEG experiment was already limited by accidental background, the MEG detector was upgraded to realize one order of magnitude better sensitivity. Since the MEG and the MEG II experiment uses the 900l liquid xenon to detect 52.8 MeV gamma-rays, the photo sensors must be sensitive to the VUV light (175nm) and be operational at 165K. The MEG experiment utilized 846 2inch PMTs, and the MEG II experiment replaced 216 2inch PMTs on the gamma incident face with 4092 15x15mm2 MPPCs (SiPMs produced by Hamamatsu) to improve the energy, position resolutions. The MEG II experiment has started the physics run in 2021, and the first result was published in October 2023. In this talk, after the MEG II experiment and the initial results are briefly introduced, the SiPM characteristics including the calibration methods and the stabilities will be summarized based on the operation experience during the MEG II physics run for a few years.
