The MEG II experiment is an upgrade of the MEG experiment which searched for the charged lepton flavor violating decay of muon, μ→eγ. The target sensitivity of MEG II experiment is 4 × 10−14. The liquid xenon (LXe) detector was used to detect γ-ray from the signal decay, and its performance will be upgraded in MEG II. To achieve the higher granularity and uniformity of the scintillation readout, 216 photomultiplier tubes (PMTs) on the γ-ray entrance face has been replaced with 4092 Multi-Pixel Photon Counters (MPPCs). In this replacement, a large area VUV-MPPC is used which was newly developed in collaboration with Hamamatsu Photonics K.K. The performance of this MPPC was measured in LXe. Photon detection efficiency for LXe scintillation light was confirmed to be over 15%. Mass production of MPPC was performed and it was successfully installed to the detector. Detector commissioning is now ongoing towards the pilot run at the end of this year.
