Performance of the Liquid Xenon Scintillation Detector for the MEG Experiment

A large-volume liquid xenon (LXe) scintillation detector has been developed for the MEG experiment, which will seek evidence for the lepton flavor violating process, mu rarr egamma with a branching ratio sensitivity smaller than 10^-13. A prototype detector with 100 L LXe was constructed to demonstrate that the performance of the proposed full-scale detector fulfills the requirements for the MEG experiment. New photomultipliers with a higher quantum efficiency and better performance under high rate environment were recently developed and employed in the prototype detector. The performance of the detector was measured with high-energy monochromatic photons from pi⁰ decays produced in the charge exchange (CEX) process. We obtained an energy resolution of 1.2plusmn0.1 % in sigma on the right side of the peak for the 55 MeV photons. The timing resolution was also measured to be 65 psec in sigma.