Study of High Intensity Stopping Muon Beams and Experimental Apparatuses for μィイD1+ィエD1 →eィイD1+ィエD1+γ Experiment

1999 Fiscal Year Final Research Report Summary

• Project/Area Number: 10041128
• Research Category: Grant-in-Aid for Scientific Research (B).
• Allocation Type: Single-year Grants
• Section: 一般
• Research Field: 素粒子・核・宇宙線
• Research Institution: High Energy Accelerator Research Organization
• Principal Investigator: MAKI Akihiro Institute of Particle and Nuclear Studies, High Energy Accelerator Research Organization, Professor, 素粒子原子核研究所, 教授 (40044755)
• Co-Investigator(Kenkyū-buntansha): HARUYAMA Tomiyoshi Institute of Particle and Nuclear Studies, High Energy Accelerator Research Organization, Associate Professor, 素粒子原子核研究所, 助教授 (90181031) ; SUGIMOTO Yasuhiro Institute of Particle and Nuclear Studies, High Energy Accelerator Research Organization, Research Associate, 素粒子原子核研究所, 助手 (70196757) ; KUNO Yoshitaka Institute of Particle and Nuclear Studies, High Energy Accelerator Research Organization, Associate Professor, 素粒子原子核研究所, 教授 (30170020)
• Project Period (FY): 1998 – 1999
• Keywords: Lepton flavor violation / Muon decay / Liquid xenon / scintillation calorimeter / Pulse tube refrigerator

Research Abstract

An experiment was designed to improve and identify a lepton flavor number violating decay process, a muon decay into a positron and a photon. The process is severely prohibited by the standard model of the elementary particle, and the identification of the process gives us a signal of the new world of the particle physics, beyond the standard model.
The concept of the experiment is based on two innovative ideas, liquid xenon scintillation calorimeter for measuring energy, position and timing of photons and COBRA spectrometer for measuring momentum of positrons.
Several development programs have been carried out to made the above experiment possible. Firstly, a new phtomultiplier tube was developed to detect the scintillation photons(wavelength of 175 nm) from liquid xenon at the low temperature of -100℃. A small test calorimeter with 32 photomultiplier tubes was built and used to confirm the expected performances of the liquid xenon calorimeter. Secondly, a pulse tube refrigerator was developed to directly liquefy the large amount of xenon gas.
Together with other studies, and experimental proposal was written and submitted to Paul Sherrer Institute, Switzerland in May 1999. The proposal was accepted in July, 1999 by the Institute. Currently, further details are being studied.