Fourth-year undergraduate students conducted muon decay observation experiments using a muon beam at the Materials and Life Science Experimental Facility (MLF) in the Japan Proton Accelerator Research Complex (J-PARC). It is well known that the phase space of the positrons produced by muon decay depends on the muon spin direction, and its spectrum is expressed by a function of four parameters (Michel parameters). The students focused on two of these parameters, ρ and ξ. Those parameters appear in the energy spectrum and in the spectrum of the angular difference from the muon spin direction, respectively. The students devised experiments by themselves to measure these parameters, constructed detectors, and calculated the expected data. This was the first time for the students to conduct experiments at the beamline, so there were some difficulties. Eventually, they could complete the measurements successfully. They are now analyzing the acquired data. The analysis results will be reported at the graduation thesis presentation (see here for the announcement).

We would like to express our gratitude for the supports from the Accelerator Science internship program at KEK and the J-PARC MLF.