Measurement System of the Background Proton in DeeMe Experiment at J-PARC

In particle physics, various theories beyond the standard model predict the existence of the –e conversion process, but it remains undetected due to its low probability. The DeeMe experiment proposed at the J-PARC Material Life Science Facility is designed to detect the –e conversion process by using the muon-production target. During the DeeMe experiment, to distinguish the –e event signal from a background, less than one proton per hour should arrive from the main beam after a few hundreds of nanoseconds. We designed a new measurement system to confirm that such a low background is attained. A simulation indicates that the new system is sufficiently sensitive to detect the delayed protons.