Particle Physics Seminar

All the known processes involving charged leptons, such as electron, muon and tau, conserve lepton flavor. Thus, it is embedded in the Standard Model (SM) a priori, and the processes violating the flavor invariance of the charged leptons (charged lepton flavor violation: CLFV) are totally forbidden in the SM. There might be a higher order effect coming from the neutrino oscillation, but the amplitude is suppressed by a GIM-like mechanism to the level of 10-50, which is far beyond the experimental accessibility. On the other hand, there are numerous theoretical models giving predictions for the CLFV processes: SUSY-GUT, SUSY-Seesaw, extra dimension, and so on. A CLFV signal may be seen by experiment that improves the current experimental upper limit only a few orders of magnitudes. It is conceivable that the CLFV signal lies waiting to be discovered right under the current limit.
DeeMe collaboration had proposed a new experiment to search for the muon-electron conversion at J-PARC by using 3-GeV pulsed proton beam from a booster synchrotron (RCS). It utilizes muonic atoms formed in a primary proton target, and extracts 105-MeV/c electrons from the muon-electron conversion by using a large-acceptance secondary beamline. The number of muonic atoms formed in the primary target is estimated to be 1010/sec for 1 MW operation of the RCS. DeeMe aims to reach 10-14 of the single event sensitivity for silicon nuclei in a silicon-carbide production target. The detailed design of DeeMe is currently on going. It is relatively simple experiment compared to the other muon-electron conversion experiments proposed in J-PARC MR and Fermilab, and we aim to deliver the physics result within several years. The DeeMe beamline is designed so that it can be used for not only DeeMe but also other experiments such as muon g-2, muonium byperfine structure measurement and so on. Fruitful outcomes of the muon fundamental science will be expected from J-PARC in near future.