Muon g-2/EDM Experiment at J-PARC

At J-PARC of Japan, a new, very different approach is in progress to measure the magnetic moment anomaly g-2 and the electric dipole moment(EDM) of the muon. Currently, there is a larger than 3 sigma discrepancy between the Standard Model prediction and the experimental value for g-2. New experiments for muon g-2 aims to reduce experimental errors by at least factor 3 from the previous 0.46 ppm. The new method at J-PARC involves muons orbiting in a pure magnetic field without any focusing electric field. This requires a muon beam of low emittance which can be achieved by stopping the secondary muon beams and re-accelerating them. This releases the constraint on the so-called magic momentum and makes it possible for a compact muon storage. The surface muons from pion decay are collected and stopped inside the silica aerogel target, where they form neutral muonium, which diffuses out to vacuum with only thermal motion. An external laser then ionizes the neutral muonium to have muons back at low emittance for re-acceleration to 300 MeV/c. The accelerated muons are injected into storage magnet for observation of the spin precession. The direction of the muon spin can be determined by decay positrons with relatively high energy. The decay positrons will be detected and their trajectories are reconstructed by silicon detectors in the shape of vanes inside the muon storage area. The magnetic moment anomaly g-2 can be measured by the additional spin precession with respect to the momentum of the muon, while up-down asymmetry of the high energy positrons is sensitive to the EDM. The stopping and re-accelerating muon beams necessitate a considerable amount of R&D and progresses are made at various components of the experiment. The uniformity and stability of the storage magnetic field necessary for the pursued precision also require some new idea. The presentation will be focused on the overview, current status and future prospects for J-PARC muon g-2/edm experiment.