COMET and DeeMe

Mu-e conversion search at J-PARC COMET Target sensitivity 10 C.L. using aluminum target – SINDRUM II 7x – MEG 2.4x J-PARC high intensity beam to produce pion/muon – ~2  sec pulse-to-pulse – 8GeV, 50kW Series of SC magnets – capture pions – transport muons – analyze electron momenta Physics run start scheduled in

COMET Key Technologies SC magnets operational under high- radiation environment – SC wire with aluminum stabilizer – “Follow the path of least resistance” Curved spectrometer solenoid for momentum selection – Easier detector operation owing BG suppression “Purely” pulsed proton beam – Good extinction thanks to J-PARC precise beam control Detectors – Low-mass tracking system operational in vacuum – Electron calorimeter Curved solenoid to restrict low momentum BG from entering the detector J-PARC proton beam extinction measurement achieving 5x10 -7 level; further study in progress

Another mu-e conversion search at J-PARC DeeMe Process : μ - +(A,Z) → e - +(A,Z) A single mono-energetic electron 105 MeV Delayed ： ~1μS S.E.S for 2 years run No accidental backgrounds Physics backgrounds Muon Decay in Orbit (DIO) E e > MeV (BR: ) E e > MeV (BR: ) Beam Pion Capture π - +(A,Z) → (A,Z-1)* → γ+(A,Z-1) γ → e + e - Proton Muon Target Pion Production Pion -> Muon Muonic Atom Formation Prompt BG Prompt Kicker Low-P BG 105MeV/c Delayed Magnet Spectrometer e e   Low Energy main part: suppressed by the beamline. High Energy tail: Magnet Spectrometer (Δp < 0.3%) Main pulse: Kicker to reduce the detector rate. after-protons: Suppressed owing to the extremely small after-protons from J-PARC/RCS: R AP <