7予想される陽電子の時間分布 w 磁場中で、ミュオンのスピンは時間と共に歳差運動。 高エネルギーの陽電子数も同じ周波数で変化する。 高エネルギーの陽電子数も同じ周波数で変化する。p>200 MeV/c１年間(107sec)測定we+ decay time (sec)
8Expected time spectrum of me+nn decay EDMがあると歳差運動の軸が磁場方向から傾く崩壊陽電子が磁場方向に対して上下の非対称に生じるdm=2E-20 e・cmp>200 MeV/c１年間(107sec)測定wUp-down asymmetry∝EDMe+ decay time (sec)
9Collaboration (Contributors to CDR) 92 members ( …still evolving)25 Institutions: KEK, RIKEN, U-Tokyo, TRIUMF, BNL, PMCU, CYCRC-Tohoku, Osaka, Rikkyo, TITech, SUNYSB, RAL, UCR, UNM, Victoria7 countries: Czech, USA, Russia, Japan, UK, Canada, FranceThe stage-1 approved in IMSS PAC, and stage-1 recommended in IPNS PAC.
10Ultra-slow muons for g-2/EDM Pointing powerNo focusing field pT/p < MeV/cMomentum pT < 3 keV/cp = (3/2)1/2pT < 3.7 keV/cKinetic energy E < eVTemperature T < 750 K (2000 K )This condition could be relaxed if very-weak focusing is applied (hot-W would be ok too).IntensityStatistical uncertainty on aμ = 0.1 ppm (goal) 1013 muons/year 106 ultra-slow muon /secPolarizationFigure-of-Merit = NP250 100%
11Ultra-slow muons for g-2/EDM Requirements:40000 times more muons, andCooler muon than RIKEN-RAL (not mandatory)
12Ultra-slow muons for g-2/EDM Requirements:40000 times more muons, andCooler muon than RIKEN-RAL (not mandatory)170 times higher surface muon per spill at J-PARC H-line2.4 x 104/spill 400 x 104/spill (25 spill/sec)Room temperature target (hot tangsten silica aerogel?)2000K (15keV/c) 300K (2.3keV/c)100 times intense Ly-α laser1mJ 100mJ4x104 ultra-cold muon/spill with p=2.3keV/c
13Room-temperature muonium emitter Silica powders (SiO2)Structure : network of SiO2 grain Large surface area.Known to be a good Mu emitter at room temp.Not self-standing difficulty in laser ionization.Silica aerogelSimilar structure of SiO2 grain-network.Self-standing!Control of density and thicknessOnly few (and old) data availableVacuum yield and space-time distributions with their density dependence were measured at TRIUMF.MaterialAerogelSilica PlateDensity27mg/cc50mg/cc99mg/cc180mg/cc2.2g/ccThickness7.8mm4.7mm2.4mm2.3mm0.96mm
14Space-time distribution of Mu Reconstructed Mu decay vertex position● Aerogel 27mg/cc● Silica platePreliminarySilica plate data is used to estimate the background distribution.Enhancement in aerogel data is due to Mu emission in vacuum.Mu signals are observed in all aerogel densities.Distance from target surfaceTarget surface
15Back of envelope estimate of efficiencies from surface to ultra-cold muons Beer, et al.(89, TRIUMF)Woodle, et al.(88, PSI)S1249(2011, TRIUMF)Mills, et al.(86, KEK-MSL)StragglingPreliminaryRequired yield : 1.E+6/sa factor of 8 behind ?
16Prospects on Mu target developments AerogelsSqueeze as much information as possible from S1249 dataDensity dependence, space-time distributions etc…More surface areaPorous structure?New PSI work on meso-porous Silica (arXiv: )Micro-drilled W-foil10μm-pitch drilled foil was tried at RIKEN-RALStarted R&D for 1μm pitch for further gainSurface conditionsW coated with alkali-metal (Na, Cs)By Prof. Y. Miyake, Prof. Y.Nagashima et al.wikipediaRIKEN-RAL
17Laser development and ionization test Laser development at RIKENOmega-1Fiber Laser SystemSolid State AmplifierNon-linear frequency converterOmega-2SLM Seeder1st and 2nd Non-linearamplification2-photon resonant 4-wave mixing in Kr cellIonization test at RIKEN-RALImproved laser systemstable, more freedom of adjustmentsNew beam line controlsHeater system refurbishedData being collected (March, May-June)To be tested and installed to U-line in 2012
18まとめ A new muon g-2/EDM experiment at J-PARC: Ultra-slow muons Off magic momentum + compact g-2 ringComplementary to FNAL g-2Start in 2016Ultra-slow muonsThe key technology to realize required beamTRIUMF S1249 studies Mu emitting materials at room temp.Mu from hot W at J-PARC in progressIonization test with improved laser system is in progress at RIKEN-RAL.Intense Ly-α laser being developed in close collaboration with U-line developers.
22J-PARC Material and Life science Facility S-LineU-LineMaterial and Life ScienceFacilityD-LineBird’s eye photo in Feb. 2008
23TRIUMF-S1249 : search for muonium emitting material at room temp. Goals are to examine materials at room temp.Muonium production rateMuonium distribution in vacuumMCPm+e+TRIUMF-M15 beamlinee-Decay in vacuumm+MuoniumTargetMWDCNaIe+