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ミュオン g-2/EDM の精密測定 2012年5月19日 三部勉( KEK ) J-PARC muon g-2/EDM collaboration 1.

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Presentation on theme: "ミュオン g-2/EDM の精密測定 2012年5月19日 三部勉( KEK ) J-PARC muon g-2/EDM collaboration 1."— Presentation transcript:

1 ミュオン g-2/EDM の精密測定 2012年5月19日 三部勉( KEK ) J-PARC muon g-2/EDM collaboration 1

2 ミュオン異常磁気能率 g-2 2 標準理論の予測から 3 σ のズレ 標準理論の予測から 3 σ のズレ + ++ …      = a μ = (g-2)/2 = + EW + Hadronic + BSM ? QED HLMNT11 : J.Phys.G38:085003,2011 野村大輔氏(東北大)の資料より 〜 BNL E821 (0.5ppm) 新たな実験で検証! 磁気能率 : 磁場に対する粒子(スピン)の応答 ミュオンの g 因子はディラック方程式では2であるが、量子ループによって2からずれる。

3 Dark matter contribution? 宇宙観測実験 – 暗黒物質が必要 – 宇宙の構成物質のうち22% を占める。 – その正体は依然として不明 WIMPS (SUSY LSP) Axion … ダークセクター – 新しいゲージ粒子 暗黒 Z ボソン (Z d ) – Z-Z d 混合によって測定にかか る可能性がある。 電子陽電子衝突 パリティ非保存電子散乱 K/B 稀崩壊 g-2 3 Davoudiasl, Lee, Marciano arXiv:

4 g-2/EDM の測定 4 一様磁場中でミュオンが円運動する場合、 スピンは g-2 分だけ、ミュオンより早く回転する。 この余剰な回転周期を測定して a μ (= (g-2)/2 ) を求める。 一般には電場が磁場に見える項や EDM によってもスピンは 回転する。 BNL E821 approach γ=30 (P=3 GeV/c) J-PARC approach E = 0 電場ゼロの環境にすることで、 運動量に寄らず、 g-2 と EDM を測定できる

5 J-PARC muon g-2/EDM 実験 5 物質生命科学実験施設 (MLF) ミュオン基礎物理ビームライン( H-Line ) 極冷 μ + ビーム : 強度 10 6 /sec 運動量 300 MeV/c (γ = 3) σ(p T )/p < 偏極度 >50% 陽子ビーム 蓄積磁石・検出器 極冷 μ + ビーム 、ミュオン蓄積磁石(3 T ) 、陽電子飛 跡検出器 1. 蓄積磁石上側から極冷 μ + ビーム入射 2. パルスキッカーで磁石中心蓄積領域に静止し蓄積 3. 崩壊 μ +  e + νν で生じる陽電子を陽電子飛跡検出器で 33μs ( 5x ミュオン寿命)の間測定 1. 蓄積磁石上側から極冷 μ + ビーム入射 2. パルスキッカーで磁石中心蓄積領域に静止し蓄積 3. 崩壊 μ +  e + νν で生じる陽電子を陽電子飛跡検出器で 33μs ( 5x ミュオン寿命)の間測定 概要+極冷 μ (三部) 入射・磁石 (飯沼) 測定器(上野)

6 入射、蓄積、陽電子検出 6 ミュオンビーム入射位置 Magnet coil (3T) detector kicker mm Spiral injection Anti-Helmholtz-type kicker (Pulse kick to stop spiral) Positron tracker ν ν e+e+ ミュオン蓄積磁石

7 予想される陽電子の時間分布 7 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。  e + decay time (sec) p>200 MeV/c 1年間 (10 7 sec) 測定

8 d  =2E-20 e ・ cm Expected time spectrum of   e + decay 8 Up-down asymmetry e+ decay time (sec) 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 ∝ EDM  p>200 MeV/c 1年間 (10 7 sec) 測定

9 Collaboration (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, Victoria 7 countries: Czech, USA, Russia, Japan, UK, Canada, France 9 The stage-1 approved in IMSS PAC, and stage-1 recommended in IPNS PAC.

10 Ultra-slow muons for g-2/EDM Pointing power Pointing power – No focusing field  p T /p < 10 MeV/c – Momentum p T < 3 keV/c p = (3/2) 1/2 p T < 3.7 keV/c – Kinetic energy E < eV – Temperature T < 750 K (2000 K ) This condition could be relaxed if very-weak focusing is applied (hot-W would be ok too). Intensity Intensity – Statistical uncertainty on a μ = 0.1 ppm (goal)  muons/year  10 6 ultra-slow muon /sec Polarization Polarization – Figure-of-Merit = NP 2 – 50  100% 10

11 Ultra-slow muons for g-2/EDM Requirements: times more muons, and Cooler muon than RIKEN-RAL (not mandatory)

12 Ultra-slow muons for g-2/EDM 12 Requirements: times more muons, and Cooler muon than RIKEN-RAL (not mandatory) 170 times higher surface muon per spill at J-PARC H-line 2.4 x 10 4 /spill  400 x 10 4 /spill (25 spill/sec) 170 times higher surface muon per spill at J-PARC H-line 2.4 x 10 4 /spill  400 x 10 4 /spill (25 spill/sec) 100 times intense Ly-α laser 1  J  100  J 100 times intense Ly-α laser 1  J  100  J Room temperature target (hot tangsten  silica aerogel?) 2000K (15keV/c)  300K (2.3keV/c) Room temperature target (hot tangsten  silica aerogel?) 2000K (15keV/c)  300K (2.3keV/c)

13 MaterialAerogel Silica Plate Density27mg/cc50mg/cc99mg/cc180mg/cc2.2g/cc Thickness7.8mm4.7mm2.4mm2.3mm0.96mm Room-temperature muonium emitter 13 Silica powders (SiO 2 ) Structure : network of SiO 2 grain  Large surface area. Known to be a good Mu emitter at room temp. Not self-standing  difficulty in laser ionization. Silica aerogel Similar structure of SiO 2 grain-network. Self-standing! Control of density and thickness Only few (and old) data available Vacuum yield and space-time distributions with their density dependence were measured at TRIUMF.

14 Space-time distribution of Mu Silica 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. 14 ● Aerogel 27mg/cc ● Silica plate Distance from target surface Reconstructed Mu decay vertex position Preliminary Target surface

15 Back of envelope estimate of efficiencies from surface to ultra-cold muons 15 Beer, et al. (89, TRIUMF) Woodle, et al. (88, PSI) S1249 (2011, TRIUMF) Mills, et al. (86, KEK-MSL) Required yield : 1.E+6/s a factor of 8 behind ? Preliminary Straggling

16 Prospects on Mu target developments Aerogels – Squeeze as much information as possible from S1249 data Density dependence, space-time distributions etc… More surface area – Porous structure? New PSI work on meso-porous Silica (arXiv: ) – Micro-drilled W-foil 10μm-pitch drilled foil was tried at RIKEN-RAL Started R&D for 1μm pitch for further gain Surface conditions – W coated with alkali-metal (Na, Cs) By Prof. Y. Miyake, Prof. Y.Nagashima et al. 16 wikipedia RIKEN-RAL

17 Laser development and ionization test Laser development at RIKEN –Omega-1 Fiber Laser System Solid State Amplifier Non-linear frequency converter –Omega-2 SLM Seeder 1 st and 2 nd Non-linear amplification –2-photon resonant 4-wave mixing in Kr cell Ionization test at RIKEN-RAL – Improved laser system stable, more freedom of adjustments – New beam line controls – Heater system refurbished – Data being collected (March, May-June) 17 To be tested and installed to U-line in 2012

18 まとめ A new muon g-2/EDM experiment at J-PARC: – Off magic momentum + compact g-2 ring – Complementary to FNAL g-2 – Start in 2016 Ultra-slow muons – The key technology to realize required beam – TRIUMF S1249 studies Mu emitting materials at room temp. – Mu from hot W at J-PARC in progress – Ionization test with improved laser system is in progress at RIKEN-RAL. – Intense Ly-α laser being developed in close collaboration with U-line developers. 18

19 19

20 Projected schedule 20 Now CDR submitted Stage-1 approved TDR submmision Stage-2 request?

21 BNL, FNAL, and J-PARC 21

22 Bird’s eye photo in Feb J-PARC Material and Life science Facility U-Line D-Line S-Line

23 ++ Muonium Target Muonium Target TRIUMF-S1249 : search for muonium emitting material at room temp. TRIUMF-M15 beamline Goals are to examine materials at room temp.  Muonium production rate  Muonium distribution in vacuum Goals are to examine materials at room temp.  Muonium production rate  Muonium distribution in vacuum e-e- e+e+ e+e+ MWDC NaI ++ Decay in vacuum


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