1. ２０１２年５月１９日 三部勉（KEK） J-PARC muon g-2/EDM collaboration

2. ミュオン異常磁気能率 g-2 + EW aμ = (g-2)/2 = + Hadronic + BSM ? ＝ ＋ ＋ ＋ … QED
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。
aμ = (g-2)/2 =
+ EW
+ Hadronic
+ BSM ? m ＝ ＋ m m ＋
＋　… m m
QED
標準理論の予測から
３σのズレ
〜BNL E821 (0.5ppm)
新たな実験で検証！
HLMNT11 : J.Phys.G38:085003,2011
野村大輔氏（東北大）の資料より

3. Dark matter contribution?
Davoudiasl, Lee, Marciano
arXiv:
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 (Zd)
Z-Zd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

4. g-2/EDMの測定 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aμ (= (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 概要＋極冷μ （三部） 極冷 μ+ ビーム 入射・磁石 （飯沼）
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　　106/sec
運動量　300 MeV/c (γ = 3)
σ(pT)/p < 10-3　
偏極度　>50%
概要＋極冷μ
（三部）
陽子ビーム
極冷 μ+ ビーム
、ミュオン蓄積磁石（３T）
蓄積磁石・検出器
入射・磁石
（飯沼）
蓄積磁石上側から極冷 μ+ ビーム入射
パルスキッカーで磁石中心蓄積領域に静止し蓄積
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
、陽電子飛跡検出器
測定器（上野）

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

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/c
１年間(107sec)測定 w
e+ decay time (sec)

8. Expected time spectrum of me+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・cm
p>200 MeV/c
１年間(107sec)測定 w
Up-down asymmetry
∝EDM
e+ decay time (sec)

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
The stage-1 approved in IMSS PAC, and stage-1 recommended in IPNS PAC.

10. Ultra-slow muons for g-2/EDM
Pointing power
No focusing field  pT/p < MeV/c
Momentum pT < 3 keV/c
p = (3/2)1/2pT < 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
Statistical uncertainty on aμ = 0.1 ppm (goal)
 1013 muons/year
 106 ultra-slow muon /sec
Polarization
Figure-of-Merit = NP2
50 100%

11. Ultra-slow muons for g-2/EDM
Requirements:
40000 times more muons, and
Cooler muon than RIKEN-RAL (not mandatory)

12. Ultra-slow muons for g-2/EDM
Requirements:
40000 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 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 laser
1mJ 100mJ
4x104 ultra-cold muon/spill with p=2.3keV/c

13. Room-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 aerogel
Similar structure of SiO2 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.
Material
Aerogel
Silica Plate
Density
27mg/cc
50mg/cc
99mg/cc
180mg/cc
2.2g/cc
Thickness
7.8mm
4.7mm
2.4mm
2.3mm
0.96mm

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

15. Back 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)
Straggling
Preliminary
Required yield : 1.E+6/s
a factor of 8 behind ?

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.
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
1st and 2nd 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)
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 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.

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

21. BNL, FNAL, and J-PARC

22. J-PARC Material and Life science Facility
S-Line
U-Line
Material and Life Science
Facility
D-Line
Bird’s eye photo in Feb. 2008

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