Mu anti-Mu 変換実験 ~MUWG in 熱海 ~

Mu anti-MuMu anti-Mu 変換実験変換実験~MUWG in ~MUWG in 熱海熱海 ~~

J-PARC MLFJ-PARC MLF ディビジョン ミュオディビジョン ミュオンン

河村　成肇河村　成肇

物質・生命科学実験施設物質・生命科学実験施設

中性子生成標的

ミュオン生成標的

中性子分光器

中性子分光器

ミュオン科学実験施設= 陽子ビームライン　＋ミュオンビームライン

第二期ミュオン施設建設第二期ミュオン施設建設崩壊ミュオンビームライン（第一期建設分）大立体角ミュオンビームライン（第二期）

表面ミュオン（ 30MeV/c ）に特化し、軸収束のビームラインで大立体角、高輸送効率を狙う。

汎用性の高い崩壊ミュオンビームライン正負ミュオン（ 30-120MeV/c ）の輸送

大立体角ミュオンビームライン大立体角ミュオンビームライン

大立体角ビーム実験エリア

ミュオンビーム強度ミュオンビーム強度

崩壊ミュオンビームライン（１ＭＷ時）崩壊ミュオンビームライン（１ＭＷ時） 30MeV/c30MeV/c 3×103×1077 ++// 秒秒 6×106×1055 --// 秒秒 60MeV/c60MeV/c 5×105×1066 ++// 秒秒 1×101×1066 --// 秒秒 120MeV/c120MeV/c 2×102×1077 ++// 秒秒 1×101×1077 --// 秒秒

大立体角ミュオンビームライン（第二期大立体角ミュオンビームライン（第二期計画）計画） 30MeV/c30MeV/c 5×105×1088 ++// 秒秒 1×101×1077 --// 秒秒

大立体角ビームラインによる高強度化大立体角ビームラインによる高強度化

物理のイントロ物理のイントロ Lepton Flavor Violation (LFV)Lepton Flavor Violation (LFV)

||LLii| = 1| = 1

||LLii| = 2| = 2

e

eee

e conversion

Mu Mu conversion

e e

NuFact’00 青木

モデルモデル

(a) doubly charged Higgs boson, (b) heavy Majorana neutrinos, (c) a neutral scalar, e.g., a supersymmetric τ-sneutrino, or (d) a bileptonic flavor diagonal gauge boson

L. Willmann, et al. Phys. Rev. Lett. 82 (1999) 49-52

NuFact’00 青木

PSIPSI での実験での実験 SetupSetup

Surface muon (26 MeV/c)

N 8106 /s

Beam Time: 1290 hours

NMu 5.6 1010

L. Willmann, et al. Phys. Rev. Lett. 82 (1999) 49-52

NuFact’00 青木

PSIPSI での実験での実験

PMM

8.31011 (90%C.L.)

NBG 1.7

Bhabha scattering of e

eeee BR 3.4 105

ResultResult

NuFact’00 青木

Slow muonsSlow muons Slow muons : muons which are (re-)accelerated from Slow muons : muons which are (re-)accelerated from

the muons which are almost at a rest.the muons which are almost at a rest. Beam energy is tunable, and its spread is very small.Beam energy is tunable, and its spread is very small.

The range in the material is tunable down to sub The range in the material is tunable down to sub m.m. Emittance is very small. Emittance is very small.

Small sample can be used.Small sample can be used.

New application of New application of SR for thin filmsSR for thin films Possible application towards future muon/neutrino Possible application towards future muon/neutrino

sourcessources

NuFact’03 松田

Two methods to generate slow muon beamTwo methods to generate slow muon beam

Cryogenic moderator method (PSI)Cryogenic moderator method (PSI) Use a layer of solid rare gas as a moderator.Use a layer of solid rare gas as a moderator. Initial energy is 10-100eV, and its spread is around Initial energy is 10-100eV, and its spread is around

10eV.10eV. Time structure is determined by initial beam.Time structure is determined by initial beam.

Laser resonant ionization methodLaser resonant ionization method Obtain slow muons by ionizing thermal muoniums Obtain slow muons by ionizing thermal muoniums

emitted from a hot tungsten film.emitted from a hot tungsten film. Initial energy is around 0.2eV, and its spread is less Initial energy is around 0.2eV, and its spread is less

than 1eV. than 1eV. Time structure is determined by laser timing.Time structure is determined by laser timing. Gives better time resolution for pulsed beam.Gives better time resolution for pulsed beam. Possible use for Mu anti-Mu conversion experimentPossible use for Mu anti-Mu conversion experiment

as a sensitive detection method of anti-Mu and as a sensitive detection method of anti-Mu and background suppression.background suppression.

NuFact’03 松田

Slow-muon beam-line at RIKEN-RALSlow-muon beam-line at RIKEN-RAL

NuFact’03 松田

Slow-muon beam-line at RIKEN-RALSlow-muon beam-line at RIKEN-RAL

High purity Tungsten film (45m; 87mg/cm2)Tungsten degrader (20m; 39mg/cm2)

SUS foil (50m; 40mg/cm2)

Kapton foils

Ionizing Lasers

Main Chamber

Degrader chamber

(1x10 11 hPa)

(1x10 hPa)

surface muons

slow muons

Port 3 beam line(1x10 hPa)

NuFact’03 松田

Efficiency of slow muon generationEfficiency of slow muon generation

Observed slow muon signal : Observed slow muon signal : 3.3 3.3 /sec/sec

(MCP efficiency 66%) (MCP efficiency 66%) 5.0 5.0 /sec/sec

(Decay in flight 43%)(Decay in flight 43%) 8.6 8.6 /sec/sec

(Transport efficiency unknown. assume 100%) (Transport efficiency unknown. assume 100%)

>8.6 >8.6 /sec at the source/sec at the source

Initial surface muon beam : 1.0x10Initial surface muon beam : 1.0x1066 /sec /sec

Efficiency 8.6/1.0x10Efficiency 8.6/1.0x1066 = 8.6x10 = 8.6x1066 (still low…) (still low…)

NuFact’03 松田

Future plan for slow muonFuture plan for slow muon Beam studyBeam study

Beam profile measurement ( Segmented MCP, Slit, emittance measureBeam profile measurement ( Segmented MCP, Slit, emittance measurement)ment)

SR studySR study Scintillator telescopes installation around the MCP chamber.Scintillator telescopes installation around the MCP chamber. Helmholtz coil installationHelmholtz coil installation

Thinking of fundamental physics…Thinking of fundamental physics… MuMuanti-Mu conversion experiment : double coincidence between laser iranti-Mu conversion experiment : double coincidence between laser ir

radiation and anti-Mu detection will reduce background significantly.radiation and anti-Mu detection will reduce background significantly. PSI experiment accumurated 5.7x10PSI experiment accumurated 5.7x101010 muonium decays. We need signifi muonium decays. We need signifi

cant improvement of slow muon yield.cant improvement of slow muon yield. Muon intensity improvement : J-PARC, new proton driver, new desiMuon intensity improvement : J-PARC, new proton driver, new desi

gn of capture channel.gn of capture channel. Muon to muonium conversion improvement : cyclotron trapMuon to muonium conversion improvement : cyclotron trap

NuFact’03 松田

Cyclotron trapCyclotron trap PSI & LEAR applicationPSI & LEAR application

Winding up the range path of stopping particles inside a weaWinding up the range path of stopping particles inside a weak focusing cyclotron field. It has been used for producing low k focusing cyclotron field. It has been used for producing low energy negative muons beams, pions and anti-protons.energy negative muons beams, pions and anti-protons.

Moderator can be gas (typically ~1mbar Hydrogen), or thin Moderator can be gas (typically ~1mbar Hydrogen), or thin metal foils. metal foils.

Application for positive muons have been limited because of Application for positive muons have been limited because of high capture rate of electron.high capture rate of electron.

Cyclotron trap + laser ionizationCyclotron trap + laser ionization Can expect increase of muon stopping density at the near-suCan expect increase of muon stopping density at the near-su

rface of Tungsten foil.rface of Tungsten foil. We will lose muon polarization. This will limit application for We will lose muon polarization. This will limit application for

SR, but is good for Mu SR, but is good for Mu anti-Mu oscillation experiment. anti-Mu oscillation experiment. Recover muon polarization with polarized laser light?Recover muon polarization with polarized laser light?

NuFact’03 松田

まとめまとめ J-PARC MLFJ-PARC MLFの大立体角ミュオンビームラインをの大立体角ミュオンビームラインを使い、使い、 Mu-antiMuMu-antiMu実験ができる。超低速ミュオン実験ができる。超低速ミュオンビームラインとほとんど同じ装置で逆のビームラインとほとんど同じ装置で逆の polaritypolarity。。

5×105×1088 surface surface ++/s ×10/s ×10-5-5 ( (++→slow →slow ++))5×105×101010 Mu/0.5y Mu/0.5y（（ 2×102×1077 Mu/s=2×10 Mu/s=2×101212 Mu/d Mu/d））

現状現状 (1MW)(1MW)でも、半年程度ででも、半年程度で PSIPSIと同程度の統計。と同程度の統計。LaserLaserとの同期で散乱からくるとの同期で散乱からくる BGBGはなし。ただし、はなし。ただし、in-flightin-flightでのでの -e-e崩壊などが問題になる？崩壊などが問題になる？

Mu-antiMuMu-antiMu変換はいつ起こる？変換はいつ起こる？ LaserLaserを打つタイを打つタイミングは？ミングは？