M. AokiTranslation of slides in 2010 JPS meeting (Okayama)

By K. Shimomura and M. Aoki

M. AokiA， T. EbiharaA， N. Kawamura ， Y. KunoA ， P. Strasser ，

N. NakadozonoA ， H. Nishiguchi ， K. Nishiyama ，T. NumaoB ， T. HikidaA ，

E. MatsushitaA ， S. Mihara ， Y. Miyake ， K. YoshimuraKEK ， Osaka U.A ， TRIUMFB

Measurement of Muonium Yield

MLF Beam Test• Measurement of the Yield of Muonic Atom.

• By measuring electrons from the decay of the muonic atom.

• The time spectrum of the electrons should be the same to that of the life time of μ- in carbon (2.0 μs).

• The momentum spectrum of the delayed electrons should be like that of Michel spectrum.

• Performed at D2 in J-PARC MLF

• 2009A0023: 3 days

• 2009A0032: 1 day

3

D2 Beam line at J-PARC MLF

D2 PortDesigned for the decay-muon　 maximum momentum: 120MeV/c→ can extract 105MeV/c electrons.

Muon Target

Proton Beam Neutron Target

Superconducting Solenoid

4

Surface muon extraction by D2 Beam line

Q1

-0.826

Q2

0.813

Q3

-0.576

B1

0.645

ENTE

3.290

HOMO

3.290

HOMO

3.290

HOMO

3.290

HOMO

3.290

HOMO

3.290

HOMO

3.290

HOMO

3.290

HOMO

3.290

HOMO

3.290

HOMO

3.290

HOMO

3.290

HOMO

3.290

EXIT

3.290

Q4

0.412

Q5

-1.028

Q6

0.688

B2

0.885

Q7

0.295

Q8

-0.496

Q9

0.481

DB3

-1.084

Q13

-0.522

Q14

0.528

Q15

-0.254

DCse

DCse

VF1

HF1

p

p+

m+

Surface Muon

μ+ (4MeV, 30MeV/c) from the decay of π+ stopped in the production target.

no surface μ- since the parent π- is promptly captured by nucleus.

TRANSPORT,TURTLE

5

Separation of positrons and muons by TOF

Positron Muon

200nsBeam Line 28.6m

Can be used to calibrate the muon momentum.

6

Surface Muon: momentum scan and yield

Drop by the window material

dE by the window

material ~ 1 MeV/c

Yield (Measurement)(by counting the Michel positrons ）1.5×107/s(for 1MW of proton)

Yield(MC)1.8×107/s(1MW)

Momentum Acceptance~6 ％ (FWHM)

The beamline acceptance is well understood.

7

G4Beamline Estimation

28 MeV/c μ-

G4Beamline model of D2 beam line

•Geometrical Acceptance:30 msr for point source

Detector for the Test Meas.

D2 Exit

Pb (4mmt) Plastic Scintillator

μ-

e-

B1B2 B3

• B1: gating-PMT readout

• B2: gating-PMT readout

• B3: ND filter (1/1000), normal PMT readout

•Have to detect delayed e- after prompt burst (>104/pulse).•Beam time approved is very short• → Use gating-PMT to increase delayed-time detection

efficiency.•Background e- coming from the decay of prompt μ- stopped in

counters.• → Pb plate to absorb μ- by muon capture process.• Electron-detection efficiency ~ 50%

gating PMT• No. of particles in a prompt

pulse~1e4

• Standard PMT is saturated.

• Used a gating PMT system

• off/on gain ratio = 1e6

Designed by Taniguchi

Snapshot of PMT signal

• B1• Plas. Scinti.• gating• B2• Plas. Scinti.• gating• B3• Plas. Scinti.• normal PMT• ND filtered

Baseline distortion due to delayed fluorescence from plastic scintillator.Individual hits by real particles can be seen on the baseline.

B1 pulse height(B2 tagged)

B2 pulse height(B1 tagged)

Time Spectrum

•e- from Bhabha scattering of e+ from μ+ decay.

•Ne+/Ne-@40-MeV/c = 450

•Dominate in Pe < 30 MeV/c

e-

e- from e+ scattering

MC simulated momentum spectra

e-

e- from e+ scattering

Mom. Spectrum

•pe > 40 MeV/c: Dominated by e- from μ- decay.

•pe ~ 50 MeV/c: Michel Edge

•pe < 30 MeV/c: Dominated by e- from e+ scattering where the e+ is coming from μ+ Michel decay.

•→ μ- stopping rate = 6 × 109 /sec/MW in the current fixed Target.

e-

e- from e+ scattering

π- production 2e13/MWFor 20-mm graphite= 0.9 mb

0.95 < θ < 1.150.10 GeV/c < p < 0.15 GeV/c

HARP: 0.4 mb

Geant4 (QGSP_BERT_HP)Good agreement with HARPEspecially p < 200 MeV/c region

Yield with the Rotation Target

167.5-mm outer r187.5-mm outer r