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