P41 (DeeMe)
Experimental Search
for µ-e Conversion in Nuclear Field
at Sensitivity of 10-14
with Pulsed Proton Beam from RCS
M. Aoki, Osaka University
on behalf of DeeMe Collabora9on
J-PARC PAC, 08/07/2011
11年7月8日金曜日
µ-e Conversion in Nuclear Field
• Muonic Atom (1S state)
Muon Capture(MC)
µ−
nuclei
Muon Decay in Orbit (DIO)
– MC:DIO = 1:1000(H), 2:1(Si), 13:1(Cu)
– τ(free μ-­‐) = 2.2 μs – τ(μ-­‐;Si) = 0.76 μs
• Charged Lepton Flavor Viola4on (CLFV)
μ-­‐e Conversion in Nuclear Field
Clear evidence of the new physics
2
11年7月8日金曜日
Rela9ons with other μ observables
• muon g-­‐2
– Δaμ: off by 3.3σ
• μ→e γ MEG 2009 analysis @ ICHEP2010(Paris)
– Most probable Nsig = 3.0 ~ 4.5、but sta4s4cally consistent with Nsig = 0
– B.R. = Nsig /1012
MEG talk at ICHEP2010 Paris
SINDRUM II Results
BR[μ-­‐ + Au → e-­‐ + Au] < 7 × 10-­‐13
BR[μ-­‐ + Ti → e-­‐ + Ti] < 4.3 × 10-­‐12
11年7月8日金曜日
G. Ishidori et al., PRD 75 (2007) 115019
Theore4cal Models
•
SUSY-GUT, SUSY-seesaw (Gauge Mediated process)
• BR = 10-14 = BR(μ→eγ) × O(α)
• τ→lγ
•
SUSY-seesaw (Higgs Mediated process)
• BR = 10-12~10-15
• τ→lη
N
N
B(μ→e conv) > 10-14
•
Doubly Charged Higgs Boson (LRS etc.)
• Logarithmic enhancement in a loop diagram for
μ-N → e-N, not for μ→e γ
•
•
M. Raidal and A. Santamaria, PLB 421 (1998) 250
and many others
11年7月8日金曜日
Andre de Gouvea
Principle of Measurement
• Process : μ-­‐ +(A,Z) → e-­‐ +(A,Z)
– A single mono-­‐energe4c electron
• 105 MeV
• Delayed：~1μS
SINDRUM II
• No accidental backgrounds
• Physics backgrounds
– Muon Decay in Orbit (DIO)
• Ee > 102.5 MeV (BR:10-­‐14)
• Ee > 103.5 MeV (BR:10-­‐16)
– Beam Pion Capture
• π-­‐+(A,Z) → (A,Z-­‐1)* → γ+(A,Z-­‐1)
γ → e+ e-­‐
• Prompt 4ming
SINDRUM II Results
BR[μ-­‐ + Au → e-­‐ + Au] < 7 × 10-­‐13
BR[μ-­‐ + Ti → e-­‐ + Ti] < 4.3 × 10-­‐12
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11年7月8日金曜日
DeeMe(P41)
• Process : μ-­‐ +(A,Z) → e-­‐ +(A,Z)
– A single mono-­‐energe4c electron
• 105 MeV
• Delayed：~1μS
• No accidental backgrounds
• Physics backgrounds
– Muon Decay in Orbit (DIO)
• Ee > 102.5 MeV (BR:10-­‐14)
• Ee > 103.5 MeV (BR:10-­‐16)
•Low Energy main part: suppressed by the – Beam Pion Capture
• π-­‐+(A,Z) → (A,Z-­‐1)* → γ+(A,Z-­‐1)
γ → e+ e-­‐
• Prompt 4ming
•Main pulse: Kicker to reduce the detector beamline.
•High Energy tail: Magnet Spectrometer (Δp < 0.3%)
rate.
•aeer-­‐protons: Suppressed owing to the extremely small aeer-­‐protons from RCS -­‐-­‐ RAP<10-­‐17.
6
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J-­‐PARC MLF Muon Facility
H-­‐line
o
rot
P
eV
3-­‐G
n
•1 MW : 3 GeV, 333 μA
•High sta9s9cs
•Fast-­‐Extracted Pulse Beam: 25 Hz 50 pulses
•Extremely small aeer-­‐protons
main pulses
600 ns
Proton Beam
Proton Target
600 ns
Primary Protons
40 ms
Time
D1 Instrument
11年7月8日金曜日
Surface muon or positive/negative muon slower than 50 MeV/c
Issues raised in the last PAC mee9ng
• Aeer-­‐Protons (a.k.a. Ex9nc9on)
– Plausible es9ma9on of the aeer protons,
– A clear plan for further studies to achieve the goal (if the goal was not achieved yet).
•
•
•
•
Method to es9mate the signal sensi9vity.
SiC target design; impacts on other experiments.
Encouragements to move forward with H-­‐line.
Background study, and In-­‐situ measurement of the backgrounds.
8
11年7月8日金曜日
Aeer-­‐Protons
• Preliminary Measurement was performed by K. Yamamoto at J-­‐PARC RCS group.
– NAP < ~10-­‐19
• Beam dynamics study is ongoing (in collabora9on with RCS group)
– (hardly) possible scenario of the aeer-­‐proton produc9on.
• A plan for further studies (in collabora9on with RCS group)
– developing into an in-­‐situ monitor system of the aeer-­‐
protons in physics runs.
9
11年7月8日金曜日
Preliminary
Measurement
•
aeer-­‐protons involve scaqered protons.
•
beam-­‐loss counters can observe it.
•
258 hours of mOFF
easurement
Kickers:
: ON
Esep1,2,3
by Kazami Yamamoto @ JAEA
Explore possible orbits
! -140 < x< -90 mm
! 10 < x < 30 mrad
KM1~3
QFL
! -140 < x< -92 mm
! 16 < x < 24 mrad
KM4~8
QDL
Might have
possibility
QFM
•
No evidence of the aeer-­‐protons so far. Measurement is limited by event sta9s9cs and the electrical noise from the RCS kickers. •
The above snapshot: RAP could be < ~10-­‐19
•
It is required to be < 10-­‐17
10
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Further Studies
• Pushing forward the measurement at RCS
– Large counter size
– Op9mize the counter loca9on(s)
• Downstream of the Septum.
• Downstream of the extrac9on kicker.
– to see the rate of protons failing in large-­‐emimance region.
• Downstream of a ring collimator sec9on.
– DAQ upgrade
• pulse-­‐by-­‐pulse recording,
• digital processing to separate the kicker noise and PMT signals.
• Beam dynamics simula9on + proton scaqering simula9on
– Precise es9ma9on of the counter efficiencies.
11
11年7月8日金曜日
Issues raised in the last PAC mee9ng
✓ Aeer-­‐Protons (a.k.a. Ex9nc9on)
✓ Plausible es9ma9on of the aeer protons,
✓ A clear plan for further studies to achieve the goal (if the goal is not achieved yet).
•
•
•
•
Method to es9mate the signal sensi9vity.
SiC target design; impacts on other experiments.
Encouragements to move forward with H-­‐line.
Background study, and In-­‐situ measurement of the backgrounds.
12
11年7月8日金曜日
•
•
•
•
Beamline: H-­‐line
the 1st concept by Jaap Doornbos (TRIUMF)
– mul9 purpose beamline
• DeeMe + g-­‐2 + muon-­‐HFS
– large acceptance
• > 110 msr
– straight sec9on for kickers and a separator.
– moderate Δp so that the BG’s can be monitored simultaneously.
Detailed design is ongoing (by MUSE/Naritoshi Kawamura)
MUSE/IMSS is pushing forward the construc9on down to muon-­‐HFS branch (short version).
P41(DeeMe) can run in the short-­‐version.
G4Beamline Model of
H-­‐line (short version)
13
11年7月8日金曜日
Issues raised in the last PAC mee9ng
✓ Aeer-­‐Protons (a.k.a. Ex9nc9on)
✓ Plausible es9ma9on of the aeer protons,
✓ A clear plan for further studies to achieve the goal (if the goal is not achieved yet).
• Method to es9mate the signal sensi9vity.
• SiC target design; impacts on other experiments.
✓ Encouragements to move forward with H-­‐line.
• Background study, and In-­‐situ measurement of the backgrounds.
14
11年7月8日金曜日
• Realis4c MC Study
• Signal Sensi4vity
– Nsig = 1.4 for BR=3×10-­‐14 (2×107sec)
Counts (/0.2MeV/c)
Sensi9vity and Backgrounds
• Backgrounds
–
102
DIO BG
10
μ-­‐e signal
1
-1
10
10-2
Assuming RAP=10-­‐19
Beam BG
10-3
10-4
90
95
100
105
110
115
120
Momentum (MeV/c)
or much less
Signal Region: 102.0 -­‐-­‐ 105.6 MeV/c
– Detector live-­‐4me Duty = only 1/20000
• If we could extend the run 4me up to 8×107 sec
– Nsig = 5.6, NBG=0.48 for the same cut: P[NBG>4]=0.0015
– Nsig = 4.8, NBG<0.02 for the 4ghter cut: P[NBG>2]=0.00008
P[Nsig>=2]=0.95
15
11年7月8日金曜日
Counts (/0.2MeV/c)
In-­‐situ Monitoring
of Backgrounds
1
10
10-2
0.25
10-3
10-4
0.2
90
95
100
From a Target ÷ 40
H-port Frange
GV Entrance
GV Exit
HS2 Entrance
HS3 Entrance
HSEP Entrance
HB4 Entrance
HB4 Exit
105
HQ2 Entrance
Focus
110
115
120
Momentum (MeV/c)
0.15
0.1
0.05
0
70
80
90
100
DIO BG
Signal
Acceptance (sr/MeV/c)
Background Monitoring
– Measure DIO electrons
• shape
• yield
– Prompt Backgrounds
• p>105.0 MeV/c (direct upper limit)
• Beam-­‐loss counters in RCS
– Cosmic-­‐induced Backgrounds
• Beam-­‐on: 50μsec/sec
• Beam-­‐off: >500msec/sec
10
-1
Moderate Δp of H-­‐line makes it possible to monitor backgrounds in situ.
– DIO backgrounds (p < 102.0 MeV/c)
– Prompt backgrounds (p > 105.6 MeV/c)
Signal Sensi9vity Calibra9on
– Measure number of DIO electrons.
– NDIO=300 (2e7 sec)
102
110
130
Prompt BG 120 (MeV/c)
Momentum
(Prompt BG)
Signal
Cosmic BG
16
11年7月8日金曜日
Detector Calibra9on
• Momentum Scale and Resolu9on
– place a calibra9on target in HB2
– prompt positron burst -­‐-­‐> g-­‐2 branch
– beam π+, μ+ stop in the target
-­‐-­‐> πe2, Michel positrons
• Acceptance Curve of H-­‐line
– exactly the same H-­‐line sezngs:
momentum@105 MeV/c, slits
– reduce the primary proton by 10-­‐8
• LINAC chopper: 10-­‐7
• Length of macro-­‐pulse: <10-­‐1
DeeMe Spectrometer
to g-­‐2 bran
ch
calibra9on target
17
11年7月8日金曜日
Issues raised in the last PAC mee9ng
✓ Aeer-­‐Protons (a.k.a. Ex9nc9on)
✓ Plausible es9ma9on of the aeer protons,
✓ A clear plan for further studies to achieve the goal (if the goal is not achieved yet).
✓ Method to es9mate the signal sensi9vity.
• SiC target design; impacts on other experiments.
✓ Encouragements to move forward with H-­‐line.
✓ Background study, and In-­‐situ measurement of the backgrounds.
18
11年7月8日金曜日
SiC Target R&D
• Impact to the other experiment
– Other exp. in MUSE: doubled yield of the surface muon -­‐> benefit to the other programs.
– neutron facility: primary proton loss 5%-­‐>10%
• It is allowed to have a 10% loss in the muon facility.
• neutron rate
– preliminary result from PHITS: doubled
– surface-­‐μ/n ra4o is the same.
• detailed study is ongoing:
– it will be con4nued awer Stage-­‐1.
• For the worst case: we can simply cut the thickness of SiC to half.
19
11年7月8日金曜日
Issues raised in the last PAC mee9ng
✓ Aeer-­‐Protons (a.k.a. Ex9nc9on)
✓ Plausible es9ma9on of the aeer protons,
✓ A clear plan for further studies to achieve the goal (if the goal is not achieved yet).
✓ Method to es9mate the signal sensi9vity.
✓ SiC target design; impacts on other experiments.
✓ Encouragements to move forward with H-­‐line.
✓ Background study, and In-­‐situ measurement of the backgrounds.
20
11年7月8日金曜日
Summary
•
•
•
•
•
•
•
•
•
There is a compe44ve merit of physics in searching for μ-­‐e conversion at sensi4vity of 10-­‐14 in 4mely manner.
It will maximize the poten4al of major discoveries at J-­‐PARC.
A preliminary measurement of the awer-­‐protons were performed. It seem to be much less than the original requirement. The installa4on of magnets in a H-­‐line tunnel is scheduled in the next summer.
A realis4c Monte Carlo study was performed. Major backgrounds are small enough.
The method to measure DIO, awer-­‐protons and cosmic-­‐induced backgrounds in situ was shown.
The method to do the detector calibra4on was shown.
DeeMe collabora4on does not see any technical difficul4es in the realiza4on of the proposed experiment.
The collabora4on is looking forward to receiving a Stage-­‐1 for the sake of:
– the nego4a4on with funding agency, and KAKENHI applica4on;
– the expansion of the collabora4on.
21
11年7月8日金曜日
End of Slides
11年7月8日金曜日