ミューオン崩壊で探る新物理 ~ MEG 実験...
Transcript of ミューオン崩壊で探る新物理 ~ MEG 実験...
九州大学 素粒子実験研究室セミナー, 22/Dec./2011
西口 創, KEK素核研
ミューオン崩壊で探る新物理 ~ MEG 実験 ~
Contents✤ Lepton Flavour Violation✤ μ→eγ Decay Search✤ MEG Experiment✤ Latest Results✤ Future Prospects
2
H.Nishiguchi (KEK) “ミューオン崩壊で探る新物理 - MEG -” 九州大学 素粒子実験研究室セミナー 22.Dec.2011
Lepton Flavour Violation
Particle’s Flavour Violation4
1 2 3
u
d
c
s
t
b
e
ν
μ
ν
τ
ν
mas
s sc
ale
generation
H.Nishiguchi (KEK) “ミューオン崩壊で探る新物理 - MEG -” 九州大学 素粒子実験研究室セミナー 22.Dec.2011
Particle’s Flavour Violation4
1 2 3
u
d
c
s
t
b
e
ν
μ
ν
τ
ν
mas
s sc
ale
generation
Quark Sector• Mixed by CKM mechanism• Experimentally Verified
➡ B factories
H.Nishiguchi (KEK) “ミューオン崩壊で探る新物理 - MEG -” 九州大学 素粒子実験研究室セミナー 22.Dec.2011
Particle’s Flavour Violation4
1 2 3
u
d
c
s
t
b
e
ν
μ
ν
τ
ν
mas
s sc
ale
generation
Quark Sector• Mixed by CKM mechanism• Experimentally Verified
➡ B factories
neutral Lepton Sector• Neutrino Oscillation • Experimentally Verified
➡ SK, SNO, KamLAND, etc.
H.Nishiguchi (KEK) “ミューオン崩壊で探る新物理 - MEG -” 九州大学 素粒子実験研究室セミナー 22.Dec.2011
Particle’s Flavour Violation4
1 2 3
u
d
c
s
t
b
e
ν
μ
ν
τ
ν
mas
s sc
ale
generation
Quark Sector• Mixed by CKM mechanism• Experimentally Verified
➡ B factories
neutral Lepton Sector• Neutrino Oscillation • Experimentally Verified
➡ SK, SNO, KamLAND, etc.
charged Lepton Sector• source from beyond SM ??• never observed yet !!?
?
H.Nishiguchi (KEK) “ミューオン崩壊で探る新物理 - MEG -” 九州大学 素粒子実験研究室セミナー 22.Dec.2011
Why charge LFV has never been observed ?5
SM + simple ν Oscillation• charged LFV is possible
• but extremely rare (small ν)
• B(μ→eγ) = 10-50 ~10 -40 !!!
μ e
w
ν oscill.
γe.g.
H.Nishiguchi (KEK) “ミューオン崩壊で探る新物理 - MEG -” 九州大学 素粒子実験研究室セミナー 22.Dec.2011
Why charge LFV has never been observed ?5
SM + simple ν Oscillation• charged LFV is possible
• but extremely rare (small ν)
• B(μ→eγ) = 10-50 ~10 -40 !!!
μ e
w
ν oscill.
γe.g.
beyond SM (SUSY-GUT etc.)
• charged LFV is largely enhanced
• still rare but observable level
• B(μ→eγ) = 10-15 ~10 -11 !!!
μ e
γ
χ0μ e
e.g.
H.Nishiguchi (KEK) “ミューオン崩壊で探る新物理 - MEG -” 九州大学 素粒子実験研究室セミナー 22.Dec.2011
Why charged LFV is Attractive ?6
Only charged LFV has never been observed
Neutrino Oscillation is possible by “SM + ν mass”
Quark Mixing is generally contaminated by SM
➡ charged LFV is “NEW PHYSICS”
Experimental Upper Limit is already sensitive to predicted region
e.g. μ→eγ is the most sensitive mode to search for charged LFV
Muon can be generated most easily. → Suitable for rare decay search experiment.
H.Nishiguchi (KEK) “ミューオン崩壊で探る新物理 - MEG -” 九州大学 素粒子実験研究室セミナー 22.Dec.2011
Scenarios -1-7
✤ Supersymmetric Standard Model; The most well motivated model✤ Induced by slepton mixing
(1)Supersymmetric Standard Model
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(1)Supersymmetric Standard Model
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?@&,#(6#'+/(,56&-A✤ Supersymmetric Models with See-Saw Mechanism✤ Large slepton mixing is induced through renormalization
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- Hisano, Moroi, Tobe, Yamaguchi (1996)- Barbieri, Hall (1994)
- Hisano, Nomura (1999)- Borzumati, Masiero (1986)
H.Nishiguchi (KEK) “ミューオン崩壊で探る新物理 - MEG -” 九州大学 素粒子実験研究室セミナー 22.Dec.2011
Scenarios -2-8
✤ Little Higgs Model with T-Parity
✤ Exchange of the T-odd gauge bosons and the T-odd fermions
✤ Misalignment of physical base against flavour base
(2)Little Higgs Model with T Parity
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- Blanke, Buras, Duling, Poschenrieder, Tarantino
✤ Extra dimensional models✤ Anarchic RS model
✤ Fermions are located in different plane in 5D to explain Yukawa’s Non-universal coupling to KK gauge bosons even in flavour base
(2) Extra dimensional models
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- Agashe, Blechman, PetrielloH.Nishiguchi (KEK) “ミューオン崩壊で探る新物理 - MEG -” 九州大学 素粒子実験研究室セミナー 22.Dec.2011
Which is the best probe ?9
78 W. Altmannshofer et al. / Nuclear Physics B 830 (2010) 17–94
Table 8“DNA” of flavour physics effects for the most interesting observables in a selection of SUSY and non-SUSY models
signals large effects, visible but small effects and implies that the given model does not predictsizable effects in that observable.
AC RVV2 AKM !LL FBMSSM LHT RS
D0 ! D0 ?
"K
S#$
S$KS?
ACP(B " Xs% ) ?
A7,8(B " K#µ+µ!) ?
A9(B " K#µ+µ!) ?
B " K(#)&&
Bs " µ+µ!
K+ " '+&&
KL " '0&&
µ " e%
( " µ%
µ + N " e + N
dn
de
(g ! 2)µ ?
RVV2, AKM) and (LHT, RS) models can easily be made with the help of BR(Bs " µ+µ!) andBR(K+ " '+&&) only but the inclusion in this test of S#$ will be very helpful. The distinctionbetween the AC and RVV2 models has been discussed in the previous sections while the onebetween LHT and RS in [16,77]. Here the correlation between KL " '0&& and K+ " '+&&
markedly different in both models and the hierarchy in (7.1) could play important roles.
7.2. DNA-flavour test of new physics models
We have seen in the previous sections and in Section 7.1 that the patterns of flavour violationfound in various extensions of the SM differed from model to model, thereby allowing in thefuture to find out which of the models considered by us, if any, can survive the future measure-ments. Undoubtedly, the correlations between various observables that are often characteristicfor a given model will be of the utmost importance in these tests.
In Table 8, we show a summary of the potential size of deviations from the SM results allowedfor a large number of observables considered in the text, when all existing constraints from otherobservables not listed there are taken into account. We distinguish among:
✤ Anatomy and phenomenology of FCNC and CPV effects in SUSY theories
Nucl. Phys. B830 (2010) pp. 17-94
H.Nishiguchi (KEK) “ミューオン崩壊で探る新物理 - MEG -” 九州大学 素粒子実験研究室セミナー 22.Dec.2011
Which is the best probe ?9
78 W. Altmannshofer et al. / Nuclear Physics B 830 (2010) 17–94
Table 8“DNA” of flavour physics effects for the most interesting observables in a selection of SUSY and non-SUSY models
signals large effects, visible but small effects and implies that the given model does not predictsizable effects in that observable.
AC RVV2 AKM !LL FBMSSM LHT RS
D0 ! D0 ?
"K
S#$
S$KS?
ACP(B " Xs% ) ?
A7,8(B " K#µ+µ!) ?
A9(B " K#µ+µ!) ?
B " K(#)&&
Bs " µ+µ!
K+ " '+&&
KL " '0&&
µ " e%
( " µ%
µ + N " e + N
dn
de
(g ! 2)µ ?
RVV2, AKM) and (LHT, RS) models can easily be made with the help of BR(Bs " µ+µ!) andBR(K+ " '+&&) only but the inclusion in this test of S#$ will be very helpful. The distinctionbetween the AC and RVV2 models has been discussed in the previous sections while the onebetween LHT and RS in [16,77]. Here the correlation between KL " '0&& and K+ " '+&&
markedly different in both models and the hierarchy in (7.1) could play important roles.
7.2. DNA-flavour test of new physics models
We have seen in the previous sections and in Section 7.1 that the patterns of flavour violationfound in various extensions of the SM differed from model to model, thereby allowing in thefuture to find out which of the models considered by us, if any, can survive the future measure-ments. Undoubtedly, the correlations between various observables that are often characteristicfor a given model will be of the utmost importance in these tests.
In Table 8, we show a summary of the potential size of deviations from the SM results allowedfor a large number of observables considered in the text, when all existing constraints from otherobservables not listed there are taken into account. We distinguish among:
✤ Anatomy and phenomenology of FCNC and CPV effects in SUSY theories
Nucl. Phys. B830 (2010) pp. 17-94
All models are sensitive to these 2 processes !!
H.Nishiguchi (KEK) “ミューオン崩壊で探る新物理 - MEG -” 九州大学 素粒子実験研究室セミナー 22.Dec.2011
μ→eγ Decay Searchand
MEG Experiment
Two Major Muon LFV Processes11
e-N
μ -
e+
μ +
γ
μ→eγ μN→eN
H.Nishiguchi (KEK) “ミューオン崩壊で探る新物理 - MEG -” 九州大学 素粒子実験研究室セミナー 22.Dec.2011
History of μ→eγ Search Experiment12
✤ Long Tradition on the μ→eγ Search Experiment
✤ Started right after the muon discovery
✤ μ→eγ has already entered the predicted region !!
✤ NOW VERY VERY ATTRACTIVE !!!!!
Upp
er L
imit
on B
ranc
hing
Rat
io
10-15
10-13
10-11
10-9
10-7
10-5
10-3
10-1
1950 1970 1990 2010
H.Nishiguchi (KEK) “ミューオン崩壊で探る新物理 - MEG -” 九州大学 素粒子実験研究室セミナー 22.Dec.2011
Past μ→eγ Experiments
Previous Upper Limit (1999)
Best Limit on μ→eγ BR (2011)
Expected Reach on μ→eγ BR
History of μ→eγ Search Experiment12
✤ Long Tradition on the μ→eγ Search Experiment
✤ Started right after the muon discovery
✤ μ→eγ has already entered the predicted region !!
✤ NOW VERY VERY ATTRACTIVE !!!!!
Upp
er L
imit
on B
ranc
hing
Rat
io
10-15
10-13
10-11
10-9
10-7
10-5
10-3
10-1
1950 1970 1990 2010
H.Nishiguchi (KEK) “ミューオン崩壊で探る新物理 - MEG -” 九州大学 素粒子実験研究室セミナー 22.Dec.2011
Predicted Region for μ→eγ
Past μ→eγ Experiments
Previous Upper Limit (1999)
Best Limit on μ→eγ BR (2011)
Expected Reach on μ→eγ BR
Hunting for μ→eγ ✤ Signal and Backgrounds
✤ Clear 2-body kinematics (Ee=Eγ=52.8MeV, θeγ=180°, Time Coincidence)
✤ Sensitivity is Limited by “Accidental Overlap”
✤ DC muon is the Best Solution
✤ Good Resolution (Energy, Spacial and Timing) under Very High Rate
13
Sign
al
Prom
pt B
G.
Accid
enta
l BG.
H.Nishiguchi (KEK) “ミューオン崩壊で探る新物理 - MEG -” 九州大学 素粒子実験研究室セミナー 22.Dec.2011
Features of MEG14
✤ Sensitivity is Limited by “Accidental Overlap”
✤ DC muon is the Best Solution
✤ Good Resolution (Energy, Spacial and Timing) under Very High Rate
World Most Intense DC Muon Beam at PSI
108 muon/sec
Liquid Xenon Scintillation Detector
(gamma)
COBRA Spectrometer(positron)
H.Nishiguchi (KEK) “ミューオン崩壊で探る新物理 - MEG -” 九州大学 素粒子実験研究室セミナー 22.Dec.2011
PSI and its Cyclotron Facility15
H.Nishiguchi (KEK) “ミューオン崩壊で探る新物理 - MEG -” 九州大学 素粒子実験研究室セミナー 22.Dec.2011
PSI and its Cyclotron Facility15
H.Nishiguchi (KEK) “ミューオン崩壊で探る新物理 - MEG -” 九州大学 素粒子実験研究室セミナー 22.Dec.2011
PSI and its Cyclotron Facility15
H.Nishiguchi (KEK) “ミューオン崩壊で探る新物理 - MEG -” 九州大学 素粒子実験研究室セミナー 22.Dec.2011
MEG Detector Apparatus16
(1) World’s Most Intense DC Muon Beam
(2) Specially Graded Solenoidal Magnet
(3) Very LIGHT and Sensitive DC, and Very Fast TC
(4) Liquid Xenon Scintillation Photon Detector
The MEG Collaboration( 5 countries ,/12 institutes / ~60 persons )
H.Nishiguchi (KEK) “ミューオン崩壊で探る新物理 - MEG -” 九州大学 素粒子実験研究室セミナー 22.Dec.2011
Liquid Xenon Scintillation γ Detector17
✤ Homogeneous Volume ( ~800l ) is surrounded by PMTs on all faces
✤ 846 PMTs submerged in the liquid✤ Energy Measurement
✤ All PMT outputs✤ σE/E ~ 2% (@52.8MeV)
✤ Position Measurement✤ PMTs on the inner face✤ σx = 5-6 mm (@52.8MeV)
✤ Timing Measurement✤ Averaging of signal arrival time
of selected PMTs✤ σt ~ 70 ps (@52.8MeV)
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.3
Liquid Xenon Detector! 900 liter liquid xenon ! 846 2” PMTs (Hamamatsu R9869)
" immersed in LXe directly
! Good uniformity ( homogeneous, liquid )! High light output ( ~75% of NaI )! Short decay time ( 45ns )! High density (3g/cm3)
! Short scintillation wavelength ~ 175nm" Quartz window for PMT
! Low temperature 165K" pulse tube cryocooler developed by KEK
! Purification to remove H2O, O
2, N
2 etc.
.C+#D/CE$DFG HI$JKLMNOPQRSTU E VW
H.Nishiguchi (KEK) “ミューオン崩壊で探る新物理 - MEG -” 九州大学 素粒子実験研究室セミナー 22.Dec.2011
COBRA Positron Spectrometer18
Solenoid
superconducting solenoid gradient B-field (0.5-1.7 T) very thin conductor and cryostat wall (0.2X0)
Drift Chamber
segmented radially (16 sectors) helium:ethane (50:50) opened-frame very thin cathode foil with pads
Timing Counter
2-layers of scintillators - scintillator bars (outer) - scintillator fibres (inner)
H.Nishiguchi (KEK) “ミューオン崩壊で探る新物理 - MEG -” 九州大学 素粒子実験研究室セミナー 22.Dec.2011
MEG History19
2007
2008
2009
2010
2011
JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC
Detector Construction / InstallationBeam Line Commissioning
Engineering / Pilot Run
Detector Maintenance / Minor Upgrades
Beam Line Commissioning
Conditioning / Calibration Runs1st Physics Run
Detector Maintenance / Minor UpgradesConditioning / Calibration Runs
2nd Physics Run1st Result(Prelimnl.)
Detector Maintenance / Repairs / Minor UpgradesCalibrations 3rd Physics Run
Calib. Repairs
4th Physics RunDetector Maintenance
2nd+3rd Result
2nd Result(Prelimnl.)
1st Result(Final)
H.Nishiguchi (KEK) “ミューオン崩壊で探る新物理 - MEG -” 九州大学 素粒子実験研究室セミナー 22.Dec.2011
MEG Run2008 (1st Physics Run)20
✤ Severe Problem on DC discharge✤ e+ efficiency/resolution
✤ Crisis...✤ Trigger efficiency
✤ Only ~14%...
✤ 12/Sep.-16/Dec. MEG Physics ✤ 8.4×1013 muon stops✤ but very poor efficiency...
✤ Final Result (2008) ;✤ B(μ→eγ) < 2.8×10-11 (90CL.)
✤ (sensitivity : 1.3×10-11 )✤ Nucl.Phys. B 834 (2010) 1-12
H.Nishiguchi (KEK) “ミューオン崩壊で探る新物理 - MEG -” 九州大学 素粒子実験研究室セミナー 22.Dec.2011
2008 2009
γ Energy σEγ (%) 2.0 (depth>2cm) 1.9γ Timing σtγ (ps) 80 96γ Position σxγ (mm) 5/6 ←
γ Efficiency εγ (%) 63 58e+ Mom. σpe (%) 1.6 (80%core) 0.59
e+ Timing σte (ps) <125 107e+ Angle σθe (mrad) 10(φ)/18(θ) 6.7(φ)/9.4(θ)e+ Efficiency εe (%) 14 40γ-e+ Relative Timing 148 146μ+ decay vertex (mm) 3.2/4.5 1.5/1.1Trigger Efficiency (%) 66 91μ+ Stopping Rate (Hz) 3×107 2.9×107
DAQ Time (days) 48 (78) 35 (43)Sensitivity 1.3×10-11 0.92×10-12
BR Upper Limit 2.8×10-11 coming soon
21
✤ Several Big Improvements✤ e+ efficiency/resolution
✤ Thanks to solving discharge problem
✤ Trigger efficiency
✤ DAQ time is shorter than 2008 due to other experiment sharing area
✤ Statistics-2009 : ~2×2008
✤ Compensated by efficiency improvements
MEG Run2009 (2nd Physics Run)
H.Nishiguchi (KEK) “ミューオン崩壊で探る新物理 - MEG -” 九州大学 素粒子実験研究室セミナー 22.Dec.2011
2008 2009 2010
γ Energy σEγ (%) 2.0 (depth>2cm) 1.9 ←
γ Timing σtγ (ps) 80 96 67γ Position σxγ (mm) 5/6 ← ←
γ Efficiency εγ (%) 63 58 59e+ Mom. σpe (%) 1.6 (80%core) 0.59 0.62
e+ Timing σte (ps) <125 107 ←
e+ Angle σθe (mrad) 10(φ)/18(θ) 6.7(φ)/9.4(θ) 7.2(φ)/11(θ)e+ Efficiency εe (%) 14 40 34γ-e+ Relative Timing 148 146 122μ+ decay vertex (mm) 3.2/4.5 1.5/1.1 2.0/1.1Trigger Efficiency (%) 66 91 92μ+ Stopping Rate (Hz) 3×107 2.9×107 ←
DAQ Time (days) 48 (78) 35 (43) 56 (67)Sensitivity 1.3×10-11 0.92×10-12 0.44×10-12
BR Upper Limit 2.8×10-11 coming soon coming soon
22
✤ Better Electronics Timing Accuracy by new digitizer (DRS4)
✤ Shorter Beamtime than planned
✤ Statistics : ~1.9×2009
MEG Run2010 (3rd Physics Run)
H.Nishiguchi (KEK) “ミューオン崩壊で探る新物理 - MEG -” 九州大学 素粒子実験研究室セミナー 22.Dec.2011
Analysis Procedure23
✤ Blind Analysis✤ Signal region was hidden until
analysis fixed ✤ Any study (calibration, BG
estimation, performance evaluation) can be done with events outside the box
✤ Hidden parameters (Eγ, Teγ)✤ Sideband Data
✤ Accidental BG can be studied with off-timing sideband data
✤ Radiative decay can be studied with low energy sideband data
✤ Normalization✤ Unbiased Michel data mixed in
physics data✤ Wide Analysis Region
✤ for likelihood fittingH.Nishiguchi (KEK) “ミューオン崩壊で探る新物理 - MEG -” 九州大学 素粒子実験研究室セミナー 22.Dec.2011
Analysis Procedure23
✤ Blind Analysis✤ Signal region was hidden until
analysis fixed ✤ Any study (calibration, BG
estimation, performance evaluation) can be done with events outside the box
✤ Hidden parameters (Eγ, Teγ)✤ Sideband Data
✤ Accidental BG can be studied with off-timing sideband data
✤ Radiative decay can be studied with low energy sideband data
✤ Normalization✤ Unbiased Michel data mixed in
physics data✤ Wide Analysis Region
✤ for likelihood fitting
Blind
H.Nishiguchi (KEK) “ミューオン崩壊で探る新物理 - MEG -” 九州大学 素粒子実験研究室セミナー 22.Dec.2011
Analysis Procedure23
✤ Blind Analysis✤ Signal region was hidden until
analysis fixed ✤ Any study (calibration, BG
estimation, performance evaluation) can be done with events outside the box
✤ Hidden parameters (Eγ, Teγ)✤ Sideband Data
✤ Accidental BG can be studied with off-timing sideband data
✤ Radiative decay can be studied with low energy sideband data
✤ Normalization✤ Unbiased Michel data mixed in
physics data✤ Wide Analysis Region
✤ for likelihood fitting
BlindLeft Sideband
Right Sideband
H.Nishiguchi (KEK) “ミューオン崩壊で探る新物理 - MEG -” 九州大学 素粒子実験研究室セミナー 22.Dec.2011
Analysis Procedure23
✤ Blind Analysis✤ Signal region was hidden until
analysis fixed ✤ Any study (calibration, BG
estimation, performance evaluation) can be done with events outside the box
✤ Hidden parameters (Eγ, Teγ)✤ Sideband Data
✤ Accidental BG can be studied with off-timing sideband data
✤ Radiative decay can be studied with low energy sideband data
✤ Normalization✤ Unbiased Michel data mixed in
physics data✤ Wide Analysis Region
✤ for likelihood fitting
BlindLeft Sideband
Right Sideband
Eγ Sideband
H.Nishiguchi (KEK) “ミューオン崩壊で探る新物理 - MEG -” 九州大学 素粒子実験研究室セミナー 22.Dec.2011
Likelihood Analysis24
✤ Fit Parameters : # of events Nsig, NRD and NBG (N=Nsig+NRD+NBG)✤ Observables : Energy Eγ, Ee, Relative time Teγ and Opening angle θeγ, φeγ
✤ Probability Density Function for each event type (S, R, B)✤ PDFs are extracted from data
✤ Fit in Wide region (10σ)✤ Fit Signal and Background simultaneously
✤ Three Independent Analysis Tools
✤ Extended unbinned maximum likelihood analysis on number of events
Different PDF implementation Fit or Input NRDDifferent Statistical treatment
(Frequentist or Bayesian)
check, understandingor find bug
L(Nsig, NRD, NBG)
=NNobse−N
Nobs
Nobs�
i=i
�Nsig
NS +
NRD
NR +
NBG
NB
�
H.Nishiguchi (KEK) “ミューオン崩壊で探る新物理 - MEG -” 九州大学 素粒子実験研究室セミナー 22.Dec.2011
PDFs - Energies, Angles and Timing -25
a.u.
Ee Signal PDF(from measured
resolution)
Ee BG PDF(from L/R sideband)
Eγ Signal PDF(from 55MeV γ)(using π0 beam)
Eγ BG PDF(from L/R sideband)
Teγ Signal PDF(from RD peak)
Relative Angle (θeγ, φeγ) PDF
Signal : from measured resolution
Background : from L/R sideband
H.Nishiguchi (KEK) “ミューオン崩壊で探る新物理 - MEG -” 九州大学 素粒子実験研究室セミナー 22.Dec.2011
Normalization - # of Muon Decay -26
✤ # of Michel Positrons is counted simultaneously using highly pre-scaled trigger applying the same event selection as for the physics data sample.
✤ Advantage: Independent of beam-rate & in 1st-order insensitive to acceptances & efficiencies (ratios)
✤ Branching ratio is represented by obtained normalization factor “k” and the # of signal which will be obtained by the final analysis
B(µ+ → e+γ)B(µ+ → e+νν)
=Nsig
Neνν× f e
eνν
P · �pu× �trigeνν
�trigeγ
× �DCeνν
�DCeγ
× 1Ageo
eγ× 1
�eγ
B(µ+ → e+γ) =k
Nsig
H.Nishiguchi (KEK) “ミューオン崩壊で探る新物理 - MEG -” 九州大学 素粒子実験研究室セミナー 22.Dec.2011
Experimental Sensitivity27
✤ Mean Upper Limit (90%C.L.) on ensemble of toy-MC experiments✤ Generate events with obtained PDFs assuming Null-Result Hypothesis ✤ Repeat toy-MC experiments and calculate Upper Limit for each
experiment in the same way as real data
✤ Signal-detection power of our likelihood analysis was also checked by dedicated toy-MC with mixed μ→eγ signal events
H.Nishiguchi (KEK) “ミューオン崩壊で探る新物理 - MEG -” 九州大学 素粒子実験研究室セミナー 22.Dec.2011
# of μ+ S.E.S. Expected Obtained
2008 9.5×1013 1.3×10-11 1.3×10-11 2.8×10-11
2009 6.0×1013 0.92×10-12 3.3×10-12
2010 1.2×1014 0.44×10-12 2.2×10-12
Sideband Fits28
✤ To confirm the final analysis, Off-timing Sideband data is fitted
Left Sideband
Right SidebandBlind
H.Nishiguchi (KEK) “ミューオン崩壊で探る新物理 - MEG -” 九州大学 素粒子実験研究室セミナー 22.Dec.2011
Finally.....29
✤ Signal Box is Blinded✤ Likelihood is Constructed✤ PDF is Built✤ Resolutions/Efficiencies are Evaluated✤ Background is Estimated✤ Normalization is Done✤ Experimental Sensitivity is Estimated✤ Everything is Confirmed in Sideband Fit
and thus...H.Nishiguchi (KEK) “ミューオン崩壊で探る新物理 - MEG -” 九州大学 素粒子実験研究室セミナー 22.Dec.2011
Finally.....30
Now Ready to Open the BOX !!
H.Nishiguchi (KEK) “ミューオン崩壊で探る新物理 - MEG -” 九州大学 素粒子実験研究室セミナー 22.Dec.2011
Calorimeter sum WF
Spectrometer hits and a track
MEG Latest Results(Physics Data of 2009 and 2010)
2009 Unblinded Event Distribution32
H.Nishiguchi (KEK) “ミューオン崩壊で探る新物理 - MEG -” 九州大学 素粒子実験研究室セミナー 22.Dec.2011
2009 Event Distributions
ecos-1 -0.9995 -0.999 -0.9985 -0.998
(nse
c)et
-2
-1.5
-1
-0.5
0
0.5
1
1.5
2
21
3
76
9
(MeV)eE50 51 52 53 54 55 56
(MeV
)E
48
49
5051
52
53
54
5556
5758
2137
4
2009 data update
Nsig = 3.0 Nsig = 3.4
!"#"$%&'()!"#$!%&'()*+,-../#$0..1)*'23.4#5 61%7$%66.8#9-..6('23%7#%66.8#9
UL @90% C.L. = 9.6×10-12
2009 Event Distributions
ecos-1 -0.9995 -0.999 -0.9985 -0.998
(nse
c)et
-2
-1.5
-1
-0.5
0
0.5
1
1.5
2
21
3
76
9
(MeV)eE50 51 52 53 54 55 56
(MeV
)E
48
49
5051
52
53
54
5556
5758
2137
4
2009 data update
Nsig = 3.0 Nsig = 3.4
!"#"$%&'()!"#$!%&'()*+,-../#$0..1)*'23.4#5 61%7$%66.8#9-..6('23%7#%66.8#9
UL @90% C.L. = 9.6×10-12
Sample Event Display33
✤ Highest Ranked (=most signal-like) Event✤ No pileup, Relative Angle and Relative Timing are checked.✤ Every highly ranked events are checked carefully.
!"#$%&&'()*$#&+'&%,&-$../.01$23.31$456786$9)7'('6'&$:;$<&=8):>:*5$$$$$<:78(56?($9@A%:':$..B#&+'&%,&-B23.3
2C
Event display
Each highly ranked event is checked carefully.
Calorimeter sum WF Calorimeter PMT hit map
Spectrometer hits and a track
PMT sum WF
calorimeter PMT hit map
spectrometer hit & track
H.Nishiguchi (KEK) “ミューオン崩壊で探る新物理 - MEG -” 九州大学 素粒子実験研究室セミナー 22.Dec.2011
2009 Likelihood Fit / CL Curve34
H.Nishiguchi (KEK) “ミューオン崩壊で探る新物理 - MEG -” 九州大学 素粒子実験研究室セミナー 22.Dec.2011
BR < 9.6×10-12
(90CL.)
Teγ Ee Eγ
θeγ φeγ
totalacc.rad.sig.
2010 Unblinded Event Distribution35
H.Nishiguchi (KEK) “ミューオン崩壊で探る新物理 - MEG -” 九州大学 素粒子実験研究室セミナー 22.Dec.2011
ecos-1 -0.9995 -0.999 -0.9985 -0.998
(nse
c)et
-2
-1.5
-1
-0.5
0
0.5
1
1.5
2
1
(MeV)eE50 51 52 53 54 55 56
(MeV
)E
48
49
5051
52
53
54
5556
5758
2
2010 data unblinded on July 5th
!"#$!%&'()*+,--./+0#$%-1&'2223 45%6$%44-7#8,--4('9%6#%44-7#8
ecos-1 -0.9995 -0.999 -0.9985 -0.998
(nse
c)et
-2
-1.5
-1
-0.5
0
0.5
1
1.5
2
1
(MeV)eE50 51 52 53 54 55 56
(MeV
)E
48
49
5051
52
53
54
5556
5758
2
2010 data unblinded on July 5th
!"#$!%&'()*+,--./+0#$%-1&'2223 45%6$%44-7#8,--4('9%6#%44-7#8
2010 Likelihood Fit / CL Curve36
H.Nishiguchi (KEK) “ミューオン崩壊で探る新物理 - MEG -” 九州大学 素粒子実験研究室セミナー 22.Dec.2011
BR < 1.7×10-12
(90CL.)
Teγ Ee Eγ
θeγ φeγ
totalacc.rad.sig.
2009-2010 Combined37
H.Nishiguchi (KEK) “ミューオン崩壊で探る新物理 - MEG -” 九州大学 素粒子実験研究室セミナー 22.Dec.2011
2009 2010
BR(fit) LL(90CL)
UL(90CL)
2009 3.2×10-12 1.7×10-12 9.6×10-12
2010 -9.9×10-13 -- 1.7×10-12
2009+2010 -1.5×10-13 -- 2.4×10-12
MEG 2009-2010 Conclusion38
H.Nishiguchi (KEK) “ミューオン崩壊で探る新物理 - MEG -” 九州大学 素粒子実験研究室セミナー 22.Dec.2011
✤ MEG(2009+2010) is still consistent with Null Result
✤ BR(μ→eγ) < 2.4×10-12 (90%CL.)
✤ Best Upper Limit on BR(μ→eγ) is Updated for the 1st time in 12 years.
✤ Factor 5 restricted result !!
MEG Latest Result39
H.Nishiguchi (KEK) “ミューオン崩壊で探る新物理 - MEG -” 九州大学 素粒子実験研究室セミナー 22.Dec.2011
Future Topics
MEG 2011 (4th Physics Run)
✤ Finished on December/02.
✤ The 1st long term experiment, longer than 5 months
✤ approx. same statistics as “2009+2010”
✤ Analysis (Calibration / Performance Estimation / BG Estimation) is ongoing.
✤ Result will be presented in Summer 2012, as usual, hopefully.
41
H.Nishiguchi (KEK) “ミューオン崩壊で探る新物理 - MEG -” 九州大学 素粒子実験研究室セミナー 22.Dec.2011
MEG Prospect (within the 1st phase, ~2015)42
2008
2009
2010 2011 2012
data UL (2009+2010)
data UL (2009)
✤ RUN2009+2010 is present best limit
✤ RUN2011 will enter the O(~13) world
✤ Until RUN2012 will be same condition(+minor UG)
✤ After RUN2013, several UG is planned
✤ eg. cable replacement in order to improve the position efficiency
✤ (nb. nothing is decided yet...)
H.Nishiguchi (KEK) “ミューオン崩壊で探る新物理 - MEG -” 九州大学 素粒子実験研究室セミナー 22.Dec.2011
MEG-2 (Improved MEG)43
✤ Bacc ∝ δEe × δteγ × (δEγ)2 × (δθeγ)2 ✤ 10 Times Better Sensitivity could be expected.
Detector Modifiable Item Possible Improvement
LXe CalorimeterHigh QE PMT δEγ×0.65 / δteγ×0.77
LXe CalorimeterFiner Granularity δθeγ×0.72 / Bacc×0.6
Drift Chamber Reduce Material δEe×0.8 / εe×1.25
General Double Acceptance Bacc×0.5
H.Nishiguchi (KEK) “ミューオン崩壊で探る新物理 - MEG -” 九州大学 素粒子実験研究室セミナー 22.Dec.2011
MEG-3 (Polarized MEG)44
✤ By the use of a polarized muon beam and a Suitable target, a polarized MEG can be performed.
✤ Based on a sufficient # of observed μ→eγ events, the positron angular distribution with respect to the muon spin orientation can be extracted and used to discriminate between different SUSY-GUT models.
the asymmetry of the e+ angular disribution
measuring the e+ emission angle distribution
polarized beam + depolarization target + MEG
MC study was performed to estimate feasibility
Possible to distinguish A = -1, 0, +1 at 68% C.L. for Br(µ+→e+γ) > 10-12.5 by a polarized MEG
A = +1A = -1
A = 0
H.Nishiguchi (KEK) “ミューオン崩壊で探る新物理 - MEG -” 九州大学 素粒子実験研究室セミナー 22.Dec.2011
Summary✤ Charged LFV is very attractive to explore the new physics beyond Standard Model.
✤ μ→eγ decay is the most sensitive to such a charged lepton flavour violation.✤ After longer than 60 years history, B(μ→eγ) achieved <1.2×10-11 (previous limit)
✤ MEG experiment started 2008 and is currently running in order to discover the first event of charged lepton flavour violation, in other words, evidence of new physics.✤ Run2008(1st) : B(μ→eγ) < 2.8×10-11 (very poor efficiency/resolution)✤ Run2009(2nd)
✤ 2×Run2008 Statistics (full efficiency)✤ Run2010(3rd)
✤ 1.9×Run2009 Statistics ✤ Combined Result : B(μ→eγ) < 2.4×10-12 (90CL.) (BEST LIMIT)✤ 5 times more restricted limit to the new physics
✤ Run2011(4th)✤ same statistics as “Run2009 + Run2010”✤ Analysis is ongoing
✤ MEG will achieve O(10-13) SOON and give us an important information, interesting and complemental with LHC.
45
H.Nishiguchi (KEK) “ミューオン崩壊で探る新物理 - MEG -” 九州大学 素粒子実験研究室セミナー 22.Dec.2011