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Status of the MEG Experiment Status of the MEG Experiment
W. OotaniW. OotaniICEPP, University of TokyoICEPP, University of Tokyo
for the MEG collaborationfor the MEG collaboration
Wataru Ootani, Wataru Ootani, ICEPP, University of TokyoICEPP, University of Tokyo NP02, Kyoto, Sep. 27-29 2002NP02, Kyoto, Sep. 27-29 2002
OutlineOutline
• Physics motivations for Physics motivations for the MEG experimentthe MEG experiment• MEG detectorMEG detector• Status of the sub-detectorsStatus of the sub-detectors
Beam lineBeam line Photon detectorPhoton detector Positron spectrometerPositron spectrometer
• MagnetMagnet• Drift chamberDrift chamber• Timing counterTiming counter
Trigger, DAQ, and slow controlTrigger, DAQ, and slow control• SummarySummary
Wataru Ootani, Wataru Ootani, ICEPP, University of TokyoICEPP, University of Tokyo NP02, Kyoto, Sep. 27-29 2002NP02, Kyoto, Sep. 27-29 2002
MEGMEG Collaboration Collaboration
A. BaldiniA. Baldini44, A. de Bari, A. de Bari55, L. M. Barkov, L. M. Barkov11, C. Bemporad, C. Bemporad44, P.Cattaneo, P.Cattaneo55, , G. CecchetG. Cecchet55, F. Cei, F. Cei44, T. Doke, T. Doke88, J. Egger, J. Egger66, M.Grassi, M.Grassi44, A. A. Grebenuk, A. A. Grebenuk11, ,
T. HaruyamaT. Haruyama44, P. -R. Kettle, P. -R. Kettle66, B. Khazin, B. Khazin11, J. Kikuchi, J. Kikuchi88, Y. Kuno, Y. Kuno33, A. Maki, A. Maki22, , Y. MakidaY. Makida22, T. Mashimo, T. Mashimo77, S. Mihara, S. Mihara77, T. Mitsuhashi, T. Mitsuhashi77, , T. MoriT. Mori77, D. Nocol, D. Nocolòò44,,
H. NishiguchiH. Nishiguchi77, H. Okada, H. Okada88, W. Ootani, W. Ootani77, K. Ozone, K. Ozone77, R. Pazzi, R. Pazzi44, S. Ritt, S. Ritt66, , T. SaekiT. Saeki77, R. Sawada, R. Sawada77, F. Sergiampietri, F. Sergiampietri44, G. Signorelli, G. Signorelli44, V. P. Smakhtin, V. P. Smakhtin11, ,
S. SuzukiS. Suzuki88, K. Terasawa, K. Terasawa88, A. Yamamoto, A. Yamamoto22, M. Yamashita, M. Yamashita77, , K. YoshimuraK. Yoshimura22, T. Yoshimura, T. Yoshimura88
1 BINP, Novosibirsk, Russia2 KEK, Tsukaba, Japan
3 Osaka University, Osaka, Japan4 INFN, University and Scuola Normale Superiore, Pisa, Italy
5 INFN and University of Pavia, Pavia, Italy6 PSI Villigen, Switzerland
7 University of Tokyo, Tokyo, Japan8 Waseda University, Tokyo, Japan
Wataru Ootani, Wataru Ootani, ICEPP, University of TokyoICEPP, University of Tokyo NP02, Kyoto, Sep. 27-29 2002NP02, Kyoto, Sep. 27-29 2002
e e • Event signature Event signature
• Back to backBack to back
• Time coincident Time coincident
• EEe e = = EE= 52.8MeV= 52.8MeV
• Lepton-family-number nonconserving processLepton-family-number nonconserving process• Extremely small branching ratio in the standard model with finite nExtremely small branching ratio in the standard model with finite neutrino mass eutrino mass
ex.) BR(ex.) BR(ee)~)~1010-52-52 for for mm~0.05eV~0.05eV
• Sensitive to physics beyond the standard modelSensitive to physics beyond the standard model
SUSY-GUT, SUSY+νSUSY-GUT, SUSY+νR R , …, …
• Present experimental bound Present experimental bound
BR(μBR(μ ++→→ ee ++ γ) < 1.2 x 10γ) < 1.2 x 10 -- 11 11 (MEGA experiment, 1999) (MEGA experiment, 1999) • New experiment with a sensitivity of BR~10New experiment with a sensitivity of BR~10-14-14 planned at PSI planned at PSI
μ+
ee++
γ
Wataru Ootani, Wataru Ootani, ICEPP, University of TokyoICEPP, University of Tokyo NP02, Kyoto, Sep. 27-29 2002NP02, Kyoto, Sep. 27-29 2002
Physics MotivationsPhysics Motivations
• SU(5) SUSY-GUT predicts BRSU(5) SUSY-GUT predicts BR (( ee ) = ) = 1010-15-15 - 10 - 10-13-13
(SO(10) SUSY-GUT: even larger value 10(SO(10) SUSY-GUT: even larger value 10-13-13 - 10 - 10-11-11))• Small tanSmall tan excluded by LEP SUSY search excluded by LEP SUSY search
J. Hisano et al., Phys. Lett. B391 (1997) 341
Our goal
Wataru Ootani, Wataru Ootani, ICEPP, University of TokyoICEPP, University of Tokyo NP02, Kyoto, Sep. 27-29 2002NP02, Kyoto, Sep. 27-29 2002
Physics Motivations, cont’dPhysics Motivations, cont’dAfter the recent SNO measurements...After the recent SNO measurements...
SNO collaboration, Q.R.Ahamd et al., PRL89(2002)010302
SUSY+νSUSY+νRR
Our goal
• Solar Solar meas. strongly favor the LMA. meas. strongly favor the LMA.• Large tanLarge tan large large ee rate rate
J.Hisano and D.Nomura, PRD59(1999)116005J.Hisano and D.Nomura, PRD59(1999)116005
Wataru Ootani, Wataru Ootani, ICEPP, University of TokyoICEPP, University of Tokyo NP02, Kyoto, Sep. 27-29 2002NP02, Kyoto, Sep. 27-29 2002
MEG DetectorMEG Detector
• Liquid xenon photon detectorLiquid xenon photon detector
• Positron spectrometer with Positron spectrometer with
gradient magnetic field (COBRA gradient magnetic field (COBRA
spectrometer)spectrometer)
• World’s most intense DC muon World’s most intense DC muon
beam at PSIbeam at PSI
• Sensitivity down to BR~10Sensitivity down to BR~10-14-14
• Engineering/physics run will start Engineering/physics run will start
in 2004in 2004
Wataru Ootani, Wataru Ootani, ICEPP, University of TokyoICEPP, University of Tokyo NP02, Kyoto, Sep. 27-29 2002NP02, Kyoto, Sep. 27-29 2002
Sensitivity and BackgroundSensitivity and Background
• Major backgroundsMajor backgrounds
NN=1x10=1x1088/sec, /sec, TT =2.2x10 =2.2x1077sec, sec, /4/4=0.09, =0.09, =0.7,=0.7,ee=0.=0.9595
BR(BR( ++→→ ee ++ ) ~ 0.94 x 10) ~ 0.94 x 10-14-14
• Single event sensitivitySingle event sensitivity
• AccidentalAccidental CoincidenceCoincidence Michel decay(μMichel decay(μ ++→→ ee ++ ννeeννμμ) ) + random + random γγ
BBaccidental accidental ~ 5 x 10~ 5 x 10-15-15
• Radiative muon decaysRadiative muon decays μμ ++→→ ee ++ ννeeννμ μ γγ BBprompt prompt ~ 10~ 10-17-17
ΔΔEEee 0.7% (FWHM)0.7% (FWHM)
ΔΔEEγγ 1.4 – 2.0 % (FWHM)1.4 – 2.0 % (FWHM)
ΔΔeeγγ 12 – 14 mrad(FWHM12 – 14 mrad(FWHM))
ΔΔtteeγγ 0.15 nsec0.15 nsec (FWHM)(FWHM)
Proposed detector performance
These values could be changed according to the actually achieved performance of the detector.
Wataru Ootani, Wataru Ootani, ICEPP, University of TokyoICEPP, University of Tokyo NP02, Kyoto, Sep. 27-29 2002NP02, Kyoto, Sep. 27-29 2002
Beam LineBeam Line• DC muon beam rate above DC muon beam rate above 10108 8 /s/s at at E5 beam lineE5 beam line• Two beam branches (“U” and “Z”)Two beam branches (“U” and “Z”)• Comparative study of the branches Comparative study of the branches is in progress.is in progress.• Positron contamination can be Positron contamination can be reduced by:reduced by: (1) Combination of an energy degrader(1) Combination of an energy degrader and a magnetic selectionand a magnetic selection (2) Wien filter(2) Wien filter
Condition “Z”-branch “U”-branch
No degrader, transmitted to zone
3.6x108+/s
6.0x108e+/s
3.5x108+/s
1.6x109e+/s
Degrader at final focus
2.0x108+/s 3.2x107+/s
m/e ratio at Muon Peak
9 16.5
Decision on the choice of the beam Decision on the choice of the beam branch will be made after the beambranch will be made after the beam tests tests with “U”-branch in Aug.2002 and with “U”-branch in Aug.2002 and with “Z”-branch in Nov.2002with “Z”-branch in Nov.2002
prim
ary
pro
ton
be
am
Wataru Ootani, Wataru Ootani, ICEPP, University of TokyoICEPP, University of Tokyo NP02, Kyoto, Sep. 27-29 2002NP02, Kyoto, Sep. 27-29 2002
Liquid Xenon Photon Detector Liquid Xenon Photon Detector
Current designCurrent design Active volume of LXe: ~800 literActive volume of LXe: ~800 liter Scintillation light is collected Scintillation light is collected by ~800 PMTs immersed in LXeby ~800 PMTs immersed in LXe Compact PMT with metal channel dynode sCompact PMT with metal channel dynode s
tructure and quartz windowtructure and quartz window (Hamamatsu R6041Q)(Hamamatsu R6041Q)
• High light yield (75% of NaI(Tl))High light yield (75% of NaI(Tl))• Fast signals Fast signals avoid accidental pileupsavoid accidental pileups• Spatially uniform responseSpatially uniform response no need for segmentationno need for segmentation
Wataru Ootani, Wataru Ootani, ICEPP, University of TokyoICEPP, University of Tokyo NP02, Kyoto, Sep. 27-29 2002NP02, Kyoto, Sep. 27-29 2002
Photon Detector PrototypePhoton Detector Prototype
• A total of 120 liter liquid xenon (A total of 120 liter liquid xenon (active volume of 69 literactive volume of 69 liter))• Viewed by Viewed by 240 PMTs240 PMTs• Large enough to test with ~50MeVLarge enough to test with ~50MeV • LEDs and LEDs and sources ( sources (241241Am) implemented for calibrationAm) implemented for calibration
Wataru Ootani, Wataru Ootani, ICEPP, University of TokyoICEPP, University of Tokyo NP02, Kyoto, Sep. 27-29 2002NP02, Kyoto, Sep. 27-29 2002
Gamma Beam TestsGamma Beam Tests• Performance test of large prototype using high-energy gamma rays Performance test of large prototype using high-energy gamma rays • Laser Compton backscattering facility at TERAS electron storage ring Laser Compton backscattering facility at TERAS electron storage ring of AIST, Tsukuba, Japanof AIST, Tsukuba, Japan• Gamma-ray beam with energy up to 40MeVGamma-ray beam with energy up to 40MeV• Energy resolution evaluated by spread of Compton edgeEnergy resolution evaluated by spread of Compton edge• Position reconstructed by PMT output distribution with proper collimatorPosition reconstructed by PMT output distribution with proper collimator• Timing reconstructed by averaging arrival timeTiming reconstructed by averaging arrival time• Beam test in Feb. 2002 Beam test in Feb. 2002
Energy spectrum of gamma beamwith 1mm collimator (simulation)
Wataru Ootani, Wataru Ootani, ICEPP, University of TokyoICEPP, University of Tokyo NP02, Kyoto, Sep. 27-29 2002NP02, Kyoto, Sep. 27-29 2002
Beam test in Feb. 2002Beam test in Feb. 2002
• Observed amount of light from 40MeV Observed amount of light from 40MeV is smaller than expected. (~10%) is smaller than expected. (~10%)• Strong correlation between the conversion depth and Strong correlation between the conversion depth and NNpepe
• Worse position resolution than expectedWorse position resolution than expected
can be explained by strong light absorption in LXe
Position
22: conversion depth parameter: conversion depth parameter
50<2<55Energy
Wataru Ootani, Wataru Ootani, ICEPP, University of TokyoICEPP, University of Tokyo NP02, Kyoto, Sep. 27-29 2002NP02, Kyoto, Sep. 27-29 2002
MC Predictions with AbsorptionMC Predictions with Absorption
Feb02 beam test
MC:monochromatic 40MeV
Energy resolutionEnergy resolution Position resolutionPosition resolution
• MC predictions indicate MC predictions indicate abs abs < 10cm in gamma beam test in Feb. 2002< 10cm in gamma beam test in Feb. 2002• We need We need abs abs > 100cm at least for an energy resolution of a few % order > 100cm at least for an energy resolution of a few % order
Wataru Ootani, Wataru Ootani, ICEPP, University of TokyoICEPP, University of Tokyo NP02, Kyoto, Sep. 27-29 2002NP02, Kyoto, Sep. 27-29 2002
Light Absorption in LXeLight Absorption in LXeHH22O, CO, C22HH44, NH, NH33, O, O22 can strongly absorb 175nm scintillation can strongly absorb 175nm scintillation
light from LXe light from LXe Contaminations in LXe? Contaminations in LXe?
Mass spectrum for the remaining gasMass spectrum for the remaining gasin the detector vesselin the detector vessel
He
H2ON2
O2 CO2
Xe
Wataru Ootani, Wataru Ootani, ICEPP, University of TokyoICEPP, University of Tokyo NP02, Kyoto, Sep. 27-29 2002NP02, Kyoto, Sep. 27-29 2002
PurificationPurification• New circulatory purification system is installed after the beam testNew circulatory purification system is installed after the beam test in Feb.2002.in Feb.2002.• Xenon vapor is purified in Xenon vapor is purified in Zr-V-Fe getter and Oxisorb filter and Zr-V-Fe getter and Oxisorb filter and recondensed by the refrigerator and LNrecondensed by the refrigerator and LN22 during the operation of during the operation of
the detectorthe detector• Circulation speed 10-12cc liq./minuteCirculation speed 10-12cc liq./minute
Wataru Ootani, Wataru Ootani, ICEPP, University of TokyoICEPP, University of Tokyo NP02, Kyoto, Sep. 27-29 2002NP02, Kyoto, Sep. 27-29 2002
Improvement of Light YieldImprovement of Light Yield
Alpha event Alpha event Cosmic ray eventCosmic ray event
Wataru Ootani, Wataru Ootani, ICEPP, University of TokyoICEPP, University of Tokyo NP02, Kyoto, Sep. 27-29 2002NP02, Kyoto, Sep. 27-29 2002
Absorption Length EstimationAbsorption Length EstimationAbsorption length is estimated by seeing the absorption of the light fromAbsorption length is estimated by seeing the absorption of the light from the alpha source event and cosmic ray event. the alpha source event and cosmic ray event.
Cosmic ray trigger setupCosmic ray trigger setup4 x alpha source inside 4 x alpha source inside
Wataru Ootani, Wataru Ootani, ICEPP, University of TokyoICEPP, University of Tokyo NP02, Kyoto, Sep. 27-29 2002NP02, Kyoto, Sep. 27-29 2002
Absorption Length Estimation, Absorption Length Estimation, cont’dcont’d
Both measurements(CR and Both measurements(CR and ) indicate ) indicate abs abs ~100cm ~100cm
after the purificationafter the purification
Cosmic rayCosmic ray AlphaAlpha
Wataru Ootani, Wataru Ootani, ICEPP, University of TokyoICEPP, University of Tokyo NP02, Kyoto, Sep. 27-29 2002NP02, Kyoto, Sep. 27-29 2002
Positron SpectrometerPositron Spectrometer
• Thin superconducting magnet designed to form gradient magnetic fieldThin superconducting magnet designed to form gradient magnetic field• Drift chamber for positron trackingDrift chamber for positron tracking• Scintillation counters for timing measurementScintillation counters for timing measurement
COBRA spectrometerCOBRA spectrometer
Wataru Ootani, Wataru Ootani, ICEPP, University of TokyoICEPP, University of Tokyo NP02, Kyoto, Sep. 27-29 2002NP02, Kyoto, Sep. 27-29 2002
Concept of COBRA SpectrometerConcept of COBRA Spectrometer
Gradient field
Gradient field
Uniform field
Uniform field
COBRA : COnstant Bending RAdius• Constant bending radius independent of emission anglesConstant bending radius independent of emission angles
• Low energy positrons quickly swept out Low energy positrons quickly swept out
Wataru Ootani, Wataru Ootani, ICEPP, University of TokyoICEPP, University of Tokyo NP02, Kyoto, Sep. 27-29 2002NP02, Kyoto, Sep. 27-29 2002
MagnetMagnet• Five coils with three different diameter to form Five coils with three different diameter to form gradient fieldgradient field• BBcc = 1.26T, B = 1.26T, Bz=1.25mz=1.25m=0.49T@ operating current = 359A=0.49T@ operating current = 359A• Compensation coils to suppress the residual field around the LXe detectorCompensation coils to suppress the residual field around the LXe detector down to ~50Gaussdown to ~50Gauss• High-strength aluminum stabilized superconductor High-strength aluminum stabilized superconductor thin superconducting coil: thin superconducting coil: 0.20.2XX00
Wataru Ootani, Wataru Ootani, ICEPP, University of TokyoICEPP, University of Tokyo NP02, Kyoto, Sep. 27-29 2002NP02, Kyoto, Sep. 27-29 2002
Construction of the MagnetConstruction of the Magnet
Central coil
• Magnet design was finalized after detailed mechanical Magnet design was finalized after detailed mechanical calculations and related experimental tests.calculations and related experimental tests.• Winding of the cable is in progress @ Toshiba.Winding of the cable is in progress @ Toshiba.• Excitation test for the central part of the magnetExcitation test for the central part of the magnet will be performed in October 2002.will be performed in October 2002.
Central coil Gradient coil
Compensation coil
Winding of the central coil
Wataru Ootani, Wataru Ootani, ICEPP, University of TokyoICEPP, University of Tokyo NP02, Kyoto, Sep. 27-29 2002NP02, Kyoto, Sep. 27-29 2002
Positron TrackerPositron Tracker
• 17 chamber sectors aligned radially 17 chamber sectors aligned radially with 10°intervalswith 10°intervals• Two staggered arrays of drift cellsTwo staggered arrays of drift cells• Chamber gas: He-CChamber gas: He-C22HH66 mixture mixture• Vernier pattern on the cathode foil Vernier pattern on the cathode foil to determine z-positionto determine z-position
Wataru Ootani, Wataru Ootani, ICEPP, University of TokyoICEPP, University of Tokyo NP02, Kyoto, Sep. 27-29 2002NP02, Kyoto, Sep. 27-29 2002
First Prototype of the ChamberFirst Prototype of the Chamber
Resolution(Resolution())
Drift time measurementDrift time measurement 100-150100-150mm
Vernier cathod measurementVernier cathod measurement 425425mm
Charge division measurementCharge division measurement 2cm2cm
Drift velocity and drift timeDrift velocity and drift time 4-12ns4-12ns
Sr-90Sr-90
Wataru Ootani, Wataru Ootani, ICEPP, University of TokyoICEPP, University of Tokyo NP02, Kyoto, Sep. 27-29 2002NP02, Kyoto, Sep. 27-29 2002
Chambers System R&D in PSIChambers System R&D in PSI• Two prototypes are under construction at PSI.Two prototypes are under construction at PSI.
• “ “Double cathode” test chamberDouble cathode” test chamber• Two separated double-strip cathodes for Two separated double-strip cathodes for
each chamber layereach chamber layer homogeneous position sensitivityhomogeneous position sensitivity
• Test in 1 Tesla magnetic fieldTest in 1 Tesla magnetic field• “ “Charge division” test chamberCharge division” test chamber
• Charge division testCharge division test• 1m-long W(330W/m) or Steel(1200W/m) 1m-long W(330W/m) or Steel(1200W/m)
• Supporting system is also under development.Supporting system is also under development.
Wataru Ootani, Wataru Ootani, ICEPP, University of TokyoICEPP, University of Tokyo NP02, Kyoto, Sep. 27-29 2002NP02, Kyoto, Sep. 27-29 2002
Timing CounterTiming Counter
• Two layers of scintillator hodoscopes placed at right angles with each otherTwo layers of scintillator hodoscopes placed at right angles with each other Outer: Outer: timing measurementtiming measurement Inner: Inner: additional trigger informationadditional trigger information• Goal Goal timetime~ 50psec~ 50psec
Wataru Ootani, Wataru Ootani, ICEPP, University of TokyoICEPP, University of Tokyo NP02, Kyoto, Sep. 27-29 2002NP02, Kyoto, Sep. 27-29 2002
Timing Counter PrototypeTiming Counter PrototypeCORTESCORTES: Timing counter test facility with cosmic rays at INFN-Pisa: Timing counter test facility with cosmic rays at INFN-Pisa
• Scintillator bar (5cm x t1cm x 100cm long)• Telescope of 8 x MSGC• Measured resolutions time~60psec independent of incident position• time improves as ~1/√Npe use thicker counter ~t2cm
Wataru Ootani, Wataru Ootani, ICEPP, University of TokyoICEPP, University of Tokyo NP02, Kyoto, Sep. 27-29 2002NP02, Kyoto, Sep. 27-29 2002
Trigger ElectronicsTrigger Electronics
• Beam rate 10Beam rate 1088 s s-1-1
• Fast LXe energy sum >45MeV 2x10Fast LXe energy sum >45MeV 2x1033 s s-1-1
• interaction pointinteraction point• ee++ hit point in timing counter hit point in timing counter• Time correlation Time correlation -e-e++ 200 s 200 s-1-1
• Angular correlation Angular correlation 20 s20 s-1-1
• Design and simulation of type1 board completedDesign and simulation of type1 board completed
• Prototype board delivered in Pisa by this fallPrototype board delivered in Pisa by this fall
Trigger system structure
Wataru Ootani, Wataru Ootani, ICEPP, University of TokyoICEPP, University of Tokyo NP02, Kyoto, Sep. 27-29 2002NP02, Kyoto, Sep. 27-29 2002
Slow ControlSlow Control• New field bus system under development for a reliable control of New field bus system under development for a reliable control of cryogenics of LXe detector, superconducting magnet, cryogenics of LXe detector, superconducting magnet, high voltage supply high voltage supply • Low cost (typ. 20 US$ per node)Low cost (typ. 20 US$ per node)• Several prototypes have been built and tested at PSISeveral prototypes have been built and tested at PSI• SeeSee http://midas.psi.ch/mscb
Wataru Ootani, Wataru Ootani, ICEPP, University of TokyoICEPP, University of Tokyo NP02, Kyoto, Sep. 27-29 2002NP02, Kyoto, Sep. 27-29 2002
SummarySummary
• R&D work on the sub-detectors for the MEG experiment are going well.R&D work on the sub-detectors for the MEG experiment are going well.• Performance of the LXe photon detector prototype is improving thanks toPerformance of the LXe photon detector prototype is improving thanks to
the improvement of the light yield.the improvement of the light yield.• A beam test of the photon detector prototype with the purified xenonA beam test of the photon detector prototype with the purified xenon
will be performed in Oct. 2002.will be performed in Oct. 2002.• Beam line tuning with the COBRA magnet and assembly of Beam line tuning with the COBRA magnet and assembly of
the sub-detectors will start in 2003.the sub-detectors will start in 2003.• Engineering run will start in 2004.Engineering run will start in 2004.
Updated status can be seen at three mirrored sites:Updated status can be seen at three mirrored sites: http://meg.icepp.s.u-tokyo.ac.jp/ http://meg.psi.ch/ http://meg.pi.infn.it/