MEG最初の一年、その展望 東京大学素粒子物理国際研究センター 三原 智 1 Satoshi MIHARA, ICEPP Univ. of Tokyo, JSPS meeting in Matsuyama
Contents • • • Introduction MEG Detector Sensitivity and background Our schedule Summary 2 Satoshi MIHARA, ICEPP Univ. of Tokyo, JSPS meeting in Matsuyama
Introduction 3 Satoshi MIHARA, ICEPP Univ. of Tokyo, JSPS meeting in Matsuyama
μ→eγ • Lepton Flavor Violation (LFV) is strictly forbidden in SM n μ • Neutrino oscillation m – LF is not conserved – Contribute ∝ (mn/m. W)4 • Supersymmetry e e e W g ~~ Br(m eg) ∝(sinqme(mm 2 -me 2)/m 2 SUSY)2 ~ ~ – Off-diagonal terms in the slepton mass matrix Just below the current limit Br(μ→eγ) = 1. 2 x 10 -11 4 (MEGA, PRL 83(1999)83) Satoshi MIHARA, ICEPP Univ. of Tokyo, JSPS meeting in Matsuyama
Other LFV search experiments • t mg, eg – KEK, BELLE – SLAC, BABAR • m-e conversion – J-PARC, PRISM project, PRIME 5 Satoshi MIHARA, ICEPP Univ. of Tokyo, JSPS meeting in Matsuyama
MEG m eg decay search experiment at Paul Scherrer Institut Japan, Italy, Switzerland, Russia, USA 6 Satoshi MIHARA, ICEPP Univ. of Tokyo, JSPS meeting in Matsuyama
Signal and Background • Signal • Background – Radiative m decay g m m n e e • • g n – Accidental overlap Eg = mm/2 = 52. 8 Me. V Ee = mm/2 = 52. 8 Me. V q = 180 o Time coincidence n m e n g ? 7 Satoshi MIHARA, ICEPP Univ. of Tokyo, JSPS meeting in Matsuyama
Essentials • Intense muon beam – DC beam is better to reduce accidental pile-up events • Gamma Detector Liquid Xenon Detector – Good resolutions – Capability of identifying pile-up events • Positron Detector – – – COBRA spectrometer Good resolutions Low amount of material Blind to low energy positrons 8 Satoshi MIHARA, ICEPP Univ. of Tokyo, JSPS meeting in Matsuyama
PSI Proton Cyclotron Target unit 9 Proton energy: 590 Me. V Nominal operation current: 1. 8 m. A. Max > 2. 0 m. A possible. Target flask MEG Satoshi MIHARA, ICEPP Univ. of Tokyo, JSPS meeting in Matsuyama
MEG Detector • • • Liquid xenon photon detector COBRA spectrometer – Magnet, DC, TC All detector waveforms are recorded. 10 Satoshi MIHARA, ICEPP Univ. of Tokyo, JSPS meeting in Matsuyama
Beam Line Beam Transport Solenoid • • Length 10. 4 m Solid angle 150 msr Momentum acceptance (FWHM) 10 % Momentum resolution (FWHM) 2 % Target separator Trip I ASC Trip II COBRA Y Sep X BTS 11 森田裕一 “MEG実験におけるビームチューニング” 29日午後 Satoshi MIHARA, ICEPP Univ. of Tokyo, JSPS meeting in Matsuyama
Beam Line Commissioning • 2005 mid July – end August • 2005 beg November – end December – Beam Transport Solenoid (BTS) Commissioning – Bfield mapping – Phase space measurements up to end BTS – Commissioning BTS with Cryo-plant and Control system • BTS automated operation – Phase Space measurements inside COBRA • Pill scinti + APD on 3 -D measuring machine • End-caps and insertion system • Complex design He/Vacuum/N 2/Air interface • Materials minimized Al & CH 2/EVAL (background) US DS Calibration target installation 12 Satoshi MIHARA, ICEPP Univ. of Tokyo, JSPS meeting in Matsuyama
Target System • Various solutions under study – Target material • Rohacell form/CH 2 combination • Complete Rohacell • CH 2 or polystyrene Target + wire frame DC Structure Insertion Bellows 13 Satoshi MIHARA, ICEPP Univ. of Tokyo, JSPS meeting in Matsuyama
COBRA Magnet • 360 A, 1. 27 T • 0. 197 X 0 around the center Compensation coil (NC) Inner/Outer end coil (SC) Gradient coil (SC) Central coil (SC) 14 Satoshi MIHARA, ICEPP Univ. of Tokyo, JSPS meeting in Matsuyama
COBRA Magnet • Cooling by using two GMtype refrigerators Design field – No need of helium for operation • Compensation coil to reduce field strength around the xenon detector Measured field around the xenon detector • Field measurement has been completed recently 15 Satoshi MIHARA, ICEPP Univ. of Tokyo, JSPS meeting in Matsuyama
Liquid Xenon Detector • 800~900 liquid xenon • 846 PMTs immersed in the liquid • No segmentation • Why Liquid Xe ? – Good resolutions • Large light output yield • Wph(1 Me. V e) = 22. 4 e. V – Pile-up event rejection • Fast response and short decay time • ts = 4. 2 nsec, t. T=45 nsec (for electron, no E) • 西村康宏 “MEG実験用光電子増倍管の液体キセノン中における LEDを用いた利得解析と現状” 27日午後 16 Satoshi MIHARA, ICEPP Univ. of Tokyo, JSPS meeting in Matsuyama
Depth Reconstruction • Broadness of light distribution at the entrance side waveform 17 shallow deep Satoshi MIHARA, ICEPP Univ. of Tokyo, JSPS meeting in Matsuyama
PMT test in LXe • All PMTs were tested in LXe before installing to the detector – Pisa LXe PMT test facility – Xenon Detector Large Prototype • QE, Gain, response linearity • All information is stored in a database for future use. No zener with zener Bad 18 Satoshi MIHARA, ICEPP Univ. of Tokyo, JSPS meeting in Matsuyama
Construction Status • Cryostat Construction in progress in Italy • Delivery in June • PMT installation and setup after that • Ready in September 19 Satoshi MIHARA, ICEPP Univ. of Tokyo, JSPS meeting in Matsuyama
DC • • Position resolutions (~300 mm) for both r and z. Vernier pad readout for z measurement Low amount of material Need very precise pressure control ~1 Pa 20 Satoshi MIHARA, ICEPP Univ. of Tokyo, JSPS meeting in Matsuyama
TC APD F. E. Board APD Cooled Support TC Final Design Scintillating Fibers (Phi Counter) PM ladder Board & cabling Main Support • A PLASTIC SUPPORT STRUCTURE ARRANGES THE SCINTILLATOR BARS AS REQUESTED BC 404 Scintillator slab • THE BARS ARE GLUED ONTO THE SUPPORT • INTERFACE ELEMENTS ARE GLUED ONTO THE BARS AND SUPPORT THE FIBRES Scintillator Housing • FIBRES ARE GLUED AS WELL 21 • TEMPORARY ALUMINIUM BEAMS ARE USED TO HANDLE THE DETECTOR DURING INSTALLATION • PTFE SLIDERS WILL ENSURE A SMOOTH MOTION ALONG THE RAILS PM-Scintillator Coupling Satoshi MIHARA, ICEPP Univ. of Tokyo, JSPS meeting in Matsuyama
TC Assembly • PMT test completed • Assembly test started 22 Satoshi MIHARA, ICEPP Univ. of Tokyo, JSPS meeting in Matsuyama
Electronics 23 Satoshi MIHARA, ICEPP Univ. of Tokyo, JSPS meeting in Matsuyama
16 Type 1 . . . 16 Type 1 Drift chambers 16+16 channels Auxiliary devices 16 channels 2 boards 14 x 48 Type 2 5+5+2 boards 2 x 48 1 board 9 x 48 4 2 x 48 Type 2 . . Timing counters curved (640 APDs) 8 in 1 u/d stream (30 x 2 PMTs) 14 boards 4 . LXe front face (216 PMTs) LXe lateral faces back (216 PMTs) 4 in 1 lat. (144 x 2 PMTs) 4 in 1 up/down (54 x 2 PMTs) 4 in 1 . . . Trigger Tree 16 Type 1 1 board 9 boards 9 x 48 1 x 48 4 Type 2 2 boards 16 Type 1 16 1 board 2 x 48 4 16 Type 1 4 1 x 48 24 Satoshi MIHARA, ICEPP Univ. of Tokyo, JSPS meeting in Matsuyama
Trigger Electronics • PCB production finished • Currently board mounting in progress • Ready to install in June Type 2 Type 1 25 Satoshi MIHARA, ICEPP Univ. of Tokyo, JSPS meeting in Matsuyama
DAQ/Waveform Digitizer R. Paoletti, N. Turini, R. Pegna MAGIC collaboration PSI GVME Board FPGA with 4 Power-PC DRS USB 26 Satoshi MIHARA, ICEPP Univ. of Tokyo, JSPS meeting in Matsuyama
DRS – Domino Ring Sampler 27 Satoshi MIHARA, ICEPP Univ. of Tokyo, JSPS meeting in Matsuyama
Waveform Analysis • • • Q, T evaluation from waveforms Pile-up rejection Waveform fitting is very CPU time consuming Peak search method DT=50 ns. DT=15 ns simulation Differential method • Constant fraction simulation • Fraction: 0. 3, delay 10 nsec 28 • 内山雄祐 “MEG実験用液体キセノン検出器の波形解析による性 能評価” 27日午後 11 Me. V + 42 Me. V Satoshi MIHARA, ICEPP Univ. of Tokyo, JSPS meeting in Matsuyama
Background and Sensitivity 4 E 7 sec Energy deposit/ 52. 8 Me. V PILE UP EVENTS RD+RD dominant # of Background events, 2 years RUN δθeγ= 14 mrad 100 psec 1 Muon stopping rate [/sec] 29 Satoshi MIHARA, ICEPP Univ. of Tokyo, JSPS meeting in Matsuyama
How Far Can We Go? • Expected sensitivity at 90% C. L. BEAMTIME=4 E 7 sec 2 year muon beam intensity (/sec) YEAR 2006 1 MONTH BEAMTIME muon beam intensity (/sec) 30 Satoshi MIHARA, ICEPP Univ. of Tokyo, JSPS meeting in Matsuyama
Schedule • MEG beam time; Apr-Jun, Aug-Dec • DC/TC run with beam; Sep • LXe – Setup; -Sep~Oct, Calibration run; ~Nov – – Ready in Nov • DAQ/Trigger; Ready in Jun • Ready to start DAQ; ~mid Nov 31 Satoshi MIHARA, ICEPP Univ. of Tokyo, JSPS meeting in Matsuyama
Summary • MEG starts in 2006 • Detectors are getting ready • Analysis/online softwares also • For further information, visit http: //meg. icepp. s. utokyo. ac. jp • 澤田龍 “汎用データ解析ソフトウェア生成ツールROME&ARGUS” 30日午後 32 Satoshi MIHARA, ICEPP Univ. of Tokyo, JSPS meeting in Matsuyama
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