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MEG Status and Prospects

MEG Status and Prospects. Toshiyuki Iwamoto Paul Scherrer Institute. Physics. m  e g Lepton flavor violating process Clear evidence of new physics beyond SM Explore SUSY-GUT/seesaw Current Experimental limit MEGA Br (m-> e g) ~ 1.2x10 -11 MEG sensitivity Br (m- > e g ) ~ 10 -13.

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MEG Status and Prospects

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  1. MEG Status and Prospects Toshiyuki Iwamoto Paul Scherrer Institute

  2. Physics • m  e g • Lepton flavor violating process • Clear evidence of new physics beyond SM • Explore SUSY-GUT/seesaw • Current Experimental limit • MEGA Br(m->eg) ~ 1.2x10-11 • MEG sensitivityBr(m->eg) ~ 10-13 10-11 MEGA 10-13 MEG J. Hisano and D. Nomura, 1998 Toshiyuki Iwamoto, The 6th KEK Topical Conference, 6~8 Feb. 2007

  3. n n e+ e+ n m+ m+ 52.8MeV g g 52.8MeV 180° e+ ? m+ g n Sensitivity Signal event • Signal • clear two body decay • Background • Radiativemdecay : m+ e+nm neg< 10-14 • Accidental overlap: m en n+ randomg~ 10-14 • To reject these background, • energy, timing and vertex resolution • pile-up rejection from waveform analysis Radiative decays Accidental Detector resolution Sensitivity DEg= 5% DEe = 0.9% dteg= 100ps dqeg= 23mrad m+beam rate : 0.3x108/s Measurement time : 2 years Background event : 0.5 Br(m->eg) < 1.5x10-13 dominant Toshiyuki Iwamoto, The 6th KEK Topical Conference, 6~8 Feb. 2007

  4. Detector Approved in 1999 at PSI in Switzerland, Physics run in 2007 Japan, Italy, Switzerland, Russia, and USA collaboration e+ : COBRA spectrometer g : liquid xenon detector Toshiyuki Iwamoto, The 6th KEK Topical Conference, 6~8 Feb. 2007

  5. Detector Drift chamber 590 MeV proton Ring Cyclotron COBRA magnet w/ graded B field Photon detector Timing counter Toshiyuki Iwamoto, The 6th KEK Topical Conference, 6~8 Feb. 2007

  6. Beam Line PSI Proton Cyclotron 590MeV, >1.8mA Most intense DC beam ~108m/s accidental coincidence is dominant  lower m rate is better  DC beam surface muon beam ~ 28MeV/c m+ to avoid capture inside stopping target Beam spot size ~11mm at target 28MeV/c Toshiyuki Iwamoto, The 6th KEK Topical Conference, 6~8 Feb. 2007

  7. COBRA Spectrometer Compensation coil Constant Bending Radius spectrometer Gradient magnetic field, 1.27T at z = 0, I = 360A I = 200A COBRA magnet Photon detector < 50G Toshiyuki Iwamoto, The 6th KEK Topical Conference, 6~8 Feb. 2007

  8. Drift Chamber 16 chambers arranged radially with 10°interval Position resolution ~300mmfor both r and z Momentum resolution ~ 0.4% Low material (multiple scattering suppression) Toshiyuki Iwamoto, The 6th KEK Topical Conference, 6~8 Feb. 2007

  9. Drift chamber design z r Toshiyuki Iwamoto, The 6th KEK Topical Conference, 6~8 Feb. 2007

  10. Timing Counter • Two layers of scintillators: • Outer layer, plastic scintillator read out by PMTs: • timing measurement • Inner layer, scintillation fiber read out with APDs: • z-measurement • Obtained goalst ~40ps (100ps FWHM) z f Toshiyuki Iwamoto, The 6th KEK Topical Conference, 6~8 Feb. 2007

  11. Xenon detector 900l liquid xenon 846 2” PMT directly into Liquid Scintillation only : high light output, fast response  good resolution Energy, position and timing ofgmeasured Waveform digitization  to reject pile-up events R&D : low temperature (160K), VUV light, H2O purification, and performance test by 70 liter size prototype g Toshiyuki Iwamoto, The 6th KEK Topical Conference, 6~8 Feb. 2007

  12. PMT Total : 14.2MW Q.E. : ~15% Photocathode : K-Cs-Sb Metal channel dynode, 12 stages Silica window (for UV light) Compact, and low heat load Tolerance up to 100G magnetic field Al strip to keep surface resistance at low temp. Zener diode for high rate background Toshiyuki Iwamoto, The 6th KEK Topical Conference, 6~8 Feb. 2007

  13. After purification 1m 2.5m Before purification Purification • Gas & Liquid phase purification tested • Metal getter (zirconium) by gas ~0.5l/h • Molecular sieves by liquid ~100l/h Toshiyuki Iwamoto, The 6th KEK Topical Conference, 6~8 Feb. 2007

  14. Energy (MeV) Opening angle (q) Xenon detector performance 83MeV p-(at rest) + p ->p0+ n,p0(28MeV/c) -> g + g 55, 83MeV monochromatic energy calibration H2 target Prototype LXe 55MeV LYSO g g NaI p- Toshiyuki Iwamoto, The 6th KEK Topical Conference, 6~8 Feb. 2007

  15. 5% 1% Energy resolution vs. Energy Energy Resolution (s) [%] Xenon detector performance Energy distribution @ 55MeV • = 1.23 ±0.09 % FWHM=4.8 % Timing distribution 110 psec Expected Performance Energy : 5% (FWHM) Timing : 150 psec (FWHM) Vertex : 9mm (FWHM) 110 - 64 (LYSO) - 61 (Beam) = 65psec Toshiyuki Iwamoto, The 6th KEK Topical Conference, 6~8 Feb. 2007

  16. Liquid xenon system Liquid xenon detector gas purifier Refrigerator Liquid purifier 250l gas xenon tank x 8 1000l liquid xenon storage tank Toshiyuki Iwamoto, The 6th KEK Topical Conference, 6~8 Feb. 2007

  17. Detector Construction (xenon) top outer side inner The performance of all PMTs checked in the liquid xenon before installation After PMT installation into holders, HV set on for all PMTs Toshiyuki Iwamoto, The 6th KEK Topical Conference, 6~8 Feb. 2007

  18. Calibration method • Gain monitor : LED • Q.E. : 241Amasource • Energy • 55, 83, and 129 MeVg fromp-pp0n, p02g • Ni thermal neutron capture 9MeV • Proton accelerator • Li(p,)Be 17.6MeV resonant at Ep= 440 keV=14 keV peak = 5 mb 3x3 NaI array 9 MeV Nickelg-line 17.6 MeV Li(p,g)Be-line LH2 target 55, 83, and 129 MeVg Toshiyuki Iwamoto, The 6th KEK Topical Conference, 6~8 Feb. 2007

  19. Positron spectrometer commissioning run in 2006 • Beam • COBRA spectrometer • DAQ/Trigger • LXe detector not ready Drift chamber Timing counter Toshiyuki Iwamoto, The 6th KEK Topical Conference, 6~8 Feb. 2007

  20. Commissioning run result • Beam • 108 m+/s confirmed • Spot size sx ~ sy ~ 11mm on target • DC • 8 of 16 chambers available • Successfully operated at highest intensity • TC • Full counters without z-measuring fiber counter • DAQ • Trigger electronics worked • DRS waveform data taken • Online DAQ software also worked Toshiyuki Iwamoto, The 6th KEK Topical Conference, 6~8 Feb. 2007

  21. Plan for Year 2007 and After Run 2007 First half: complete beam tuning and COBRA spectrometer run Second half: start full MEG run as soon as calorimeter is ready Mid-2007 – 2009 MEG full DAQ 2010 – Detector upgrade / decay positron angular measurement Toshiyuki Iwamoto, The 6th KEK Topical Conference, 6~8 Feb. 2007

  22. Summary • Physics run will start this year. • All detector components except for liquid xenon were installed and tested in the commissioning run at the end of last year. • A few months data will exceed MEGA limit • 2 years DAQ to reach 10-13 sensitivity Toshiyuki Iwamoto, The 6th KEK Topical Conference, 6~8 Feb. 2007

  23. END Toshiyuki Iwamoto, The 6th KEK Topical Conference, 6~8 Feb. 2007

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