Introduction MEG COMET Other related expts at J-PARC Summary
20/Feb/2010Satoshi MIHARA KEK-PH102
Slide 3
20/Feb/2010Satoshi MIHARA KEK-PH10 Neutrino Mixing (confirmed)
Charged Lepton Mixing (not observed yet) Sensitive to new Physics
beyond the Standard Model Very Small (10 -52 ) e e ?? Soon! e e ~ B
~ mixing LFV diagram in SUSY Large top Yukawa coupling ~ LFV
diagram in Standard Model e mixing e W (m /m W ) 4 3
Slide 4
Muon discovery in 1937 Order of 10 improvement in 50 year Best
limit Br( e) < 1.2x10 -11 (MEGA) Ti eTi < 7x10 -13 (SINDRUM
II) Strong physics motivation Neutrino oscillation SUSY GUT
20/Feb/2010Satoshi MIHARA KEK-PH104
20/Feb/2010Satoshi MIHARA KEK-PH10 cLFV search is as important
as high-energy frontier experiments (and oscillation measurements)
to find a clue to understand SUSY-GUT Neutrino See-saw MEG ( e
search at PSI) is expected to reach and go beyond the current limit
pretty soon Need other experiment(s) to confirm it Using different
physics process (with better sensitivity)! COMET (COherent Muon
Electron Transittion) Submitted a proposal to J-PARC in 2008 and a
CDR in 2009, and obtained Stage-1 approval in July 2009 6
Slide 7
e decay search experiment at PSI 20/Feb/2010Satoshi MIHARA
KEK-PH107
Slide 8
8 Aiming at observing e event with a sensitivity of ~10 -13
Normal muon decay: e Radiative muon decay: e 20/Feb/2010Satoshi
MIHARA KEK-PH10
Slide 9
9 High intensity muon beam DC is better than plused Large
acceptance of the detector system Good detector resolutions to
suppress background e 180 e e ? 52.8MeV 20/Feb/2010Satoshi MIHARA
KEK-PH10
Slide 10
Muon Beam PiE5 muon beam line 1.15x10 8 + s -1 at the detector
entrance at 1.8mA, 4cm Tg Photon Detector 900 liter liquid xenon
846 PMTS in the liquid Cooling with a PTR purification Positron
Detector COBRA spectrometer Low-mass drift chamber High resolution
timing counter 1020/Feb/2010Satoshi MIHARA KEK-PH10
Slide 11
Proposal submitted 1999 Detector R&D and construction
1998-2007 Engineering Run end of 2007 Physics run 2008 Physics
Result DAQ upgrade & problem fix during shutdown in 2009
Physics run 2009 Result Prospect 20/Feb/2010Satoshi MIHARA
KEK-PH1011
Slide 12
20/Feb/2010Satoshi MIHARA KEK-PH1012
Slide 13
MEG successfully started first physics data acquisition
12/Sep/2008 3x10 7 muon/sec with 2mA primary proton current on 4cm
target Total live time 3.4x10 6 sec 9.4x10 13 muon stops on the
target Total 139TB data on disk 13 Live time : 3.410 6 sec Total
9.410 13 muons on target t Polyester/Rohacell target Parasitic Run:
19 th May- 3 rd July ~ 7 weeks Beam Tests/Tuning (4.5 weeks) Beam
Tests/Tuning (4.5 weeks) Full Run Part 1: 11 th July 31 st August
~7 weeks CEX 21 st July 31 st August (6 weeks) CEX 21 st July 31 st
August (6 weeks) Full Run Part 2: 1 st September 23 rd December ~16
weeks Pre-Physics Data (~ 3 weeks) Pre-Physics Data (~ 3 weeks)
Physics Data Part1 35 Days Physics Data Part1 35 Days MEG
Maintenance/Repair ~ 7 Days MEG Maintenance/Repair ~ 7 Days Physics
Data Part 2 43.5 Days Physics Data Part 2 43.5 Days Mini-CEX ~ 7
Days Mini-CEX ~ 7 Days TBytes MEG 2008 Run DATA Taken 139 TB
20/Feb/2010Satoshi MIHARA KEK-PH10
Slide 14
Pre-selection and blinding Data reduction: 84% Hidden signal
box on (E, t e ) Event data falling in the blind box is
automatically separated (and password protected) and written to a
different file from other events All analysis procedure is defined
and fixed without using hidden data Analysis box is defined for the
likelihood analysis 20/Feb/2010Satoshi MIHARA KEK-PH1014
Pre-selection box Analysis box Blinding box T(Gamma) - T(Positron)
[nsec] E(Gamma) [MeV]
Slide 15
20/Feb/2010Satoshi MIHARA KEK-PH1015 and also for background
study
Slide 16
Track reconstruction with the Kalman filter technique Energy
scale and resolution are evaluated by fitting the Michel spectrum
at 52.8MeV Resolution function with core and tail components Core :
374keV (60%), tails: 1.06 MeV (33%) and 2.00MeV (7%)
1620/Feb/2010Satoshi MIHARA KEK-PH10
Slide 17
Calibration using Laser data CW Boron data CEX run data
Photon-Positron Relative time t e Positron time measured by TC is
corrected by the time-of-flight Photon time by the time-of- flight
(depth reconstruction important) RMD peak is clearly visible
40
