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MEG
1
e search at PSI: SUGRA indications
• SUSY SU(5) predictions
BR (e) 10-14 10-
13
• SUSY SO(10) predictions
BRSO(10) 100 BRSU(5) R. Barbieri et al., Phys. Lett. B338(1994) 212
R. Barbieri et al., Nucl. Phys. B445(1995) 215
LFV induced by slepton mixing
Our goal
Experimental limit
combined LEP results favour tan>10 -5410R in the Standard Model !!
MEG
2
Experimental method
1m
e+
Liq. Xe Scin tilla tionDetector
Drift Cham ber
Liq. Xe Scin tilla tionDetector
e+
Tim ing Counter
Stopping TargetThin S uperconducting Coil
M uon Beam
Drift Cham ber
Easy signal selection with + at rest
e+ + Ee = E = 52.8 MeV
e = 180°Detector outline
• Stopped beam of 3 107 /sec in a 150 m target
• Liquid Xenon calorimeter for detection (scintillation)
- fast: 4 / 22 / 45 ns
- high LY: ~ 0.8 * NaI
- short X0: 2.77 cm
• Solenoid spectrometer & drift chambers for e+ momentum
• Scintillation counters for e+ timing
MEG
3
Univ. of TokyoY. Hisamatsu, T. Iwamoto, T. Mashimo, S. Mihara, T. Mori, Y. Morita, H. Natori, H. Nishiguchi, Y.
Nishimura, W. Ootani, K. Ozone, R. Sawada, Y. Uchiyama, S. YamashitaKEK
T. Haruyama, K. Kasami, A. Maki, Y. Makida, A. Yamamoto, K. YoshimuraWaseda Univ.
K. Deguchi, T. Doke, J. Kikuchi, S. Suzuki, K. Terasawa
INFN PisaA. Baldini, C. Bemporad, F. Cei, C.Cerri, L.del Frate, L. Galli, G. Gallucci, M. Grassi, F. Morsani, D.
Nicolò, A. Papa, F. Raffaelli, F. Sergiampietri, G. SignorelliINFN and Univ. of Genova
S. Cuneo, M. de Gerone, S. Dussoni, F. Gatti, S. Minutoli, P. Musico, P. Ottonello, R. ValleINFN and Univ. of Pavia
G. Boca, P. W. Cattaneo, G. Cecchet, A. De Bari, M. RossellaINFN and Univ. of Roma I
A. Barchiesi, G. Cavoto, G. Piredda, C. Voena, D. ZanelloINFN and Univ. of Lecce
P. Creti, G. Palama’, M. Panareo
Paul Scherrer InstituteJ. Egger, P.-R. Kettle, M. Hildebrandt, S.Ritt
BINP NovosibirskL. M. Barkov, A. A. Grebenuk, D. N. Grigoriev, B. I. Khazin, N. M. Ryskulov
JINR DubnaA. Korenchenko, N. Kravchuk, A. Moiseenko, D. Mzavia
Univ. of California, IrvineW. Molzon, M. Hebert, P. Huwe, J. Perry, V. Tumakov, F. Xiao, S. Yamada
MEGMEG
~40 FTEs ~40 FTEs
The MEG collaboration
MEG
4
COnstant Bending RAdius (COBRA) spectrometer (KEK)
Gradient field Uniform field
• Constant bending radius independent of emission angles
• High pT positrons quickly swept out
Gradient field Uniform field
• Bc = 1.26T current = 359A• Five coils with three different diameters • Compensation coils to suppress the stray field around the
LXe detector• High-strength aluminum stabilized superconductor
thin magnet (1.46 cm Aluminum, 0.2 X0)
No quench during 4 months
of 2007 run
MEG
5
Positron Tracker (PSI)
• 17 chamber sectors aligned radially with 10°intervals
• Two staggered arrays of drift cells• Chamber gas: He-C2H6 mixture• Vernier pattern to measure z-
position made of 15 m kapton foils
(X,Y) ~200 m (drift time) (Z) ~ 800 m (charge divisionvernier strips)
goalsproved in the experiment
MEG
6
Positron Timing Counter (Pavia + Genova + Roma 1 )
• One (outer) layer of scintillator read by PMTs : timing•One inner layer of scintillating fibers read by APDs: trigger (the long. Position
is needed for a fast estimate of the positron direction)• time~ 40 psec (100 ps FWHM) reached in tests
BC404
5 x 5 mm2
MEG
7
• 800 l of Liquid Xe
• ~800 PMT immersed in LXe
• Only scintillation light
• High luminosity
• Unsegmented volume
Liquid Xe calorimeter (Pisa + Tokyo + KEK)
FWHM =FWHM =4.8 ± 0.3%4.8 ± 0.3%
55 MeV
R<1.5cm
40 MeV and 1 mm collimator
•Measured position and energy resolutions with a 100 liters prototype
• Cryostat
• 150 ps FWHM timing resolution proved
MEG
8
17.6 MeV /ER = 7.5 10-2 measured
with a NaI
14.6 MeV
6.13 MeV
LiF target Daily calibrations
Daily calibrations by means of a 1 MeV Cockroft-Walton proton accelerator and changeable targets (Pisa)
MEG
9
Trigger Electronics (Pisa)
Beam rate 108
s-1
Fast LXe energy sum > 45MeV2103 s-1
g interaction point (PMT of max charge)
e+ hit point in timing counter
time correlation – e+ 200 s-1
angular correlation – e+ 20 s-1
•Uses easily quantities:
energy
•Positron- coincidence in time and direction
•Built on a FADC-FPGA architecture
•More complex algorithms implementable
1 board
2 VME 6U
1 VME 9U
Type2
Type2
LXe inner face
(312 PMT)
. .
. 20 boards
20 x 48
Type1Type1
Type1
16
3
Type2
2 boards
. . .
10 boards
10 x 48
Type1Type1
Type1
16
3
LXe lateral faces
(488 PMT: 4 to 1 fan-in)
Type2
1 board
. . .
12 boards
12 x 48
Type1Type1
Type1
16
3
Timing counters
(160 PMT) Type2Type2
2 boards2 x 48
4 x 48
2 x 48
MEG
10
Readout electronics (PSI): Domino Ring Sampler (DRS chip)
• Analog Waveform digitizing for all channels
• Custom domino sampling chip designed at PSI• 2 GHz sampling speed
• Sampling depth 1024 bins
• Readout similar to trigger
2.5 GHz
Set of 1024 capacitors40 MHz 11 bit
TC signals digitization
MEG
12
http://meg.pi.infn.it : in italianhttp://meg.psi.ch : official home page
http://meg.pi.infn.it : in italianhttp://meg.psi.ch : official home page
Time Scale
• Goal: significant result before entering the LHC era
• Measurements and detector simulation show that it is possible to reach a sensitivity to BR =10-13 for e and possibly below… in 3 years of data taking
More details at
1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010
Planning R & D Assembly Data Taking
nownowLoILoI
ProposalProposal