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

11

Data taking started in september 2007

Full apparatus

CW beam line

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