MEG e search at PSI SUGRA indications LFV

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MEG �e search at PSI: SUGRA indications LFV induced by slepton mixing Experimental limit

MEG �e search at PSI: SUGRA indications LFV induced by slepton mixing Experimental limit • SUSY SU(5) predictions Our goal BR ( e ) 10 -14 10 -13 • SUSY SO(10) predictions BRSO(10) 100 BRSU(5) R. Barbieri et al. , Phys. Lett. B 338(1994) 212 combined LEP results favour tanb>10 R. Barbieri et al. , Nucl. Phys. B 445(1995) 215 in the Standard Model !! 1

MEG Experimental method Easy signal selection with + at rest qe = 180° e

MEG Experimental method Easy signal selection with + at rest qe = 180° e + + Detector outline • Stopped beam of 3 107 /sec in a 150 m target • Liquid Xenon calorimeter for detection (scintillation) Ee = E = 52. 8 Me. V - fast: 4 / 22 / 45 ns - high LY: ~ 0. 8 * Na. I - short X 0: 2. 77 cm • Solenoid spectrometer & drift chambers for e+ momentum • Scintillation counters for e+ timing 2

MEG The MEG collaboration INFN & Genova University S. Dussoni, F. Gatti, P. Ottonello,

MEG The MEG collaboration INFN & Genova University S. Dussoni, F. Gatti, P. Ottonello, D. Pergolesi, R. Valle INFN & Lecce University S. Spagnolo, C. Chiri, P. Creti, C. Gatto, G. Marsella, G. Palama’, M. Panareo, G. Tassielli INFN & Pavia University A. de Bari, P. Cattaneo, G. Cecchet, G. Nardo’, M. Rossella INFN & Pisa University A. Baldini, C. Bemporad, F. Cei, M. Grassi, F. Morsani, D. Nicolo’, A. Papa, R. Pazzi, F. Raffaelli, F. Sergiampietri, G. Signorelli INFN Roma I D. Zanello ICEPP, University of Tokyo Y. Hisamatsu, T. Iwamoto, T. Mashimo, S. Mihara, T. Mori, H. Natori, H. Nishiguchi, W. Ootani, K. Ozone, R. Sawada, Y. Uchiyama, S. Yamada, S. Yamashita KEK, Tsukuba T. Haruyama, A. Maki, Y. Makida, A. Yamamoto, K. Yoshimura Waseda University T. Doke, J. Kikuchi, H. Okada, S. Suzuki, K. Terasawa, M. Yamaguchi PSI, Villigen J. Egger, P. Kettle, M. Hildebrandt, S. Ritt, M. Schneebeli Budker Institute, Novosibirsk L. M. Barkov, A. A. Grebenuk, D. G. Grigoriev, B, Khazin, N. M. Ryskulov 3

MEG Detector Construction Switzerland Russia Drift Chambers Beam Line DAQ LXe Tests Purification Italy

MEG Detector Construction Switzerland Russia Drift Chambers Beam Line DAQ LXe Tests Purification Italy Japan e+ counter (Pv+Ge) Trigger (Pisa) LXe Calorimeter(Pisa) Splitters (Lecce) LXe Calorimeter, Spectrometer’s magnet 4

MEG COnstant Bending RAdius (COBRA) spectrometer • High p. T positrons quickly swept out

MEG COnstant Bending RAdius (COBRA) spectrometer • High p. T positrons quickly swept out Gradient field Uniform field • Constant bending radius independent of emission angles Gradient field Uniform field • Bc = 1. 26 T current = 359 A • 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 X 0) 5 Ready: at PSI !!

MEG Positron Tracker (PSI) • 17 chamber sectors aligned radially with 10°intervals • Two

MEG Positron Tracker (PSI) • 17 chamber sectors aligned radially with 10°intervals • Two staggered arrays of drift cells • Chamber gas: He-C 2 H 6 mixture • Vernier pattern to measure z-position made of 15 m kapton foils goals (X, Y) ~200 m (drift time) (Z) ~ 300 m (charge division OK To be proved in mag. field 6 vernier strips)

MEG Positron Timing Counter (Pavia + Genova + Roma ) BC 404 • One

MEG Positron Timing Counter (Pavia + Genova + Roma ) BC 404 • One (outer) layer of scintillator read by PMTs : timing • One inner layer of scintillating fibers read by APDs: trigger (the long. Position 5 x 5 mm 2 is needed for a fast estimate of the positron direction) • Goal time~ 40 psec (100 ps FWHM) reached in tests 7

MEG Liquid Xe calorimeter (Pisa + Tokyo + KEK) • • • 800 l

MEG Liquid Xe calorimeter (Pisa + Tokyo + KEK) • • • 800 l of Liquid Xe ~800 PMT immersed in LXe Only scintillation light High luminosity Unsegmented volume 40 Me. V and 1 mm collimator 55 Me. V R<1. 5 cm FWHM = 4. 8 ± 0. 3% • Measured position and energy resolutions with a 100 liters prototype • Cryostat in construction • 150 ps FWHM timing resolution proved 8

MEG Trigger Electronics (Pisa) • Positron- coincidence in time and direction • Built on

MEG Trigger Electronics (Pisa) • Positron- coincidence in time and direction • Built on a FADC-FPGA architecture 3 Type 1 LXe lateral faces (488 PMT: 4 to 1 fan-in) . . • energy 16 20 boards 20 x 48 . LXe inner face (312 PMT) . . . • Uses easily quantities: 16 3 Type 1 10 boards 1 board 12 boards 2 103 s-1 g interaction point (PMT of max charge) e+ hit point in timing counter v time correlation – e+ v angular correlation – e+ 20 s-1 200 s-1 9 3 Type 1 1 board 12 x 48 2 boards . . 16 4 x 48 10 x 48 . v Beam rate v Fast LXe energy sum > 45 Me. V Type 2 • More complex algorithms implementable Timing counters (160 PMT) 108 s-1 2 boards Type 2 2 x 48 2 VME 6 U 1 VME 9 U Prototype board tested at PSI

MEG Readout electronics (PSI): Domino Ring Sampler (DRS chip) Set of 1024 capacitors 40

MEG Readout electronics (PSI): Domino Ring Sampler (DRS chip) Set of 1024 capacitors 40 MHz 11 bit 2. 5 GHz • Analog Waveform digitizing for all channels • Custom domino sampling chip designed at PSI • 2. 5 GHz sampling speed @ 40 ps timing resolution • Sampling depth 1024 bins • Readout similar to trigger raw • Spike structure will be simply fixed by re-programming FPGA on the board. 10 Prototype tested with 55 Me. V photons in the 100 l prototype After calibrations

MEG Sensitivity Summary Detector parameters Cuts at 1, 4 FWHM Signal Single Event Sensitivity

MEG Sensitivity Summary Detector parameters Cuts at 1, 4 FWHM Signal Single Event Sensitivity Backgrounds Upper Limit at 90% CL 4 10 -14 2 10 -14 3 10 -15 BR ( e ) 1 10 -13 11

MEG Sensitivity and time schedule • Total measurement time: 2 years (50% duty cycle

MEG Sensitivity and time schedule • Total measurement time: 2 years (50% duty cycle of PSI beam) • One e event observed if BR = 4 x 10 -14 • If no event observed upper BR limit at 90% CL = 10 -13 Discovery: 4 events (P = 2 10 -3) correspond to BR = 2 10 -13 • Final prototypes being tested • Full scale Drift Chamber • Time profile Lo. I Proposal Planning 1998 1999 2000 Revised document R&D 2001 2002 now Assembly 2003 2004 2005 Data Taking 2006 2007 http: //meg. psi. ch http: //meg. pi. infn. it http: //meg. icepp. s. u-tokyo. ac. jp More details at 12