MEG Status of the MEG experiment http meg

MEG Status of the MEG experiment http: //meg. pi. infn. it A. M. Baldini INFN Pisa nfac 03 -N. Y. June 6 th 2003 1

MEG Layout of this talk • • • Physics motivations General description of the experiment Detectors R&D Sensitivity of the experiment Time schedule nfac 03 -N. Y. June 6 th 2003 2

MEG SUGRA indications LFV induced by finite slepton mixing through radiative corrections 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 R. Barbieri et al. , Nucl. Phys. B 445(1995) 215 combined LEP results favour tanb>10 nfac 03 -N. Y. June 6 th 2003 3

MEG Combined LEP experiments: SUGRA MSSM nfac 03 -N. Y. June 6 th 2003 4

MEG SO 10 nfac 03 -N. Y. June 6 th 2003 5

MEG Connection with n-oscillations Additional contribution to slepton J. Hisano, mixing from V 21 (the matrix element responsible for solar neutrino deficit) N. Nomura, Phys. Rev. D 59 (1999) tan(b)=30 tan(b)=1 Experimental limit After SNO Our goal in the Standard Model !! nfac 03 -N. Y. June 6 th 2003 6 After Kamland

MEG m+ �e+ Experiments Lab. Year Upper limit Experiment or Auth. PSI 1977 < 1. 0 10 -9 A. Van der Schaaf et al. TRIUMF 1977 < 3. 6 10 -9 P. Depommier et al. LANL 1979 < 1. 7 10 -10 W. W. Kinnison et al. LANL 1986 < 4. 9 10 -11 Crystal Box LANL 1999 < 1. 2 10 -11 MEGA PSI ~2005 ~ 10 -13 MEG Two orders of magnitude improvement is required: tough experimental challenge! nfac 03 -N. Y. June 6 th 2003 7 Comparison with other LFV searches:

MEG The MEG collaboration INFN & Genova University S. Dussoni, F. Gatti, D. Pergolesi, R. Valle INFN & Lecce University G. Cataldi, S. Spagnolo, C. Chiri, P. Creti, F. Grancagnolo, M. Panareo 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’, R. Pazzi, F. Raffaelli, F. Sergiampietri, G. Signorelli INFN Roma I D. Zanello ICEPP, University of Tokyo T. Mashimo, S. Mihara, T. Mitsuhashi, T. Mori, H. Nishiguchi, W. Ootani, K. Ozone, T. Saeki, R. Sawada, S. Yamashita KEK, Tsukuba T. Haruyama, A. Maki, Y. Makida, A. Yamamoto, K. Yoshimura Osaka University Y. Kuno Waseda University T. Doke, J. Kikuchi, H. Okada, S. Suzuki, K. Terasawa, M. Yamashita, T. Yoshimura PSI, Villigen J. Egger, P. Kettle, H. Molte, S. Ritt Budker Institute, Novosibirsk L. M. Barkov, A. A. Grebenuk, D. G. Grigoriev, B, Khazin, N. M. Ryskulov nfac 03 -N. Y. June 6 th 2003 8

MEG Experimental method Easy signal selection with + at rest qe = 180° e + + Detector outline • Stopped beam of >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 nfac 03 -N. Y. June 6 th 2003 9

MEG Signal and background signal e accidental enn correlated e + + e nn n qe = 180° Ee = E = 52. 8 Me. V e + + n Te = T nfac 03 -N. Y. June 6 th 2003 e nn ee e. Z n n e + + 10

MEG Required Performances The sensitivity is limited by the accidental background The 3 10 -14 allows BR ( e ) 10 -13 but needs FWHM Exp. /Lab Year DEe/Ee (%) DE /E (%) Dte (ns) Dqe (mrad) Stop rate (s-1) Duty cyc. (%) BR (90% CL) SIN 1977 8. 7 9. 3 1. 4 - 5 x 105 100 3. 6 x 10 -9 TRIUMF 1977 10 8. 7 6. 7 - 2 x 105 100 1 x 10 -9 LANL 1979 8. 8 8 1. 9 37 2. 4 x 105 6. 4 1. 7 x 10 -10 Crystal Box 1986 8 8 1. 3 87 4 x 105 (6. . 9) 4. 9 x 10 -11 MEGA 1999 1. 2 4. 5 1. 6 17 2. 5 x 108 (6. . 7) 1. 2 x 10 -11 MEG 2007 0. 8 4 0. 15 19 2. 5 x 107 100 1 x 10 -13 nfac 03 -N. Y. June 6 th 2003 11

MEG Detector Construction Switzerland Russia Drift Chambers Beam Line DAQ LXe Tests Purification Italy Japan e+ counter Trigger LXe Calorimeter nfac 03 -N. Y. June 6 th 2003 LXe Calorimeter, Magnetic spectrometer 12

MEG The PSI p. E 5 beam Primary proton beam nfac 03 -N. Y. June 6 th 2003 13

MEG Beam studies Optimization of the beam elements: • Wien filter for /e separation • Solenoid to couple beam and spectrometer • Degrader to reduce the momentum for a 150 m target Intermediate results: • • U-version Z-version R (total) 1. 3*108 +/s R (after W. filter) 7. 3*107 +/s 9. 5*107 +/s R (after solenoid) V 6. 5 mm, H 5. 5 mm to be studied /e separation 11 7 Measurements on Z-branch are going on in 2003 Design of the transport solenoid is started nfac 03 -N. Y. June 6 th 2003 14

MEG COBRA spectrometer COnstant Bending RAdius (COBRA) spectrometer • Constant bending radius independent of emission angles Gradient field Uniform field • High p. T positrons quickly swept out Gradient field nfac 03 -N. Y. June 6 th 2003 Uniform field 15

MEG Gradient field nfac 03 -N. Y. June 6 th 2003 16

MEG The solenoids • Bc = 1. 26 T current = 359 A • Five coils with three different diameters • “Crash” Tests completed • Compensation coils to suppress the stray field around the LXe detector • High-strength aluminum stabilized superconductor • Winding completed @TOSHIBA thin magnet (1. 46 cm Aluminum, 0. 2 X 0) nfac 03 -N. Y. June 6 th 2003 • Ready to be shipped at PSI during summer 17 OK

MEG Positron Tracker • 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 (X, Y) ~200 m (drift time) (Z) ~ 300 m (charge division vernier strips) nfac 03 -N. Y. June 6 th 2003 18

MEG Drift chambers R&D (1) 90 Sr source Tokyo Univ. OK (no magnetic field full prototype test at PSI by the end of this year) nfac 03 -N. Y. June 6 th 2003 19

MEG Drift chambers R&D (2) • Full scale test in November • Improved vernier strips structure (more uniform resolution) FWHM • Summary of Drift Chamber simulation nfac 03 -N. Y. June 6 th 2003 20

MEG (90% C. L. ) as a function of longitudinal position resolution nfac 03 -N. Y. June 6 th 2003 21

MEG Positron Timing Counter BC 404 • Two layers of scintillator read by PMTs placed at right angles with each other Outer: timing measurement Inner: additional trigger information • Goal time~ 40 psec (100 ps FWHM) nfac 03 -N. Y. June 6 th 2003 22

MEG Timing Counter R&D CORTES: Timing counter test facility with cosmic rays • Scintillator bar (5 cm x 100 cm long) • Telescope of 8 x MSGC • Measured resolutions time~60 psec independent of incident position • time improves as ~1/√Npe 2 cm thick nfac 03 -N. Y. June 6 th 2003 23

MEG Liquid Xe calorimeter • • • 800 l of Liquid Xe ~800 PMT immersed in LXe Only scintillation light High luminosity Unsegmented volume Refrigerator H. V. Signals Cooling pipe Experimental check Vacuum for thermal insulation Liq. Xe Al Honeycomb window PMT Plasticfiller 1. 5 m nfac 03 -N. Y. June 6 th 2003 24

MEG LXe performance • Complete MC simulations • At labs the resolution is dominated by photostatistics FWHM(E)/E 2. 5% (including edge effects) FWHM(E)/E (%) Energy resolution strongly depends on optical properties of LXe • At labs Ldet limits from shower fluctuations + detector response need of reconstruction algorithms FWHM(E)/E 4% nfac 03 -N. Y. June 6 th 2003 25

MEG Xenon Calorimeter Prototype The Large Prototype (LP) • 40 x 50 cm 3 • 228 PMTs, 100 litres Lxe (the largest in the World) • Purpose • Test cryogenic operation on a long term and on a large volume • Measure the Lxe properties • Check the reconstruction methods • Measure the Energy, Position and Timing resolutions with: • • Cosmic rays -sources 60 Me. V eˉ from KSR storage ring 40 Me. V from TERAS Compton Backscattering • e+ and 50 Me. V from p° at PSI nfac 03 -N. Y. June 6 th 2003 Planned in this year 26

MEG The LP -sources LEDs nfac 03 -N. Y. June 6 th 2003 27

MEG LP: LXe optical properties • First tests showed that the number of scintillation photons was MUCH LESS than expected • It improved with Xe cleaning: Oxysorb + gas getter + re-circulation (took time) • There were a strong absorption due to contaminants (mainly H 2 O) March 2002 Present. . . labs> 1 m nfac 03 -N. Y. June 6 th 2003 28

MEG LP: Radioactive background • -trigger with 5 106 gain • Geometrical cuts to exclude sources 40 K (1. 461 Me. V) • Energy scale: -source • 208 Tl • 40 K (2. 59± 0. 06) Me. V 208 Tl (2. 614 Me. V) (1. 42 ± 0. 06) Me. V • uniform on the front face • few 10 min (with non-dedicated trigger) • nice calibration for low energy ’s Seen for the first time! Studies are going on: spatial distribution of background inside the detector nfac 03 -N. Y. June 6 th 2003 29

MEG Timing resolution test t = ( z 2 + sc 2)1/2 = (802 + 602)1/2 ps = 100 ps (FWHM) our goal z Time-jitter due to photon interaction point sc Scintillation time and photon statistics Measurement of sc 2 with 60 Me. V electron beam • weighted average of the PMT TDCs time-walk corrected • sc vs ph. el. 52. 8 Me. V peak • extrapolation at 52. 8 Mev is ok • new PMT with QE 5 25% nfac 03 -N. Y. June 6 th 2003 30 5% 10% 15%QE

MEG Cryostat (PMT test facility) nfac 03 -N. Y. June 6 th 2003 31

MEG nfac 03 -N. Y. June 6 th 2003 32

MEG Trigger Electronics LXe inner face (312 PMT) • Built on a FADC-FPGA architecture 3 Type 1 LXe lateral faces (488 PMT: 4 to 1 fan-in) . . • Positron- coincidence in time and direction 16 20 boards 20 x 48 . • energy . . . • Uses easily quantities: 16 3 Type 1 10 boards 1 board e+ hit point in timing counter v time correlation – e+ v angular correlation – e+ nfac 03 -N. Y. June 6 th 2003 200 s-1 20 s-1 33 3 Type 1 1 board 12 x 48 2 boards . . . g interaction point (PMT of max charge) 16 4 x 48 10 x 48 12 boards v Beam rate 108 s-1 v Fast LXe energy sum > 45 Me. V 2 103 s-1 Type 2 • More complex algorithms implementable Timing counters (160 PMT) 2 boards Type 2 2 x 48 2 VME 6 U 1 VME 9 U • Design and simulation of type 1 board completed • Prototype board delivered by late spring

MEG Readout electronics • 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 nfac 03 -N. Y. June 6 th 2003 34 Prototypes delivered in autumn

MEG Sensitivity Summary Detector parameters Cuts at 1, 4 FWHM Signal Single Event Sensitivity 4 10 -14 2 10 -14 Backgrounds 3 10 -15 Upper Limit at 90% CL BR ( e ) 1 10 -13 Discovery 4 events (P = 2 10 -3) correspond nfac 03 -N. Y. June 6 th 2003 35 BR = 2 10 -13

MEG Summary and Time Scale • This experiment may provide a clean indication of New Physics • Measurements and detector simulation make us confident that we can reach the SES of 4 x 10 -14 to e (BR 10 -13) • Final prototypes will be measured within this year • Large Prototype for energy, position and timing resolutions of s • Full scale Drift Chamber • -Transport and degrader-target • Financed this year in Italy+Switzerland • Tentative time profile Lo. I Proposal Planning 1998 1999 2000 Revised document now Assembly R&D 2001 2003 2004 2005 2006 2007 http: //meg. psi. ch http: //meg. pi. infn. it http: //meg. icepp. s. u-tokyo. ac. jp More details at nfac 03 -N. Y. June 6 th 2003 2002 Data Taking 36