Lepton Flavour Violation

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1 Lepton Flavour Violation Search for e at Paul Scherrer Institut Satoshi Mihara ICEPP, Univ. of Tokyo icepp.s..s.u-tokyo.ac.jp, psi.ch,

2 Contents Introduction MEG experiment at PSI detectors Sensitivity, Background estimation Summary

3 Lepton Flavour Violation

4 Physics Motivation SUSY Finite slepton mixing appears through radiative corrections Experimental Bound Experimental Bound This experiment This experiment SUSY-GUT predicts an even larger value Hisano, Moroi, Tobe, and Yamaguchi PLB391(1997)341

5 Neutrino Oscillation and g-2g Neutrino Oscillation Anomalous muon magnetic moment 1) J.Hisano and D. Nomura, Phys. Rev. D59 (1999) ) MEGA collaboration, hep-ex/ Br( e

6 Chronorogy of e Search 1937 Discovery of the mesotron in cosmic rays 1947 Two meson hypothesis e 1957 e predicted at 10-4 two neutrinos e 1967 Lepton number conservation generally accepted 1977 rumored at 10-8 level B.R. limit < 2x10-10 at LAMPF 1987 Crystal Box results < 5x MEGA data taking 1999 MEGA result < 1.2x May at PSI Proposal Place SIN (PSI), Switzerland TRIUMF, Canada LANL, USA LANL, USA LANL, USA Year Upper limit < < < < < Author A. Van der Schaaf et al. P. Depommier et al. W.W. Kinnison et al. R.D. Bolton et al. MEGA Collab., M.L. Brooks et al.

7 Previous experiments searching Pulse beam of 2.5x10 8 /sec with a duty factor of 6%. 1.2x10 14 muons stopped Superconducting solenoidal magnet and low material MWPC. Photon detector with Pb converters. All the signal were treated as degitial data at the detector level. Best limit on Br( e ) of 1.2x for LFV I(MEGA)

8 Previous experiments searching for LFV II (SINDRUM II) B ue=4 ue = Br( N en) ) = 1/( )x Br( e ) depends on the target material

9 What we learned from the MEGA experiment Use DC beam Achieve better measurement Energy, Position and Time Prepare better tracking environment

10 Where we should search for e?

11 Paul Scherrer Institut Experimental Hall

12 Accelerator facilities at PSI

13 The ring cyclotron Nominal operation current mA Max > 2.0mA

14 and fluxes at E5 Surface muon bem p target N t

15 MEG collaboration Institute ICEPP, Univ. of Tokyo Country Japan Main Resp. LXe Calorimeter Head T. Mori Scientists 12 Students 3 Waseda University Japan Cryogenics T. Doke 5 3 INFN, Pisa IPNS, KEK, Tsukuba PSI BINP, Novosibirsk Nagoya University Italy Japan Switzerland Russia Japan e + counter, trigger, M.C. Supercoductin g Solenoid Drift Chamber, Beamline, DAQ LXe Tests and Purification Cryogenics C. Bemporad A. Maki S. Ritt B. Khazin K. Masuda

16 MEG experiment overview PSI E5 beam line Liquid Xe Photon detector COBRA (Constant Bending Radius) spectrometer Plan to start DAQ in summer 2003 e Kinematics θ eγ = 180 µ E e = 52.8 MeV E g = 52.8 MeV γ

17 E5 beam line Cleaning-Stage to reduce positron contamination in the beam Beam line study started in summer 2001 Measure Phase space of surface muon beam -spot-sizesize divergences stopping-rate momentum Measure & optimize positron contamination in the beam optimal initial beam momentum vs µ + /e + -ratio Secondary Beam- Blocker Primary Beam-BlackerBlacker Cleaning Stage Transport solenoid or Separator

18 The photon detector Detect scintillation light from Liq. Xe Fast response, Good Energy, and Position resolutions Mini-Kamiokande type NaI: : too slow CsI,, BGO: poor resolution at 52.8MeV Inhomoginity to cover large area

19 Liquid xenon properties Atomic Number 54 Atomic Weight Boiling point 165K Liquid density 3.0kg/cm 3 W ph value (for 1MeV electrons) 24 ev Decay time constants f (fast component) s (slow component) r (recombination) 4.2nsec 22nsec 45nsec Peak wavelength of scintillation light 174nm

20 Small prototype of the liquid Small 32 PMTs, 2.3 l LXe Tested with radioactive sources 51 Cr, 137 Cs, 54 Mn, 88 Y Extrapolated resolutions at 52.8 MeV in agreement with quoted numbers xenon detector

21 Large Prototype Large 264 PMTs, 110 l LXe Assembly finished Measure resolutions with 40 MeV photon beam at ETL, Tsukuba, Japan

22 COBRA spectrometer Sweep out curling positrons rapidly. Constant bending radius independent of the emission angles.

23 Superconducting solenoid Bc = 1.26T B z=1.25m =1.25m = 0.49T Peak field in the coil 1.72T Operating current 359A Load line ratio ~ 5.2K Construction has been started

24 Positron tracker 16 radial chambers with 20 wires each Staggered cells measure both position and time He C 2 H 6 gas to reduce multiple scattering Vernier pattern to determine z coordinate

25 Positron tracker mini prototype 0, 0, 0.6, 0.6, 0.8, 0.8, 1T 11T T field field 3 tilting angles

26 Positron timing counter e + (t ϕ)r Impact Point (t z ) R (t ϕ) L δ = 0 e + σ = 65 ps (t ) z L e + ϕ z 1m δ = 48.5º Aimed resolution ~100ps FWHM Beam tests at at KEK KEK in in July July 1999 Cosmic ray ray test test at at CORTES facility σ = 55 ps

27 Trigger Trigger and DAQ Back to Back positron & gamma and timing coincidence γ e + Beam Beam rate rate s -1-1 Fast Fast LXe LXe energy energy sum sum > 45MeV 45MeV s -1-1 γγinteraction point point e + + hit hit point point in in timing timing counter time time correlation γ γ e s -1-1 angular corrlation γ γ e s -1-1 DAQ DAQ All signals are digitized by 2.5GHz wave form digitizers

Slow control system MSCB (http://midas midas.psi.

small experiments "poor man's" version with less flexibility

28 Slow control system MSCB ( midas.psi.ch) The usage of field buses are usually not suitable for small experiments "poor man's" version with less flexibility but optimized for experiment environments and much cheaper (typical 20US$ per node).

29 Sensitivity Sensitivity N µ =1x10 8 /sec, 2.2x10 7 sec running W/4π=0.09, =0.09,ε e =0.95, ε γ =0.7, and ε sel =0.8 Single Event sensitivity :0.94x10-14 Y = E γ /52.8MeV Y µ Decays in Acceptance X = E e /52.8MeV X

30 Background Main background sources Radiative + decay Accidental overlap NOT back to back, NOT in time e e e + Can be reduced down to level e?

31 Beam line Current Status Beam line study has been started this summer Photon detector Large Prototype test in progress design work of the xenon vessel is starting Superconducting solenoid Coil winding is starting Cryostat construction next year

32 Current Status cont d Positron tracker R&D using the prototype Mechanical design of the support system in progress Positron timing counter Prototype study almost completed Test in magnetic field will start soon Electronics be ready in 2002 now Planning R & D Assembly Data Taking

33 Summary R&D simulation

Kenji Ozone (ICEPP, Univ. of Tokyo, Japan) Outline. Introduction prototype R&D ー PMTs ー small & large type summary

Liquid Xe detector for m + e + g search Kenji Ozone (ICEPP, Univ. of Tokyo, Japan) Outline Introduction prototype R&D ー PMTs ー small & large type summary Three Talks XENON01 LXe detector for m eg search