1. Dec. 8th, 2000NOON 20001 A new   e  experiment at PSI For the MUEGAMMA collaboration Stefan Ritt (Paul Scherrer Institute, Switzerland) Introduction Experimental Technique Current status

2. Dec. 8th, 2000NOON 20002 Physics Motivation SUSY theories generically predict LFV LFV forbidden by Standard Model Processes like  +  e +  are not “contaminated” by SM processes and therefore very clean Discovered oscillations are expected to enhance LFV rate The search for  +  e +  is therefore a promising field to find physics beyond the SM

3. Dec. 8th, 2000NOON 20003 Prediction from SUSY SU(5) This experiment Current experimental bound 2) f t (M)=2.4  >0 M l =50GeV 1) 1)J. Hisano et al., Phys. Lett. B391 (1997) 341 2)MEGA collaboration, hep-ex/9905013

4. Dec. 8th, 2000NOON 20004 Connection with oscillations 1) 1)J. Hisano and D. Nomura, Phys. Rev. D59 (1999) 116005 2)MEGA collaboration, hep-ex/9905013 2) This experiment

5. Dec. 8th, 2000NOON 20005 Previous  +  e +  Experiments PlaceYearUpper limitAuthor SIN (PSI), Switzerland1977 < 1.0  10 -9 A. Van der Schaaf et al. TRIUMF, Canada1977 < 3.6  10 -9 P. Depommier et al. LANL, USA1979 < 1.7  10 -10 W.W. Kinnison et al. LANL, USA1986 < 4.9  10 -11 R.D. Bolton et al. LANL, USA1999 < 1.2  10 -11 MEGA Collab., M.L. Brooks et al. New experiment: 10 -14 at PSI Letter of Intend 1998 Proposal 1999, approved May 1999 New experiment: 10 -14 at PSI Letter of Intend 1998 Proposal 1999, approved May 1999

6. Dec. 8th, 2000NOON 20006 MEG Collaboration InstituteCountryMain Resp.HeadScientistsStudents ICEPP, Univ. of TokyoJapanLXe CalorimeterT. Mori122 Waseda UniversityJapanCryogenicsT. Doke52 INFN, PisaItaly e + counter, trigger, M.C. C. Bemporad43 IPNS, KEK, TsukubaJapan Supercoducting Solenoid A. Maki5- PSISwitzerland Drift Chamber, Beamline, DAQ S. Ritt4- BINP, NovosibirskRussia LXe Tests and Purification B. Khazin4- Nagoya UniversityJapanCryogenicsK. Masuda1- 35 7

7. Dec. 8th, 2000NOON 20007 Experimental Method Stopped  beam of 10 8 s -1, 100% duty factor Liquid Xe calorimeter for  detection Solenoidal magnetic spectrometer with gradient field Radial drift chambers for e + momentum determination Timing counter for e + Stopped  beam of 10 8 s -1, 100% duty factor Liquid Xe calorimeter for  detection Solenoidal magnetic spectrometer with gradient field Radial drift chambers for e + momentum determination Timing counter for e + E e = 52.8 MeV Kinematics  e  = 180° E g = 52.8 MeV e  

8. Dec. 8th, 2000NOON 20008 Signal and Background  +  e +  signal very clear –E  = E e+ = 52.8 MeV –   e+ = 180° –e + and  in time Background –Radiative  + decays –Accidental overlap Detector Requirements –Excellent energy resolution –Excellent timing resolution –Good angular resolution ee e  e   ee  e    e  e 

9. Dec. 8th, 2000NOON 20009   e  Signature  e  E e,E  = 52.8MeV  e  E e,E  < 52.8MeV X = E e /52.8MeV Y = E  /52.8MeV

10. Dec. 8th, 2000NOON 200010 Sensitivity and Background Rate BR(  e  ) = (N  T  /4   e    sel ) -1 = 0.94  10 -14 NN 1  10 8 T 2.2  10 7 s (~50 weeks)  /4  0.09 ee 0.95  0.7  sel 0.8 FWHM EeEe 0.7% EE 1.4%  e  12 mrad tete 150 ps Prompt Background B pr  10 -17 Accidental BackgroundB acc   E e  t e  (  E  ) 2 (  e  ) 2  5  10 -15

11. Dec. 8th, 2000NOON 200011 Paul Scherrer Institute Experimental Hall

12. Dec. 8th, 2000NOON 200012 Experimental Hall

13. Dec. 8th, 2000NOON 200013 Sindrum II @ PSI  - Ti  e - Ti : Oct. 2000 (50d) beam time: 90% C.L. limit: 6.1 10 -13 B ue =4 10 -12

14. Dec. 8th, 2000NOON 200014  E5 Beam Line 10 8  /s on 5  5 mm 2 Neutron background measured in 1998 Beam test planned in Spring 2001 10 8  /s on 5  5 mm 2 Neutron background measured in 1998 Beam test planned in Spring 2001

15. Dec. 8th, 2000NOON 200015 Detector

16. Dec. 8th, 2000NOON 200016 LXe Calorimeter ~800l liquid Xe (3t) ~800 PMTs immersed in LXe Only scintillation light detected Fast response (45 ns decay time) High light output (70% of NaI(Tl)) 1) High uniformity compared with segmented calorimeters High channel occupancy will be accommodated by special trigger scheme ~800l liquid Xe (3t) ~800 PMTs immersed in LXe Only scintillation light detected Fast response (45 ns decay time) High light output (70% of NaI(Tl)) 1) High uniformity compared with segmented calorimeters High channel occupancy will be accommodated by special trigger scheme 1) T. Doke and K. Masuda, NIM A 420 (1999) 62

17. Dec. 8th, 2000NOON 200017  Response Signal is distributed over many PMTs in most cases Weighted mean of PMTs on the front face   x ~ 4mm FWHM Broadness of distribution   z ~ 16mm FWHM Timing resolution   t ~ 100ps FWHM Energy resolution ~ 1.4% FWHM depends on light attenuation in LXe Signal is distributed over many PMTs in most cases Weighted mean of PMTs on the front face   x ~ 4mm FWHM Broadness of distribution   z ~ 16mm FWHM Timing resolution   t ~ 100ps FWHM Energy resolution ~ 1.4% FWHM depends on light attenuation in LXe x z

18. Dec. 8th, 2000NOON 200018 Calorimeter Prototypes 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 “Small”“Large” 264 PMTs, 150 l LXe Assembly finished next January Measure resolutions with 40 MeV photon beam at ETL, Tsukuba, Japan

19. Dec. 8th, 2000NOON 200019 Positron Spectrometer Homogeneous Field Gradient Field (COnstant-Bending-RAdius) e + from  +  e +  Ultra-Thin (~3g/cm2) superconducting solenoid with 1.2 T field Ultra-Thin (~3g/cm2) superconducting solenoid with 1.2 T field

20. Dec. 8th, 2000NOON 200020 Drift Chamber 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 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

21. Dec. 8th, 2000NOON 200021 Prototype Test at PSI 0, 0.6, 0.8, 1T field 3 tilting angles Data analysis finished soon 0, 0.6, 0.8, 1T field 3 tilting angles Data analysis finished soon

22. Dec. 8th, 2000NOON 200022 Positron timing counter Aimed resolution ~100ps FWHM Beam tests at KEK in July 1999 Taken over by Pisa group Scintillators ordered Beam tests next spring Aimed resolution ~100ps FWHM Beam tests at KEK in July 1999 Taken over by Pisa group Scintillators ordered Beam tests next spring

23. Dec. 8th, 2000NOON 200023 Trigger Requirements  Beam rate10 8 s -1  Fast LXe energy sum > 45MeV2  10 3 s -1   interaction point  e + hit point in timing counter  time correlation  – e + 200 s -1  angular corrlation  – e + 20 s -1  Beam rate10 8 s -1  Fast LXe energy sum > 45MeV2  10 3 s -1   interaction point  e + hit point in timing counter  time correlation  – e + 200 s -1  angular corrlation  – e + 20 s -1 E e = 52.8 MeV Kinematics  e  = 180° E g = 52.8 MeV e   M.C.

24. Dec. 8th, 2000NOON 200024 Trigger Implementation FADC 100MHz 8-bit FPGA FADC SRAM Trigger FADC FPGA FADC SRAM BS    Max...... T[ns] 0 50 60 70..150 160 170 >45MeV   e+ AND 10 stages = 1024 chn … 800 channels - Baseline Subtraction...

25. Dec. 8th, 2000NOON 200025 Waveform Digitizing Waveform Digitizing for all channels Custom domino sampling chip (DSC) designed at PSI Costs per DSC ~1US$ 2.5 GHz sampling speed  40ps timing resolution Sampling depth 1024 bins  400ns (100ns+300ns) Readout electronics similar to trigger Drift chamber signals go directly to FADC (100MHz) Waveform Digitizing for all channels Custom domino sampling chip (DSC) designed at PSI Costs per DSC ~1US$ 2.5 GHz sampling speed  40ps timing resolution Sampling depth 1024 bins  400ns (100ns+300ns) Readout electronics similar to trigger Drift chamber signals go directly to FADC (100MHz) FPGA FADCSRAM... Analog Waveform Sampling Chip (DSC) 2.5GHz 40MHz, 10 bit VME Previous Version 1.2 GHz C. Brönnimann et al., NIM A420 (1999) 264

26. Dec. 8th, 2000NOON 200026 Time Table 199719981999200020012002 2003 2004 2005 PlanningR & DAssemblyData Taking now Conclusions Preparations are going well in all areas of the experiment Innovative technologies developed useful for other experiments Next major milestone: Large prototype test in Tsukuba spring 2001 Increasing support from PSI and Pisa New collaborators are welcome Preparations are going well in all areas of the experiment Innovative technologies developed useful for other experiments Next major milestone: Large prototype test in Tsukuba spring 2001 Increasing support from PSI and Pisa New collaborators are welcome http://meg.icepp.s.u-tokyo.ac.jp http://meg.pi.infn.it http://meg.psi.ch http://meg.icepp.s.u-tokyo.ac.jp http://meg.pi.infn.it http://meg.psi.ch