1. Muon Rare Decay at PRISM Masaharu Aoki Osaka University KEKNP01 December 10-12, 2001, KEK

2. Dec 10-12, 2002KEKNP01, M. Aoki2 Outline Introduction –LFV –What is PRISM |  L i |=1 Processes –  -e Conversion in nuclei |  L i |=2 Processes – Muonium-antimuonium conversion The recent experiment Activation method at PRISM –      Conversion Theoretical background Conceptual design Concluding Remarks

3. Dec 10-12, 2002KEKNP01, M. Aoki3 LFV with low-energy muons

4. Dec 10-12, 2002KEKNP01, M. Aoki4 PRISM (=Phase Rotation Intense Slow Muon source) not in scale

5. Dec 10-12, 2002KEKNP01, M. Aoki5 PRISM Features Higher muon intensity –10 11 -10 12  - /sec Pulsed beam (>100 Hz) –background rejection Narrow energy spread (±0.5-1.0 MeV) –thinner muon-stopping target better e - resolution and acceptance point source Low momentum muon (=68 MeV/c) –Less scattering backgrounds Less beam contamination –no pion contamination long flight path at FFAG (150 m) –beam extinction between pulses kicker magnet at FFAG entrance –pure charge state

6. Dec 10-12, 2002KEKNP01, M. Aoki6        -e Conversion in nuclei

7. Dec 10-12, 2002KEKNP01, M. Aoki7 Flavor Physics flavor mixing –nondiagonal elements of the mass matrices quark lepton (neutrino) slepton squark normal particles SUSY particles ex. K-decays, B-decays ex. neutrino oscillation ex. charged lepton LFV sensitive to slepton mixing

8. Dec 10-12, 2002KEKNP01, M. Aoki8 SU(5) SUSY-GUT prediction SO(10) SUSY-GUT prediction –enhanced by (m  /m  ) 2 (=100) from SU(5) prediction SUSY-GUT Prediction goal f t (M)=2.4  M 1 =50 GeV f t (M)=2.4  M 1 =50 GeV

9. Dec 10-12, 2002KEKNP01, M. Aoki9 SUSY with RH Majorana neutrino a la Nomura and Hisano

10. Dec 10-12, 2002KEKNP01, M. Aoki10 PRIME  PRIsm Muon-Electron conversion experiment –PRIME and MECO

11. Dec 10-12, 2002KEKNP01, M. Aoki11 Muon Decay in Orbit Muon decay in orbit (  (E  e -E e ) 5 ) – E e > 103.9 MeV –  E e = 350 keV – N BG ~ 0.17 @ R=10 -18 present limit MECO goal PRIME goal signal

12. Dec 10-12, 2002KEKNP01, M. Aoki12 Momentum Resolution Momentum resolution simulation 100 keV sigma (240 keV FWHM) 25  200  m Al 750 keV FWHM @MECO 20  50  m Ti

13. Dec 10-12, 2002KEKNP01, M. Aoki13 Muon Stopping Target Simulation for Ti 65 MeV/c 2% width –Correlation to momentum Ti target of 1 mm thickness Will stop 80 % of the netgativemuons ! Ten times better than MECO. Further improvement of Momentum spread will improve more.

14. Dec 10-12, 2002KEKNP01, M. Aoki14 Event Displays Event 1 Event 2 target

15. Dec 10-12, 2002KEKNP01, M. Aoki15 Backgrounds (1) Radiative  capture N BG <0.1(@R=10 -16 )  decay in flight N BG <10 -4 (@R=10 -16 ) –Long flight length (150m) 30 m FFAG circumference  5 turns –Double kicker injection at the FFAG entrance Low momentum (~68 MeV/c) –Additional extinction by the kicker << 10 -4 –Absolutely no pions Sweep out all pions

16. Dec 10-12, 2002KEKNP01, M. Aoki16 Radiative muon capture N BG <0.01(@R=10 -16 ) –Endpoint energy for Ti = 89.7 MeV Signal = 104.3 MeV –Better e - net momentum resolution Thin muon stopping targets Beam electrons and muon decay in flight N BG <0.02(@R=10 -16 ) N BG <0.007(@R=10 -16 ) –Kinematically not allowed E e = 68 ± 2 MeV/c < 103.9 MeV E  = 68± 2 MeV/c < 77 MeV/c Cosmic ray N BG <0.004(@R=10 -16 ) –<1 MHz (low duty factor) Less beam contamination, less junk trigger Anti-proton –Absorber at the FFAG entrance Backgrounds (2)

17. Dec 10-12, 2002KEKNP01, M. Aoki17 PRIME Rate Issue 10 4 ~10 5 times larger than that in MECO MECO : 1 MHz PRIME : 100 Hz Spiral Solenoid Spectrometer Space separation –Large Acceptance (>41%) –Large DIO Rejection (>10 9 ) low detector rate (<10 per pulse) Electron Accumulator RING (EARING) Time separation –Electron storage ring –Slow extraction to a detector

18. Dec 10-12, 2002KEKNP01, M. Aoki18 Spiral Solenoid Spectrometer a la Sasao

19. Dec 10-12, 2002KEKNP01, M. Aoki19      2 Muonium-antimuonium conversion and  -  Conversion in nuclei

20. Dec 10-12, 2002KEKNP01, M. Aoki20 Muonium-Antimuonium Conversion Doubly charged Higgs boson Heavy Majorana neutrinos A neutral scalar SUSY Bilepton

21. Dec 10-12, 2002KEKNP01, M. Aoki21 Mu-AntiMu: PSI Experiment

22. Dec 10-12, 2002KEKNP01, M. Aoki22 Mu-AntiMu: Activation Method(1) No active devices Requirements –Absolutely no  - contamination –No pion contamination TRIUMF –T.M. Huber, et al. Phys. Rev. D 41 (1990) 2709-2725

23. Dec 10-12, 2002KEKNP01, M. Aoki23 Mu-AntiMu: Activation Method(2) Sensitivity –Small, but could be improved by more than an order of magnitude T.M. Huber, et al. Phys. Rev. D 41 (1990) 2709-2725

24. Dec 10-12, 2002KEKNP01, M. Aoki24 Mu-AntiMu: Activation Method(3) Mu-Antimu with PRISM

25. Dec 10-12, 2002KEKNP01, M. Aoki25   -   Conversion muonic atom (1s state) –nuclear muon capture  - + (A,Z)    –muon decay in orbit  -  e   –Exotic processes |  L i | = 1 –  - + (A,Z)  e   –  - + (A,Z)  e   |  L i | = 2 –  - + (A,Z)    Experimental status –Direct measurement → NOT EXIST –Indirect measurement → Kaon decay BR(K +        ) < 3.0  10 -9 –Which corresponds to BR(   A   A ) < 10 -12 –L.S. Littenberg and R. Shrock, PLB 491(2000)285-290

26. Dec 10-12, 2002KEKNP01, M. Aoki26   -   Conv. : Physics(1) J.H.Missimer, R.N. Mohapatra and N.C. Mukhopadhyay, PRD50(1994)2067-2070 For examples R 5 = 10 -18  muonic version of  decay   -diagonal of    A  e + A conversion

27. Dec 10-12, 2002KEKNP01, M. Aoki27   -   Conv. : Physics(2) E. Takasugi(Osaka Univ.) –neutrino oscillation |M| ~ double beta decay BR ~ 10 -41

28. Dec 10-12, 2002KEKNP01, M. Aoki28   -   Conv.: Choice of Target  - + (A,Z)    –T = M(Z,A) - M(Z,A-2) - 2m e - E  (1S) > 0 No candidate from stable isotopes 44 Ti(  -,  + ) 44 Ca   ( 44 Ti) = 47 years 72 Se(  -,  + ) 72 Ge   ( 44 Se) = 8.4days 82 Sr(  -,  + ) 82 Kr   ( 44 Sr) = 25days –J.H.Missimer, R.N. Mohapatra and N.C. Mukhopadhyay, PRD50(1994)2067-2070 44 Ti(  -,  + ) 44 Ca –M(Z,A) - M(Z,A-2) = 3.92 MeV –E  (1S) = 1.28 MeV –T = 1.62 MeV p  = 18.5 MeV/c  = 0.17

29. Dec 10-12, 2002KEKNP01, M. Aoki29   -   Conv.: Production of Target Natural abundance = ZERO !! Production process : 45 Sc(p,2n) 44 Ti – 45 Sc =100% –Production cross section Maximum @ E p = 30 MeV  max  = 63 mb Yield –Target Material : Sc –Target volume : 0.5 cm 3 –Proton beam : 50 MeV, 10mA Upstream section of JHF linac (DTL) –10 days of irradiation 0.3% of whole Sc material could be transformed to 44 Ti

30. Dec 10-12, 2002KEKNP01, M. Aoki30   -   Conv.: Signal and Backgrounds Radioactive Target –> 100 Ci / g Very low energy  + emision –T = 1.62 MeV Very small final state phase space factor –Small energy –Large Coulomb distortion Fermi function, F = 0.028 –Relative phase space factor to (  ,e + ) is only 4.8  10 -3 Opposite charged final state –  - + (A,Z)    Huge amount of backgrounds –Radiation from 44 Sc –Muon decay orbit 44 Ti(  -,  + ) 44 Ca

31. Dec 10-12, 2002KEKNP01, M. Aoki31   -   Conv.: How to detect Catching  +  e   –E e = 0 ~ 52 MeV –Enormous amount of background from e +  - + (A,Z)    –R(radiative capture / capture) = 10 -4 –Target thickness 50  m »R = 10 -7 direct measurement of  + –T = 1.68 MeV Very low energy muon Target thickness should be < a few 100  m High Brightness High Intensity Muon Beam –Separation of e +- is necessary

32. Dec 10-12, 2002KEKNP01, M. Aoki32   -   Conv.: Conceptual Design Surface Muon Beam Channel

33. Dec 10-12, 2002KEKNP01, M. Aoki33   -   Conv.: Sensitivity  - Beam from PRISM –10 12 /sec –  p/p = ±2.0 % Target –50  m Sc0.015 g/cm 2 Muon stopping fraction = 4% – 44 Ti concentration 0.3% 0.3% of   would be trapped in 44 Ti  + acceptance (0.4%) –Beam line acceptance 50 msr –  p/p = 10% Beam Time –1 nominal year10 7 sec R < 2  10 -13

34. Dec 10-12, 2002KEKNP01, M. Aoki34   -   Conv.: Comparison with K   A  e  A –BR < 1.7  10 -12 PSI BR(K +      e  ) < 10 -11 –BR(K +      e  ) < 5.0  10 -10 BNL-E865 –BR(   A  e  A) < 10 -16 BNL-MECO K +    e    e  –BR < 6.4  10 -10 BNL-E865 –0 2  decay |  j U ei 2  j | < 0.4 eV –“Many orders of magnitude less than Kaon data” K +       –BR < 3.0  10 -9 BNL-E865 Which corresponds to BR(   A   A ) < 10 -12 –BR < 10 -12 FNAL-CKM Which corresponds to BR(   A   A ) < 5  10 -16 L.S. Littenberg and R. Shrock, PLB 491(2000)285-290

35. Dec 10-12, 2002KEKNP01, M. Aoki35 Concluding Remarks PRISM –PRISM will provide a high-intensity high-quality muon beam for vaious rare muon decay experiments. It is mainly designed for  -e conversion experiment, but can also provide good opportunity to the |  L i |=2 physics.  -e Conversion –BR(  A -> eA ) ~ 10 -18 Mu-AntiMu –G Mu-AntiMu < 10 -4 G F  - -  + conversion –R < 2  