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Muon Physics at the Front End of a n Factory An introduction

Muon Physics at the Front End of a n Factory An introduction. B. Lee Roberts Boston University with some theory projections taken from Yasuhiro Okada KEK. roberts @ bu.edu http://physics.bu.edu/roberts/html. Outline. Introduction to the muon G F Lepton Flavor Violation

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Muon Physics at the Front End of a n Factory An introduction

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  1. Muon Physics at the Front End of a n FactoryAn introduction B. Lee Roberts Boston University with some theory projections taken from Yasuhiro Okada KEK roberts @ bu.edu http://physics.bu.edu/roberts/html B. Lee Roberts ISS Plenary Meeting: RAL 26 April 2006

  2. Outline • Introduction to the muon • GF • Lepton Flavor Violation • Magnetic and electric dipole moments • Summary and conclusions. B. Lee Roberts ISS Plenary Meeting: RAL 26 April 2006

  3. The Muon (“Who ordered that?”) • Lifetime ~2.2 ms, practically forever • 2nd generation lepton • mm/me = 206.768 277(24) • produced polarized • in-flight decay: both “forward” and “backward” muons qre highly polarized • Paul Scherrer Institut has 108m/s in a beam B. Lee Roberts ISS Plenary Meeting: RAL 26 April 2006

  4. What can we learn from the m’s death? • The strength of the weak interaction • i.e. the Fermi constant GF • The fundamental nature of the low-energy weak interaction • i.e. is it scalar, vector, tensor, pseudo-scalar, pseudo-vector or pseudo-tensor? B. Lee Roberts ISS Plenary Meeting: RAL 26 April 2006

  5. Predictive power in weak sector of SM. Difference between the charged current and neutral current propagators The radiative correction shown above depends on mt2. Comparisons of charged, vrs. neutral currents gives information on mt. tm helped predict the mass of the top quark B. Lee Roberts ISS Plenary Meeting: RAL 26 April 2006

  6. The Electro-Weak Working Group Fits: • Predicted • Input: GF(17 ppm), • (4 ppb at q2=0), • MZ (23 ppm), • Measured: from GF The mLan experiment at PSI will accumulate 1012m-decays and measure GF to ~1 ppm. If LHC provides a Higgs Mass, then the precision of the confrontation with the SM will greatly improve B. Lee Roberts ISS Plenary Meeting: RAL 26 April 2006

  7. Lepton Flavor Violation The standard-model gauge bosons do not permit leptons to mix, but new physics at the TeV scale such as SUSY does. The Muon Trio: LFV, MDM, EDM B. Lee Roberts ISS Plenary Meeting: RAL 26 April 2006

  8. @ Mplanck GUT Yukawa interaction Neutrino Yukawa interaction CKM matrix Neutrino oscillation SUSY GUT and SUSY Seesaw model L.J.Hall,V.Kostelecky,S.Raby,1986;A.Masiero, F.Borzumati, 1986 The flavor off-diagonal terms in the slepton mass matrix are induced by renormalization effects due to GUT and/or neutrino interactions. LFV B. Lee Roberts ISS Plenary Meeting: RAL 26 April 2006

  9. Many models beyond the S-M contain sources of LFV • Although the simple seesaw or Dirac neutrino model predicts too small generate branching ratios for the charged lepton LFV, other models of neutrino mass generation can induce observable effects. • For example: • Generalized Zee model (K.Hasagawa, C.S.Lim, K.Ogure, 2003) • Neutrino mass from the warped extra dimension (R.Kitano,2000) • R-parity violating SUSY model (A.de Gouvea,S.Lola,K.Tobe,2001) • Triplet Higgs model (E.J.Chun, K.Y.Lee,S.C.Park; N.Kakizaki,Y.Ogura, F.Shima, 2003) • Left-right symmetric model (V.Cirigliano, A.Kurylov, M.J.Ramsey-Musolf, P.Vogel, 2004) • SUSY seesaw model (F.Borzumati and A.Masiero 1986) B. Lee Roberts ISS Plenary Meeting: RAL 26 April 2006

  10. Experimental bounds (Ti) m → econversion search at the level of 10-18 is proposed in the future muon facility at J-PARC (PRIME). B. Lee Roberts ISS Plenary Meeting: RAL 26 April 2006

  11. m+e-→m-e+ Branching Ratio Limit Past and Future of LFV Limits B. Lee Roberts ISS Plenary Meeting: RAL 26 April 2006

  12. m → e g branching ratio (typical example) SUSY seesaw model J.Hisano and D.Nomura,2000 SU(5) and SO(10) SUSY GUT K.Okumura MEGA SO(10) SU(5) Right-handed selectron mass The branching ratio can be large in particular for SO(10) SUSY GUT model. Right-handed neutrino mass B. Lee Roberts ISS Plenary Meeting: RAL 26 April 2006

  13. Comparison of three processes If the photon penguin process dominates, there are simple relations among these branching ratios. This is true in many, but not all SUSY modes. B. Lee Roberts ISS Plenary Meeting: RAL 26 April 2006

  14. Comparison of three muon processes in various new physics models want to measure all three LFV processes to disentangle the models B. Lee Roberts ISS Plenary Meeting: RAL 26 April 2006

  15. The First -N  e-N Experiment Steinberger and Wolf • After the discovery of the muon, it was realized it could decay into an electron and a photon or convert to an electron in the field of a nucleus. • Without any flavor conservation, the expected branching fraction for +e+ is about 10-5. • Steinberger and Wolf first looked for -N  e-N, publishing a null result in 1955, Re < 2  10-4 Absorbs e- from - decay 9” Conversion e- reach this counter B. Lee Roberts ISS Plenary Meeting: RAL 26 April 2006

  16. Z dependence of mu-e conversion branching ratio R.Kitano, M.Koike and Y.Okada. 2002 have calculated the coherent mu-e conversion branching ratios in various nuclei for general LFV interactions to see: (1) which nucleus is the most sensitive to mu-e conversion searches, (2) whether one can distinguish various theoretical models by the Z dependence. Relevant quark level interactions Dipole Scalar Vector B. Lee Roberts ISS Plenary Meeting: RAL 26 April 2006

  17. dipole scalar vector providing another way to discriminate different models m-e conversion rate normalized to Al The branching ratio is largest for the atomic number of Z=30 – 60. For light nuclei, Z dependences are similar for different operator forms. Sizable difference of Z dependences for dipole, scalar and vector interactions. This is due to a relativistic effect of the muon wave function. Kitano, Koike, Okada B. Lee Roberts ISS Plenary Meeting: RAL 26 April 2006

  18. Muon MDM (g-2) chiral changing Muon EDM The Muon Trio: MDM, EDM B. Lee Roberts ISS Plenary Meeting: RAL 26 April 2006

  19. Electric and Magnetic Dipole Moments Transformation properties: An EDM implies both PandT are violated. An EDM at a measureable level would imply non-standard model CP. The baryon/antibaryon asymmetry in the universe, needs new sources of CP. B. Lee Roberts ISS Plenary Meeting: RAL 26 April 2006

  20. m→ e MDM, EDM ~ ~ SUSY connection between am , Dμ , μ→ e B. Lee Roberts ISS Plenary Meeting: RAL 26 April 2006

  21. Magnetic Dipole moments • Field invented by Otto Stern in 1921 B. Lee Roberts ISS Plenary Meeting: RAL 26 April 2006

  22. (in modern language) B. Lee Roberts ISS Plenary Meeting: RAL 26 April 2006

  23. Dirac + Pauli moment B. Lee Roberts ISS Plenary Meeting: RAL 26 April 2006

  24. Non-Standard Model Value for Muon (g-2) ? S ? e vrs. m : relative contributionof heavier things B. Lee Roberts ISS Plenary Meeting: RAL 26 April 2006

  25. aμ is sensitive to a wide range of new physics • substructure • SUSY (with large tanβ ) • many other things (extra dimensions, etc.) B. Lee Roberts ISS Plenary Meeting: RAL 26 April 2006

  26. The hadronic contribution to am has to come from data B. Lee Roberts ISS Plenary Meeting: RAL 26 April 2006

  27. world average E821 achieved 0.5 ppm and the e+e- based theory is also at the 0.6 ppm level. Both can be improved. All E821 results were obtained with a “blind” analysis. B. Lee Roberts ISS Plenary Meeting: RAL 26 April 2006

  28. Based on the latest report on e+e- → hadrons there is an apparent discrepancy at the level of 2.9 s . . . • A new experiment at BNL (E969) could improve the confrontation with theory by a factor of 2 • What implications might the possible (g-2) discrepancy have for muon physics at a neutrino factory? • New physics at the TeV scale? • Could one do 10 times better? • A few words about the technique which is important to understand for the EDM experiment B. Lee Roberts ISS Plenary Meeting: RAL 26 April 2006

  29. We measure the difference frequency between the spin and momentum precession With an electric quadrupole field for vertical focusing 0 B. Lee Roberts ISS Plenary Meeting: RAL 26 April 2006

  30. Muon lifetime tm = 64.4 ms (g-2) period ta = 4.37 ms Cyclotron period tC = 149 ns Scraping time (E821) 7 to 15 ms Total counting time ~700 ms Total number of turns ~4000 The 700 ton (g-2)m precision storage ring B. Lee Roberts ISS Plenary Meeting: RAL 26 April 2006

  31. The magnetic field is measured and controlled using pulsed NMR, and the muon spin precession is measured using m→e n n decay B. Lee Roberts ISS Plenary Meeting: RAL 26 April 2006

  32. (g-2) ten times better (0.05 ppm) ? • Need to know to 0.01 ppm (10 ppb) • Need ~1014 polarized muons at ≥ 3 GeV/c momentum • Need substantial improvements in theory for the result to be interpreted B. Lee Roberts ISS Plenary Meeting: RAL 26 April 2006

  33. Present EDM Limits *projected B. Lee Roberts ISS Plenary Meeting: RAL 26 April 2006

  34. Naïve scaling would imply that but in some models the dependence is greater, e.g. B. Lee Roberts ISS Plenary Meeting: RAL 26 April 2006

  35. Model Calculations of m EDM μ EDM may be enhanced above mμ/me× e EDM Magnitude increases with magnitude of ν Yukawa couplings and tan β μEDM greatly enhancedwhen heavy neutrinos non-degenerate B. Lee Roberts ISS Plenary Meeting: RAL 26 April 2006

  36. aμ implications for the muon EDM B. Lee Roberts ISS Plenary Meeting: RAL 26 April 2006

  37. Spin Frequencies: m in B field with MDM & EDM 0 spin difference frequency = ws - wc The motional E - field, β X B, is much stronger than laboratory electric fields. The EDM causes the spin to precess out of plane. B. Lee Roberts ISS Plenary Meeting: RAL 26 April 2006

  38. Dedicated EDM Experiment 0 Use a radial E-field to turn off the wa precession With wa = 0, the EDM causes the spin to steadily precess out of the plane. wh B. Lee Roberts ISS Plenary Meeting: RAL 26 April 2006

  39. In the next talk, Klaus Jungmann will give a few more details on a dedicated muon EDM experiment. B. Lee Roberts ISS Plenary Meeting: RAL 26 April 2006

  40. Summary and Conclusions • There are a number of interesting topics which can be pursued at a high intensity muon source • Lepton Flavor Violation • Search for a permanent EDM of the muon are the most compelling • The next talk will cover these topics in more detail B. Lee Roberts ISS Plenary Meeting: RAL 26 April 2006

  41. Extra Projections B. Lee Roberts ISS Plenary Meeting: RAL 26 April 2006

  42. The error budget for E969 represents a continuation of improvements already made during E821 • Field improvements:better trolley calibrations, better tracking of the field with time, temperature stability of room, improvements in the hardware • Precession improvementswill involve new scraping scheme, lower thresholds, more complete digitization periods, better energy calibration B. Lee Roberts ISS Plenary Meeting: RAL 26 April 2006

  43. B. Lee Roberts ISS Plenary Meeting: RAL 26 April 2006

  44. B. Lee Roberts ISS Plenary Meeting: RAL 26 April 2006

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