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Muon Physics at the Front-end of a Neutrino Factory

Muon Physics at the Front-end of a Neutrino Factory. First published muon observation: Paul Kunze, Z. Phys. 83, 1 (1933). “a particle of uncertain nature”. Lee Roberts Department of Physics Boston University. roberts @bu.edu http://g2pc1.bu.edu/~roberts. TexPoint fonts used in EMF.

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Muon Physics at the Front-end of a Neutrino Factory

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  1. Muon Physics at the Front-end of a Neutrino Factory First published muon observation: Paul Kunze, Z. Phys. 83, 1 (1933) “a particle of uncertain nature” Lee Roberts Department of Physics Boston University roberts @bu.edu http://g2pc1.bu.edu/~roberts B. Lee Roberts, NuFact2008 – 4 July 2008 TexPoint fonts used in EMF. Read the TexPoint manual before you delete this box.: AAA

  2. m B. Lee Roberts, NuFact2008 – 4 July 2008

  3. Outline • Introduction to the muon • The Muon Trio: • The Magnetic dipole moment: am , • The Electric Dipole Moment dm • Lepton Flavor Violation • Other Muon Experiments • Summary and conclusions. Some slides/figures have been borrowed from: Klaus Jungmann, Dave Hertzog, Klaus Kirch Jim Miller, Yasuhiro Okada and Andries van der Schaaf B. Lee Roberts, NuFact2008 – 4 July 2008

  4. Muon properties: • Born Polarized • Decay is self-analyzing High-energy e± carry muon spin information! B. Lee Roberts, NuFact2008 – 4 July 2008

  5. What has the muon done for us (besides being associated with the production of or ) ? • The strength of the weak interaction • i.e. the Fermi constant GF(more properly Gm) • The V - A nature of the weak interaction • Lepton flavor conservation in m-decay (thus far) • VEV of the Higgs field: • Induced form-factors in nuclear m-capture • complementary to b-decay • Constraints on new physics from am, • constrains many models of new physics B. Lee Roberts, NuFact2008 – 4 July 2008

  6. Theory of Magnetic and Electric Dipole Moments Proc. R. Soc. (London) A117, 610 (1928) B. Lee Roberts, NuFact2008 – 4 July 2008

  7. Magnetic and Electric Dipole Moments B. Lee Roberts, NuFact2008 – 4 July 2008

  8. For leptons, radiative corrections dominate the value of a≃ 0.00116… The magnetic dipole moment directed along spin. Dirac Theory: gs = 2 Dirac + Pauli moment Bottom line: Anomalous moment represents a sum rule over all physics, not just the known physics. B. Lee Roberts, NuFact2008 – 4 July 2008

  9. Muon Magnetic Dipole Momoment am Muon EDM Modern Notation: chiral changing B. Lee Roberts, NuFact2008 – 4 July 2008

  10. The SM Value for the muon anomaly (10-10) 10 (2) New BaBar e+e- → p p results expected in September Eduardo de Rafael:Theory of the muon anomalousmagnetic momentP and T violation at low energies, Heidelberg, Jun - 2008 11 659 178.3 (4.8) # from Miller, de Rafael, Roberts, Rep. Prog. Phys. 70 (2007) 795–881 B. Lee Roberts, NuFact2008 – 4 July 2008

  11. aμ is sensitive to a wide range of new physics • e.g. SUSY (with large tanβ ) • many other things (extra dimensions, etc.) B. Lee Roberts, NuFact2008 – 4 July 2008

  12. Spin Motion in a Magnetic Field 0 wC - cyclotron frequency wS - spin frequency wa - spin turns relative to the momentum B. Lee Roberts, NuFact2008 – 4 July 2008

  13. Figure of merit: (MDM or EDM) As spin precesses, the number of high E electrons oscillates with frequency wa. Count number of e- with Ethresh ≥ 1.8 GeV B. Lee Roberts, NuFact2008 – 4 July 2008

  14. We count high-energy electrons as a function of time. B. Lee Roberts, NuFact2008 – 4 July 2008

  15. E821 achieved 0.5 ppm and the e+e- based theory is also at the 0.6 ppm level. Difference is 3.4s 3.7s MdRR=Miller, de Rafael, Roberts, Rep. Prog. Phys. 70 (2007) 795 B. Lee Roberts, NuFact2008 – 4 July 2008

  16. Expt The Snowmass Points and Slopes give benchmarks to test observables with model predictionsMuon g-2 is a powerful discriminator ...no matter where the final value lands! Present Future? Model Version B. Lee Roberts, NuFact2008 – 4 July 2008

  17. Complementary to LHC data: e.g.am provides the best measure of m and tanb MSSM reference point SPS1a With these SUSY parameters, LHC gets tan b of 10.22 ± 9.1. See: arXiv:0705.4617v1 [hep-ph] with improvements in theory and experiment things can improve to: m > 0 by > 6 s tan b to < 20% B. Lee Roberts, NuFact2008 – 4 July 2008

  18. The search for a Muon Electric Dipole Moment B. Lee Roberts, NuFact2008 – 4 July 2008

  19. Purcell and Ramsey: EDM would violate ParityProposed to search for an EDM of the neutron “raises directly the question of parity.” Phys. Rev. 78 (1950) B. Lee Roberts, NuFact2008 – 4 July 2008

  20. If CPT is valid, an EDM would imply non-standard model CP. Electric Dipole Moment: P T Transformation Properties B. Lee Roberts, NuFact2008 – 4 July 2008

  21. The present EDM limits are orders of magnitude from the standard-model value The discovery of a permanent EDM would change our picture of nature at least as profoundly as the discovery of neutrino mass has! B. Lee Roberts, NuFact2008 – 4 July 2008

  22. e EDM (e.cm) Excluded region (Tl atomic beam) Commins (2002) MSSM f ~ 1 Multi Higgs de < 1.6 x 10-27 e.cm Left -Right E. Hinds’ e-EDM experiment at Imperial College with YbF molecules is starting to explore this region MSSM f ~ a/p Standard Model 10-22 10-24 n 10-26 199Hg 10-28 10-30 The SUSY CP problem! 10-32 The strong CP problem! 10-34 10-36 with thanks to Ed Hinds B. Lee Roberts, NuFact2008 – 4 July 2008

  23. aμ(new physics) implications for dm Either dµ is of order 10–22 e cm, or the CP phase is strongly suppressed! B. Lee Roberts, NuFact2008 – 4 July 2008

  24. Model Calculations of m EDM μ EDM may be enhanced above mμ/me× e EDM Magnitude increases with magnitude of n Yukawa couplings and tan β μ EDM greatly enhanced when heavy neutrinos non-degenerate B. Lee Roberts, NuFact2008 – 4 July 2008

  25. Spin Frequencies: m in B field with MDM & EDM 0 The motional E - field, β X B, is (~GV/m). The EDM causes the spin to precess out of plane. B. Lee Roberts, NuFact2008 – 4 July 2008

  26. Plane of the spin precession tipped by the angle d Number above (+) and below (-) the midplane will vary as: Total frequency w wa wh B. Lee Roberts, NuFact2008 – 4 July 2008

  27. E821 looked for this vertical oscillation in 3 ways • No significant oscillation was found • The observed Dam is not from an EDM at the 2.2 s level • One can improve significantly at a neutrino factory, since an EDM limit of 10-23e·cm needs NP 2 = 1016 Bottom line: Muon EDM measurement needs the high intensity that could be available at a neutrino factory. Also need modified technique! *Coming soon to a preprint server near you B. Lee Roberts, NuFact2008 – 4 July 2008

  28. 0 Dedicated EDM Experiment Use a radial E-field to turn off the wa precession “Frozen spin” With wa = 0, the EDM causes the spin to steadily precess out of the plane. wh B. Lee Roberts, NuFact2008 – 4 July 2008

  29. “Frozen spin” technique to measure EDM • Turn off the (g-2) precession with radial E • Up-Down detectors measure EDM asymmetry • Look for an up-down asymmetry building up with time • Side detectors measure (g-2) precession • To prove the spin is frozen B. Lee Roberts, NuFact2008 – 4 July 2008

  30. PSI suggestion: Adelmann and Kirchhep-ex/0606034 A. Adelmann1, K. Kirch1, C.J.G. Onderwater2, T. Schietinger1, A. Streun1 1PSI, 2KVI (by A. Streun) B. Lee Roberts, NuFact2008 – 4 July 2008

  31. ? new (g-2) NuFact Muon EDM Limits: Present and Future E821: G. Bennett, et al., (Muon g-2 collaboration) to be submitted to PRD 2008 E821 Need: NA2 = 1016 for dm≃ 10-23e·cm B. Lee Roberts, NuFact2008 – 4 July 2008

  32. SUSY slepton mixing m→ e MDM, EDM ~ ~ SUSY connection between MDM, EDM and the lepton flavor violating transition momentm → e B. Lee Roberts, NuFact2008 – 4 July 2008

  33. 10-1 10-3 10-5 10-7 10-9 10-11 10-13 m+ e-→m -e+ Branching Ratio Limit 1940 1950 1960 1970 1980 1990 2000 Lepton Flavor Violation 2-body final state mono-energetic electron B. Lee Roberts, NuFact2008 – 4 July 2008

  34. Experimental bounds (Ti) Under some assumptions the DLf = 1 rates are related B. Lee Roberts, NuFact2008 – 4 July 2008

  35. Presently active: m +→ e+g (MEG @ PSI) • First running is going on now • goal < 10-13 B. Lee Roberts, NuFact2008 – 4 July 2008

  36. 1s Balmer series 2p 2s Lyman series r Muonic Atom: m- bound in hydrogen-like atomic orbit coherent process B. Lee Roberts, NuFact2008 – 4 July 2008

  37. me - conversion operators have calculated the coherent m-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. R.Kitano, M.Koike and Y.Okada. 2002 Relevant quark level interactions Dipole Scalar Vector B. Lee Roberts, NuFact2008 – 4 July 2008

  38. 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 similar for different operators Sizable difference of Z dependences for dipole, scalar and vectorinteractions (relativistic effect of Ym). Kitano, Koike, Okada Bottom line: If you can observe muon-electron conversion, a study of the Z dependence might help sort out which operators contribute. dipole scalar vector providing another way to discriminate different models B. Lee Roberts, NuFact2008 – 4 July 2008

  39. 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 lepton flavor conservation, the expected branching fraction for +  e+ is about 10-5 • Steinberger and Wolf m-N  e-N, (1955) Re< 2  10-4 Absorbs e- from - decay 9” Conversion e- reach this counter B. Lee Roberts, NuFact2008 – 4 July 2008

  40. SINDRUM II @PSI Data and simulation (simulated) signal decay in orbit Two New Proposals for m to e Conversion Experiments • m2e at Fermilab • based on MECO / MELC proposals • COMET at J-PARC -to be upgraded to PRISM/PRIME prompts suppressed B. Lee Roberts, NuFact2008 – 4 July 2008

  41. Proton Target Target Shielding (Copper) Pions Protons enter here B=5T Target Shielding (Tungsten) Muons B=2.5T The m2e Apparatus proposed for Fermilab Phase 1: 90% C.L. limit of Rme< 6 x 10-17 Phase 2: 90% C.L. limit of Rme ≲ 10-18 Superconducting Transport Solenoid (2.5 T – 2.1 T) p beam Crystal Calorimeter Straw Tracker Superconducting Production Solenoid (5.0 T – 2.5 T) Collimators Superconducting Detector Solenoid (2.0 T – 1.0 T) Muon Stopping Target B. Lee Roberts, NuFact2008 – 4 July 2008

  42. COMET Proposal @ J-PARC me conversion 90% CLRme < 10-16 curved detector to reduce low E DIO background B. Lee Roberts, NuFact2008 – 4 July 2008

  43. Rme < 10-18 Bottom line: FFAG reduces Dp of the muon beam by phase rotation: narrow Dt → narrow Dp⇒ thinner stopping target better e- resolution and eliminates the pions which can cause ZN (p -,g) background! B. Lee Roberts, NuFact2008 – 4 July 2008

  44. Predicted M-M Conversion 1957- Named System “Muonium” ? Muonium to Anti-muonium Conversion Flavor oscillations well established in quark sector L. Willmann, et al., PRL 82, 49 (1999) B. Lee Roberts, NuFact2008 – 4 July 2008

  45. L. Willmann, et al., PRL 82, 49 (1999) (done @PSI) 90% CL: B. Lee Roberts, NuFact2008 – 4 July 2008

  46. Future Efforts at Existing Facilities • (g-2)m • FNAL ? • J-PARC ? • MEG • running now! • m2e • proposal being prepared for Fermilab • COMET/ PRISM/PRIME • proposed to J-PARC, future under discussion Bottom line: The ultimate sensitivity for me conversion could be reached at the front end of a neutrino factory. The discovery of LFV would also significantly change our view of the world. B. Lee Roberts, NuFact2008 – 4 July 2008

  47. Summary • Muon physics has provided much information in the development of the standard model, including a hint of new physics in am. • The electric dipole moment could be measured to a competitive level (to e-) at a neutrino factory. • Muon flavor violation can be pursued to the ultimate sensitivity, or studied systematically at a neutrino factory. • The observation of either of these SM “forbidden” effects would be incredibly important in reshaping our view of nature. B. Lee Roberts, NuFact2008 – 4 July 2008

  48. Extra Projections B. Lee Roberts, NuFact2008 – 4 July 2008

  49. 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, NuFact2008 – 4 July 2008

  50. PSI suggestion: A. Adelmann1, K. Kirch1, C.J.G. Onderwater2, T. Schietinger1, A. Streun1 B = 1 T pm = 125 MeV/c bm = 0.77, gm = 1.57 P ≈ 0.9 E = 0.64 MV/m R = 0.35 m hep-ex/0606034 In 1 year of running @ PSI B. Lee Roberts, NuFact2008 – 4 July 2008

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