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Muon (g-2)

Muon (g-2). Status and Plans for the Future. B. Lee Roberts Department of Physics Boston University. roberts@bu.edu http://physics.bu.edu/roberts.html. Magnetic moments, g-factors. Lepton Flavor Violation Muon MDM (g-2) chiral changing Muon EDM. The Muon Trio:. Dirac,.

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Muon (g-2)

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  1. Muon (g-2) Status and Plans for the Future B. Lee Roberts Department of Physics Boston University roberts@bu.edu http://physics.bu.edu/roberts.html B. Lee Roberts, PANIC05, Santa Fe,27 October, 2005

  2. Magnetic moments, g-factors B. Lee Roberts, PANIC05, Santa Fe,27 October, 2005

  3. Lepton Flavor Violation Muon MDM (g-2) chiral changing Muon EDM The Muon Trio: Dirac, Pauli moment B. Lee Roberts, PANIC05, Santa Fe,27 October, 2005

  4. 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, PANIC05, Santa Fe,27 October, 2005

  5. Present EDM Limits final limit will be better, * projected. B. Lee Roberts, PANIC05, Santa Fe,27 October, 2005

  6. Unlike the EDM, there is a large SM value for the MDM The Electron: to the level of the experimental error (4ppb), Contribution of μ, (or anything heavier than the electron) is ≤4 ppb. For the muon, the relative contribution of heavier particles B. Lee Roberts, PANIC05, Santa Fe,27 October, 2005

  7. Standard Model Value for (g-2) B. Lee Roberts, PANIC05, Santa Fe,27 October, 2005

  8. SM value dominated by hadronic issues: • Lowest order hadronic contribution ( ~ 60 ppm) • Hadronic light-by-light contribution ( ~ 1 ppm) The error on these two contributions will ultimately limit the interpretation of a more precise muon (g-2) measurement. B. Lee Roberts, PANIC05, Santa Fe,27 October, 2005

  9. Lowest Order Hadronic contribution from e+e- annihilation B. Lee Roberts, PANIC05, Santa Fe,27 October, 2005

  10. a(had) from hadronic t decay? • Assume: CVC, no 2nd-class currents, isospin breaking corrections. • n.b. t decay has no isoscalar piece, while e+e- does • Many inconsistencies in comparison of e+e- and t decay: - Using CVC to predict t branching ratios gives 0.7 to 3.6 s discrepancies with reality. - Fpfrom t decayhas different shape from e+e-. B. Lee Roberts, PANIC05, Santa Fe,27 October, 2005

  11. New Physics; SUSY (with large tanβ ) B. Lee Roberts, PANIC05, Santa Fe,27 October, 2005

  12. SUSY connection between am , dμ , μ→ e B. Lee Roberts, PANIC05, Santa Fe,27 October, 2005

  13. Muon (g-2) : E821 • Superconducting “superferric” storage ring • superconducting inflector • fast muon kicker • magic g, • direct muon injection with a fast non-ferric kicker B. Lee Roberts, PANIC05, Santa Fe,27 October, 2005

  14. Use an E field for vertical focusing 0 spin difference frequency = ws - wc B. Lee Roberts, PANIC05, Santa Fe,27 October, 2005

  15. Spin Precession Frequencies: m in B field with both an MDM and EDM The motional E - field, β X B, is much stronger (~GV/m) than laboratory electric fields. B. Lee Roberts, PANIC05, Santa Fe,27 October, 2005

  16. Spin Precession Frequencies: m in B field with both an MDM and EDM The motional E - field, β X B, is much stronger (~GV/m) than laboratory electric fields. The EDM causes the spin to precess out of plane and increases |w| B. Lee Roberts, PANIC05, Santa Fe,27 October, 2005

  17. Spin Precession Frequencies: m in B field with both an MDM and EDM The if the EDM were 2.8 x 10-18 e cm, wa would increase by 2.9 ppm. B. Lee Roberts, PANIC05, Santa Fe,27 October, 2005

  18. Muon (g-2): Store m ± in a storage ring magnetic field averaged over azumuth in the storage ring B. Lee Roberts, PANIC05, Santa Fe,27 October, 2005

  19. Muon (g-2) Present precision: ± 0.5 ppm B. Lee Roberts, PANIC05, Santa Fe,27 October, 2005

  20. Can we improve the sensitivity of this confrontation between experiment and theory? • Yes • E969 at BNL has scientific approval to go from 0.5 ppm → 0.2ppm • At a more intense muon facility we could do better. Will Theory Improve beyond 0.6 ppm? • Yes • better R measurements from: KLOE, BaBar, Belle, SND and CMD2 at Novosibirsk • More work on the strong interaction • Theory could eventually improve to ~0.2 ppm B. Lee Roberts, PANIC05, Santa Fe,27 October, 2005

  21. Exclusion/Limitations on New Physics B. Lee Roberts, PANIC05, Santa Fe,27 October, 2005

  22. SUSY, dark matter, (g-2) DE821 CMSSM (constrained minimal supersymmetric model) scalar mass gaugino mass B. Lee Roberts, PANIC05, Santa Fe,27 October, 2005

  23. Future Comparison: DE969 = Dnow B. Lee Roberts, PANIC05, Santa Fe,27 October, 2005

  24. Future Comparison: DE969= 0 Historically (g-2) has played an important role in restricting models of new physics. B. Lee Roberts, PANIC05, Santa Fe,27 October, 2005

  25. E969 at BNL • Scientific approval in September 2004 • at present: no funds for construction or running • Goal: total error = 0.2 ppm • lower systematic errors • more beam B. Lee Roberts, PANIC05, Santa Fe,27 October, 2005

  26. Strategy of the improved experiment • More muons – E821 was statistics limited sstat = 0.46 ppm, ssyst = 0.3 ppm • Backward-decay, higher-transmission beamline • Double the quadrupoles in the p decay line B. Lee Roberts, PANIC05, Santa Fe,27 October, 2005

  27. Strategy of the improved experiment • New, open-end inflector • Upgrade detectors, electronics, DAQ x 2 in flux B. Lee Roberts, PANIC05, Santa Fe,27 October, 2005

  28. E969: Systematic Error Goal B. Lee Roberts, PANIC05, Santa Fe,27 October, 2005

  29. aμ implications for the muon EDM This paper, published before our February 2001 announcement predicts a large muon EDM, and a corresponding SUSY contribution to aμ comparable to what we might be observing, with the e- EDM predicted to be 0.1 of the present limit. B. Lee Roberts, PANIC05, Santa Fe,27 October, 2005

  30. aμ implications for the muon EDM B. Lee Roberts, PANIC05, Santa Fe,27 October, 2005

  31. Dedicated EDM measurement: • operate withg ≈ 5 << 29.3 • use a radial E-field to turn off (g-2) precession • Place detectors above and below the vacuum chamber and look for an up/down asymmetry which builds up with time B. Lee Roberts, PANIC05, Santa Fe,27 October, 2005

  32. Beam Needs: NP2 = 5*10-7 • the figure of merit is Nμ times the polarization. We need to reach the 10-24 e-cm level. • Since SUSY calculations range from 10-22 to 10-32 e cm, more muons is better. (Up+Down) (Up-Down) time (ms) B. Lee Roberts, PANIC05, Santa Fe,27 October, 2005

  33. Where E821 came from: B. Lee Roberts, PANIC05, Santa Fe,27 October, 2005

  34. Today: All E821 results were obtained with a “blind” analysis. world average B. Lee Roberts, PANIC05, Santa Fe,27 October, 2005

  35. Summary • (g-2)m provides a precise check of the standard model, and accesses new physics in a way complementary to other probes. • (g-2)m provides serious constraints on physics beyond the standard model. • The hadronic contribution will eventually set the limit on useful precision, but substantial improvement can and will be made, both in theory and experiment beyond the present situation. B. Lee Roberts, PANIC05, Santa Fe,27 October, 2005

  36. B. Lee Roberts, PANIC05, Santa Fe,27 October, 2005

  37. Recent News from Novosibirsk • SND has just released their results (hep-ex/0506076) for the cross section e+e- → p +p - over the r. • Error on dispersion integral 50% higher than CMD2 • Good agreement with CMD2 • Completely independent from CMD2 B. Lee Roberts, PANIC05, Santa Fe,27 October, 2005

  38. Improved transmission into the ring Inflectoraperture Inflector Storage ring aperture E821 Closed End P969 Proposed Open End B. Lee Roberts, PANIC05, Santa Fe,27 October, 2005

  39. Beyond E969? • It’s not clear how far we can push the present technique. • To get to 0.06 ppm presents many challenges. • Perhaps a new storage ring design, and a smaller aperture. • detectors for another factor of 4 will be very challenging. • At a proton driver/neutrino factory we certainly we can get more muons B. Lee Roberts, PANIC05, Santa Fe,27 October, 2005

  40. E969: Systematic Error Goal • Field improvements will involve better trolley calibrations, better tracking of the field with time, temperature stability of room, improvements in the hardware • Precession improvements will involve new scraping scheme, lower thresholds, more complete digitization periods, better energy calibration B. Lee Roberts, PANIC05, Santa Fe,27 October, 2005

  41. Evaluating the Dispersion Integral Agreement between Data (BES) and pQCD (within correlated systematic errors) use data Better agreement between exclusive and inclusive (2) data than in 1997-1998 analyses use QCD use QCD from A. Höcker ICHEP04 B. Lee Roberts, PANIC05, Santa Fe,27 October, 2005

  42. Tests of CVC (A. Höcker – ICHEP04) B. Lee Roberts, PANIC05, Santa Fe,27 October, 2005

  43. Shape of Fp from e+e- and hadronic t decay Comparison between t data and e+e- data from CDM2 (Novosibirsk) zoom New precision data from KLOE confirms CMD2 B. Lee Roberts, PANIC05, Santa Fe,27 October, 2005

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