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Muon (g-2): Past, Present and Future

Muon (g-2): Past, Present and Future. B. Lee Roberts On behalf of the E969 Collaboration. roberts @ bu.edu http://physics.bu.edu/roberts/html. (in modern language) (and in English). Dirac + Pauli moment. Schwinger term. s m = 1 / 2. g m = 2.

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Muon (g-2): Past, Present and Future

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  1. Muon (g-2): Past, Present and Future B. Lee Roberts On behalf of the E969 Collaboration roberts @ bu.edu http://physics.bu.edu/roberts/html B. Lee Roberts, Dipole Moments In Storage Rings AGS/RHIC Workshop,7 June 2006

  2. (in modern language) (and in English) B. Lee Roberts, Dipole Moments In Storage Rings AGS/RHIC Workshop,7 June 2006

  3. Dirac + Pauli moment Schwinger term B. Lee Roberts, Dipole Moments In Storage Rings AGS/RHIC Workshop,7 June 2006

  4. sm = 1/2 gm = 2 B. Lee Roberts, Dipole Moments In Storage Rings AGS/RHIC Workshop,7 June 2006

  5. B. Lee Roberts, Dipole Moments In Storage Rings AGS/RHIC Workshop,7 June 2006

  6. B. Lee Roberts, Dipole Moments In Storage Rings AGS/RHIC Workshop,7 June 2006

  7. Standard Model Value Muon for (g-2) S ? e vrs. m : relative contributionof heavier things B. Lee Roberts, Dipole Moments In Storage Rings AGS/RHIC Workshop,7 June 2006

  8. The hadronic contribution to am comes from e+e-→hadrons B. Lee Roberts, Dipole Moments In Storage Rings AGS/RHIC Workshop,7 June 2006

  9. Measurements and Sensitivity of am B. Lee Roberts, Dipole Moments In Storage Rings AGS/RHIC Workshop,7 June 2006

  10. When we started in 1983, theory and experiment were known to about 10 ppm. Theory uncertainty was ~ 9 ppm Experimental uncertainty was 7.3 ppm B. Lee Roberts, Dipole Moments In Storage Rings AGS/RHIC Workshop,7 June 2006

  11. world average E821 achieved 0.54 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, Dipole Moments In Storage Rings AGS/RHIC Workshop,7 June 2006

  12. With an apparent discrepancy at the level of 2.9 s . . . it’s interesting and you have to work harder to improve the measurement and the theory value …. B. Lee Roberts, Dipole Moments In Storage Rings AGS/RHIC Workshop,7 June 2006

  13. BNL E969 Collaboration R.M. Carey, I. Logashenko, K.R. Lynch, J.P. Miller, B.L. Roberts Boston University G. Bunce, W. Meng, W. Morse, P. Pile, Y.K. Semertzidis Brookhaven National Laboratory D. Grigoriev, B.I. Khazin, S.I. Redin, Y. M. Shatunov, E. Solodov Budker Institute of Nuclear Physics F.E. Gray, B. Lauss, E.P. Sichtermann UC Berkeley and LBL Y. Orlov – Cornell University J. Crnkovic, P. Debevec, D.W. Hertzog, P. Kammel, S. Knaack, R. McNabb University of Illinois at Urbana-Champaign K.L. Giovanetti – James Madison University K.P. Jungmann, C.J.G. Onderwater – KVI Groningen T.P. Gorringe, W. Korsch U. Kentucky P. Cushman – University ofMinnesota M. Aoki, Y. Arimoto, Y. Kuno, A. Sato, K. Yamada Osaka University S. Dhawan, F.J.M. Farley – Yale University This group contains the core of E821, and we will build on our strength and experience there. B. Lee Roberts, Dipole Moments In Storage Rings AGS/RHIC Workshop,7 June 2006

  14. We measure the difference frequency between the spin and momentum precession With an electric quadrupole field for vertical focusing 0 B. Lee Roberts, Dipole Moments In Storage Rings AGS/RHIC Workshop,7 June 2006

  15. Experimental Technique Central orbit Kicker Modules R=711.2cm d=9cm Electric Quadrupoles Protons Pions Inflector (from AGS) p=3.1GeV/c Target (1.45T) Injection orbit • Muon polarization • Muon storage ring • injection & kicking • focus by Electric Quadrupoles • 24 electron calorimeters Storage ring B. Lee Roberts, Dipole Moments In Storage Rings AGS/RHIC Workshop,7 June 2006

  16. Pedestal vs. Time We base E969 on a modified version of this proven concept. E821 used a “forward” decay beam, with pp 1.7% above pmagic to provide a separation at K3/K4 Pions @ 3.115 GeV/c Decay muons @ 3.094 GeV/c Our models show that by quadrupling the quads and going further above pmagic the flash is decreased and the muon flux will grow by approximately 2-3 Near side Far side B. Lee Roberts, Dipole Moments In Storage Rings AGS/RHIC Workshop,7 June 2006

  17. The Production Target top view of target proton beam B. Lee Roberts, Dipole Moments In Storage Rings AGS/RHIC Workshop,7 June 2006

  18. Decay Channel Plenty of room to add more quadrupoles to increase the acceptance of the beamline. B. Lee Roberts, Dipole Moments In Storage Rings AGS/RHIC Workshop,7 June 2006

  19. The incident beam must enter through the magnet yoke and through an inflector magnet B. Lee Roberts, Dipole Moments In Storage Rings AGS/RHIC Workshop,7 June 2006

  20. Upper Pole Piece Space limitations prevent matching the inflector exit to the storage aperture B. Lee Roberts, Dipole Moments In Storage Rings AGS/RHIC Workshop,7 June 2006

  21. The E821 inflector magnet had closed ends which lost half the beam. Length = 1.7 m Central field = 1.45 T Open end prototype, built and tested →X2 Increase in Beam B. Lee Roberts, Dipole Moments In Storage Rings AGS/RHIC Workshop,7 June 2006

  22. E969 needs 5 times the muon flux that E821 stored. • Open inflector x 2 • Quadruple the quadrupoles x 2 – 3 Beam increase design factor x 4 – 6 At 3% above pmagic the reduced injection flash will permit us to begin fitting the data at earlier times (closer to the injection time) than in E821. B. Lee Roberts, Dipole Moments In Storage Rings AGS/RHIC Workshop,7 June 2006

  23. 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, Dipole Moments In Storage Rings AGS/RHIC Workshop,7 June 2006

  24. Fluorinert (FC40) oil The fast kicker is the major new feature not in the CERN experiment. Kicker Modulator is an LCR circuit, with V ~ 95 kV, I0 ~ 4200 A B. Lee Roberts, Dipole Moments In Storage Rings AGS/RHIC Workshop,7 June 2006

  25. E821 Electron Detectors were Pb-scintillating fiber calorimeters read-out by 4 PMTs. New experiment needs segmented detectors for pileup reduction. B. Lee Roberts, Dipole Moments In Storage Rings AGS/RHIC Workshop,7 June 2006

  26. We count high-energy e- as a function of time. B. Lee Roberts, Dipole Moments In Storage Rings AGS/RHIC Workshop,7 June 2006

  27. New segmented detectors of tungsten/scintillating- fiber ribbons to deal with pile-up • System fits in available space • Prototype under construction • Again the bases will be gated. B. Lee Roberts, Dipole Moments In Storage Rings AGS/RHIC Workshop,7 June 2006

  28. Calibration to a spherical water sample that ties the field to the Larmor frequency of the free protonwp. So we measure wa and wp The magnetic field is measured and controlled using pulsed NMR and the free-induction decay. B. Lee Roberts, Dipole Moments In Storage Rings AGS/RHIC Workshop,7 June 2006

  29. The ± 1 ppm uniformity in the average field is obtained with special shimming tools. We can shim the dipole, quadrupole sextupole independently 0.5 ppm contours B. Lee Roberts, Dipole Moments In Storage Rings AGS/RHIC Workshop,7 June 2006

  30. 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, Dipole Moments In Storage Rings AGS/RHIC Workshop,7 June 2006

  31. The Role of Muon (g-2) • Historically (g-2) has placed a major hurdle in the path of new theories beyond the standard model. • The (g-2) result must fit with other evidence into a consistent picture of new physics, e.g. B. Lee Roberts, Dipole Moments In Storage Rings AGS/RHIC Workshop,7 June 2006

  32. e.g. the (g-2) “discrepancy is quite consistent with other constraints on the SUSY LSP being the dark matter candidate. With CMSSM (constrained minimal supersymmetric model) scalar mass Following Ellis, Olive, Santoso, Spanos from K. Olive gaugino mass B. Lee Roberts, Dipole Moments In Storage Rings AGS/RHIC Workshop,7 June 2006

  33. X2 improvement: (theory and experiment) Future Comparison for DE969 = Dnow B. Lee Roberts, Dipole Moments In Storage Rings AGS/RHIC Workshop,7 June 2006

  34. X2 improvement: (theory and experiment): Future Comparison: DE969= 0 Historically (g-2) has played an important role in restricting models of new physics. B. Lee Roberts, Dipole Moments In Storage Rings AGS/RHIC Workshop,7 June 2006

  35. Summary • E821 Achieved a precision of ± 0.5 ppm • There appears to be a discrepancy between experiment and e+e- based theory • E969 proposes to push the precision down to ± 0.2 ppm • There is lots of work worldwide on the hadronic theory piece, both experimental and theoretical. B. Lee Roberts, Dipole Moments In Storage Rings AGS/RHIC Workshop,7 June 2006

  36. Outlook: • E969 was considered by the national U.S. Particle Physics Project Prioritization Panel (P5) on the 27th of March; report due in September. • Our friends in the theory, e+e- and t communities will continue to work on the hadronic contribution to am. • If both theory can improve by a factor of 2, and experiment can improve by a factor of ≥2, the stage is set for another showdown. B. Lee Roberts, Dipole Moments In Storage Rings AGS/RHIC Workshop,7 June 2006

  37. B. Lee Roberts, Dipole Moments In Storage Rings AGS/RHIC Workshop,7 June 2006

  38. Systematic errors on ωa (ppm) Detector segmentation and lower energy- threshold required for pile-up rejection with higher rates Beam manipulation Cleaner beam Σ* = 0.11 B. Lee Roberts, Dipole Moments In Storage Rings AGS/RHIC Workshop,7 June 2006

  39. E969 (i) (I) (II) (III) (iv) Systematicerrorson ωp(ppm) *higher multipoles, trolley voltage and temperature response, kicker eddy currents, and time-varying stray fields. B. Lee Roberts, Dipole Moments In Storage Rings AGS/RHIC Workshop,7 June 2006

  40. Field systematic uncertainties, ordered by importance B. Lee Roberts, Dipole Moments In Storage Rings AGS/RHIC Workshop,7 June 2006

  41. Precession frequency systematic uncertainties, ordered by importance B. Lee Roberts, Dipole Moments In Storage Rings AGS/RHIC Workshop,7 June 2006

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