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Muon (g-2) to 0.2 ppm

Muon (g-2) to 0.2 ppm. B. Lee Roberts Department of Physics Boston University. roberts @ bu.edu http://physics.bu.edu/roberts/html. (in modern language) (and in English). Dirac + Pauli moment. Standard Model Value for (g-2). ?.

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Muon (g-2) to 0.2 ppm

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  1. Muon (g-2) to 0.2 ppm B. Lee Roberts Department of Physics Boston University roberts @ bu.edu http://physics.bu.edu/roberts/html B. Lee Roberts e+e- collisions f to y : Novosibirsk 1 March 2006

  2. (in modern language) (and in English) B. Lee Roberts e+e- collisions f to y : Novosibirsk 1 March 2006

  3. Dirac + Pauli moment B. Lee Roberts e+e- collisions f to y : Novosibirsk 1 March 2006

  4. Standard Model Value for (g-2) ? e vrs. m : relative contributionof heavier things B. Lee Roberts e+e- collisions f to y : Novosibirsk 1 March 2006

  5. One reason that I’m here is the relationship between e+e- annihilation and am B. Lee Roberts e+e- collisions f to y : Novosibirsk 1 March 2006

  6. 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 e+e- collisions f to y : Novosibirsk 1 March 2006

  7. 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 e+e- collisions f to y : Novosibirsk 1 March 2006

  8. With an apparent discrepancy at the level of 2.6 s . . . it’s interesting and you have to work harder to improve the measurement and the theory value …. B. Lee Roberts e+e- collisions f to y : Novosibirsk 1 March 2006

  9. A (g-2)m Experiment to ± 0.2 ppmPrecision –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; D. Grigoriev B.I. Khazin S.I. Redin Yuri M. Shatunov, E. Solodov – Budker Institute; F.E. Gray B. Lauss E.P. Sichtermann – UC Berkely and LBL; Y. Orlov – Cornell University; J. Crnkovic ,P. Debevec D.W. Hertzog, P. Kammel S. Knaack, R. McNabb – University of Illinois UC; K.L. Giovanetti – James Madison University; K.P. Jungmann C.J.G. Onderwater – KVI Groningen; T.P. Gorringe, W. Korsch – U. Kentucky, P. Cushman – Minnesota; Y. Arimoto, Y. Kuno, A. Sato, K. Yamada – Osaka University; S. Dhawan, F.J.M. Farley – Yale University B. Lee Roberts e+e- collisions f to y : Novosibirsk 1 March 2006

  10. We measure the difference frequency between the spin and momentum precession With an electric quadrupole field for vertical focusing 0 B. Lee Roberts e+e- collisions f to y : Novosibirsk 1 March 2006

  11. Experimental Technique Spin Momentum Central orbit Kicker Modules R=711.2cm d=9cm Electric Quadrupoles polarized m 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 e+e- collisions f to y : Novosibirsk 1 March 2006

  12. E821: used a “forward” decay beam Pions @ 3.115 GeV/c Decay muons @ 3.094 GeV/c Near side Far side This baseline limits how early we can fit data Pedestal vs. Time B. Lee Roberts e+e- collisions f to y : Novosibirsk 1 March 2006

  13. The Production Target top view of target proton beam B. Lee Roberts e+e- collisions f to y : Novosibirsk 1 March 2006

  14. Decay Channel Plenty of room to add more quadrupoles to increase the acceptance of the beamline. B. Lee Roberts e+e- collisions f to y : Novosibirsk 1 March 2006

  15. Expect for both sides E969: will use a “backward” decay beam new front-end Pions @ 5.32 GeV/c increase of proton beam Decay muons @ 3.094 GeV/c Approximately the same muon flux is realized No hadron-induced prompt flash Then we quadruple the number of quadrupoles in the decay channel x 1 more muons > x 2 B. Lee Roberts e+e- collisions f to y : Novosibirsk 1 March 2006

  16. The incident beam must enter through the magnet yoke and through an inflector magnet B. Lee Roberts e+e- collisions f to y : Novosibirsk 1 March 2006

  17. Upper Pole Piece The mismatch between the inflector exit and the storage aperture + imperfect kick causes coherent beam oscillations B. Lee Roberts e+e- collisions f to y : Novosibirsk 1 March 2006

  18. 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 e+e- collisions f to y : Novosibirsk 1 March 2006

  19. 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 e+e- collisions f to y : Novosibirsk 1 March 2006

  20. 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 e+e- collisions f to y : Novosibirsk 1 March 2006

  21. E821 Electron Detectors were Pb-scintillating fiber calorimeters read-out by 4 PMTs. New experiment needs segmented detectors for pileup reduction. B. Lee Roberts e+e- collisions f to y : Novosibirsk 1 March 2006

  22. We count high-energy e- as a function of time. B. Lee Roberts e+e- collisions f to y : Novosibirsk 1 March 2006

  23. 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 e+e- collisions f to y : Novosibirsk 1 March 2006

  24. 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 e+e- collisions f to y : Novosibirsk 1 March 2006

  25. 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 e+e- collisions f to y : Novosibirsk 1 March 2006

  26. E969 needs 10 times more muons than E821 stored. • Open Inflector X2 • Backward Beam X1 • Quadruple the Quadrupoles X 2-3 Beam increase design factor X 5 Absence of injection flash will permit us to begin analyzing data much earlier B. Lee Roberts e+e- collisions f to y : Novosibirsk 1 March 2006

  27. 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 e+e- collisions f to y : Novosibirsk 1 March 2006

  28. 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. • Thanks to all of you who are working on these problems! ! B. Lee Roberts e+e- collisions f to y : Novosibirsk 1 March 2006

  29. Outlook: • E969 will be considered by the national U.S. Particle Physics Project Prioritization Panel (P5) at the end of March • We hope that 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 2.5, the stage is set for another showdown. B. Lee Roberts e+e- collisions f to y : Novosibirsk 1 March 2006

  30. Thanks to the organizers for this excellent workshop! Thank you СПАСИБО B. Lee Roberts e+e- collisions f to y : Novosibirsk 1 March 2006

  31. B. Lee Roberts e+e- collisions f to y : Novosibirsk 1 March 2006

  32. Systematic errors on ωa (ppm) Detector segmentation and lower energy- threshold required for pile-up rejection with higher rates Beam manipulation Backward beam Σ* = 0.11 B. Lee Roberts e+e- collisions f to y : Novosibirsk 1 March 2006

  33. 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 e+e- collisions f to y : Novosibirsk 1 March 2006

  34. E969 Builds on the apparatus and Experience of E821 • AGS Proton Beam 12 – bunches from the AGS 60 Tp total intensity • 0op Beam • p decay channel • m Beam injected into the ring through a superconducting inflector • Fast Muon Kicker • Precision Magnetic Storage Ring • Electron calorimeters, custom high-rate electronics and wave-form digitizers B. Lee Roberts e+e- collisions f to y : Novosibirsk 1 March 2006

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