(g – 2)  B. Lee Roberts, Dipole Moments In Storage Rings AGS/RHIC Workshop,7 June p. 1/36 Muon (g-2): Past, Present and Future B. Lee Roberts On behalf of the E969 Collaboration bu.edu

(g – 2)  B. Lee Roberts, Dipole Moments In Storage Rings AGS/RHIC Workshop,7 June p. 2/36 (in modern language) (and in English)

(g – 2)  B. Lee Roberts, Dipole Moments In Storage Rings AGS/RHIC Workshop,7 June p. 3/36 Dirac + Pauli moment Schwinger term

(g – 2)  B. Lee Roberts, Dipole Moments In Storage Rings AGS/RHIC Workshop,7 June p. 4/36 g  = 2 s  = 1 / 2

(g – 2)  B. Lee Roberts, Dipole Moments In Storage Rings AGS/RHIC Workshop,7 June p. 5/36

(g – 2)  B. Lee Roberts, Dipole Moments In Storage Rings AGS/RHIC Workshop,7 June p. 6/36

(g – 2)  B. Lee Roberts, Dipole Moments In Storage Rings AGS/RHIC Workshop,7 June p. 7/36 Standard Model Value Muon for (g-2) e vrs.  : relative contribution of heavier things S ?

(g – 2)  B. Lee Roberts, Dipole Moments In Storage Rings AGS/RHIC Workshop,7 June p. 8/36 The hadronic contribution to a  comes from e + e - → hadrons

(g – 2)  B. Lee Roberts, Dipole Moments In Storage Rings AGS/RHIC Workshop,7 June p. 9/36 SignMeasurement  a  / a  sensitivityReference ±± g ≈ 2 5% g = 2 Garwin et al. + %Garwin et al. + (22) 1.9%Charpak et al. + (5) 0.43%Charpak et al. ±± (31)265 ppmBailey et al. ±± (27) 23 ppmBailey et al. ±± (11) 7.3 ppmBailey et al. + (16) 1.3 ppmBrown et al. + (8) 0.7 ppmBennett et al. - (80)(30) 0.7 ppmBennett et al. ±± (63) 0.54 ppmBennett et al. Measurements and Sensitivity of a 

(g – 2)  B. Lee Roberts, Dipole Moments In Storage Rings AGS/RHIC Workshop,7 June p. 10/36 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

(g – 2)  B. Lee Roberts, Dipole Moments In Storage Rings AGS/RHIC Workshop,7 June p. 11/36 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. world average

(g – 2)  B. Lee Roberts, Dipole Moments In Storage Rings AGS/RHIC Workshop,7 June p. 12/36 With an apparent discrepancy at the level of 2.9 ... it’s interesting and you have to work harder to improve the measurement and the theory value ….

(g – 2)  B. Lee Roberts, Dipole Moments In Storage Rings AGS/RHIC Workshop,7 June p. 13/36 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 of Minnesota 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.

(g – 2)  B. Lee Roberts, Dipole Moments In Storage Rings AGS/RHIC Workshop,7 June p. 14/36 We measure the difference frequency between the spin and momentum precession 0 With an electric quadrupole field for vertical focusing

(g – 2)  B. Lee Roberts, Dipole Moments In Storage Rings AGS/RHIC Workshop,7 June p. 15/36 Inflector Kicker Modules Storage ring Central orbit Injection orbit Pions Target Protons (from AGS)p=3.1GeV/c Experimental Technique Muon polarization Muon storage ring injection & kicking focus by Electric Quadrupoles 24 electron calorimeters R=711.2cm d=9cm (1.45T) Electric Quadrupoles

(g – 2)  B. Lee Roberts, Dipole Moments In Storage Rings AGS/RHIC Workshop,7 June p. 16/36 Near sideFar side E821 used a “forward” decay beam, with p  1.7% above p magic to provide a separation at K3/K GeV/c Decay GeV/c Our models show that by quadrupling the quads and going further above p magic the flash is decreased and the muon flux will grow by approximately 2-3 Pedestal vs. Time We base E969 on a modified version of this proven concept.

(g – 2)  B. Lee Roberts, Dipole Moments In Storage Rings AGS/RHIC Workshop,7 June p. 17/36 The Production Target proton beam top view of target

(g – 2)  B. Lee Roberts, Dipole Moments In Storage Rings AGS/RHIC Workshop,7 June p. 18/36 Decay Channel Plenty of room to add more quadrupoles to increase the acceptance of the beamline.

(g – 2)  B. Lee Roberts, Dipole Moments In Storage Rings AGS/RHIC Workshop,7 June p. 19/36 The incident beam must enter through the magnet yoke and through an inflector magnet

(g – 2)  B. Lee Roberts, Dipole Moments In Storage Rings AGS/RHIC Workshop,7 June p. 20/36 Space limitations prevent matching the inflector exit to the storage aperture Upper Pole Piece

(g – 2)  B. Lee Roberts, Dipole Moments In Storage Rings AGS/RHIC Workshop,7 June p. 21/36 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

(g – 2)  B. Lee Roberts, Dipole Moments In Storage Rings AGS/RHIC Workshop,7 June p. 22/36 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 p magic the reduced injection flash will permit us to begin fitting the data at earlier times (closer to the injection time) than in E821.

(g – 2)  B. Lee Roberts, Dipole Moments In Storage Rings AGS/RHIC Workshop,7 June p. 23/36 The 700 ton (g-2)  precision storage ring Muon lifetime t  = 64.4  s (g-2) period t a = 4.37  s Cyclotron period t C = 149 ns Scraping time (E821) 7 to 15  s Total counting time ~700  s Total number of turns ~4000

(g – 2)  B. Lee Roberts, Dipole Moments In Storage Rings AGS/RHIC Workshop,7 June p. 24/36 The fast kicker is the major new feature not in the CERN experiment. Kicker Modulator is an LCR circuit, with V ~ 95 kV, I 0 ~ 4200 A oil Fluorinert (FC40)

(g – 2)  B. Lee Roberts, Dipole Moments In Storage Rings AGS/RHIC Workshop,7 June p. 25/36 E821 Electron Detectors were Pb-scintillating fiber calorimeters read-out by 4 PMTs. New experiment needs segmented detectors for pileup reduction.

(g – 2)  B. Lee Roberts, Dipole Moments In Storage Rings AGS/RHIC Workshop,7 June p. 26/36 We count high-energy e - as a function of time.

(g – 2)  B. Lee Roberts, Dipole Moments In Storage Rings AGS/RHIC Workshop,7 June p. 27/36 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.

(g – 2)  B. Lee Roberts, Dipole Moments In Storage Rings AGS/RHIC Workshop,7 June p. 28/36 The magnetic field is measured and controlled using pulsed NMR and the free-induction decay. Calibration to a spherical water sample that ties the field to the Larmor frequency of the free proton  p. So we measure  a and  p

(g – 2)  B. Lee Roberts, Dipole Moments In Storage Rings AGS/RHIC Workshop,7 June p. 29/36 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

(g – 2)  B. Lee Roberts, Dipole Moments In Storage Rings AGS/RHIC Workshop,7 June p. 30/36 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 improvements will involve new scraping scheme, lower thresholds, more complete digitization periods, better energy calibration Systematic uncertainty (ppm) E969 Goal Magnetic field –  p Anomalous precession –  a Statistical uncertainty (ppm) Total Uncertainty (ppm)

(g – 2)  B. Lee Roberts, Dipole Moments In Storage Rings AGS/RHIC Workshop,7 June p. 31/36 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.

(g – 2)  B. Lee Roberts, Dipole Moments In Storage Rings AGS/RHIC Workshop,7 June p. 32/36 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 gaugino mass Following Ellis, Olive, Santoso, Spanos from K. Olive

(g – 2)  B. Lee Roberts, Dipole Moments In Storage Rings AGS/RHIC Workshop,7 June p. 33/36 X2 improvement: (theory and experiment) Future Comparison for  E969 =  now

(g – 2)  B. Lee Roberts, Dipole Moments In Storage Rings AGS/RHIC Workshop,7 June p. 34/36 X2 improvement: (theory and experiment): Future Comparison:  E969  Historically (g-2) has played an important role in restricting models of new physics.

(g – 2)  B. Lee Roberts, Dipole Moments In Storage Rings AGS/RHIC Workshop,7 June p. 35/36 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.

(g – 2)  B. Lee Roberts, Dipole Moments In Storage Rings AGS/RHIC Workshop,7 June p. 36/36 Outlook: E969 was considered by the national U.S. Particle Physics Project Prioritization Panel (P5) on the 27 th of March; report due in September. Our friends in the theory, e + e - and  communities will continue to work on the hadronic contribution to a   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.

(g – 2)  B. Lee Roberts, Dipole Moments In Storage Rings AGS/RHIC Workshop,7 June p. 37/36

(g – 2)  B. Lee Roberts, Dipole Moments In Storage Rings AGS/RHIC Workshop,7 June p. 38/36 σ systematic E969 Pile-up AGS Background 0.10 * Lost Muons Timing Shifts E-Field, Pitch *0.05 Fitting/Binning * CBO Beam Debunching 0.04 * Gain Change total Systematic errors on ω a (ppm) Σ* = 0.11 Cleaner beam Beam manipulation Detector segmentation and lower energy- threshold required for pile-up rejection with higher rates

(g – 2)  B. Lee Roberts, Dipole Moments In Storage Rings AGS/RHIC Workshop,7 June p. 39/36 Systematic errors on ω p (ppm) *higher multipoles, trolley voltage and temperature response, kicker eddy currents, and time-varying stray fields. E969 (i ) (I) (II) (III) (iv)

(g – 2)  B. Lee Roberts, Dipole Moments In Storage Rings AGS/RHIC Workshop,7 June p. 40/36 Field systematic uncertainties, ordered by importance SourceE821 (ppm) E969 (ppm) Comment Calibration of trolley probe Improved shimming in the transfer region; improved registration of trolley location in ring Interpolation with fixed probes Repairs and retuning of a number of probes to improve the sampling of the ring field Absolute calibration0.05 Could improve if 3 He based probe Trolley measurements of B More frequent trolley runs; mechanical maintenance of trolley drive and garage; Extensive measurements of trolley NMR probe active volumes Muon distribution Simulations of storage ring; improved shimming “Other” eddy currents higher multipoles trolley temp and PS response in situ measurement of eddy currents Improved shimming Modifications to trolley and PS Total

(g – 2)  B. Lee Roberts, Dipole Moments In Storage Rings AGS/RHIC Workshop,7 June p. 41/36 Precession frequency systematic uncertainties, ordered by importance SourceE821 (ppm) E969 (ppm) Comments Gain stability Full WFD samples recorded; stability of laser calibration with local reference detectors; single-phase WFDs Lost muons New scraping scheme; improved kick Pileup:T method Q method (not applicable) Recording all samples, no threshold, will eliminate ambiguity from low-energy pulses CBO: coherent betatron oscillations Improved kick; new scraping; taller calorimeters E and pitch correction0.05 Should be improved with better storage ring simulation, but we keep it as is for now Timing shifts Laser calibration; precision determined by amount of data collected AGS background0.01 Sweeper magnet maintained Fit procedure and bin width Limited by number of simulated trials performed Vertical waist CBO related; see above Other small effects< 0.03 < 0.02 These either scale with the data set size or from the simulations demonstrating “no effect” Total