Final Results of the Muon g-2 Experiment at BNL

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1 Final Results of the Muon g-2 Experiment at BNL Petr Shagin on behalf of E821 Collaboration SLAC Summer Institute, August 10th, SLAC Summer Institute Petr Shagin p.1/34

2 Overview Introduction Muon g-2 experiment at BNL Analysis of the 2001 data set Standard Model Prediction SUSY Conclusions and Outlook 2004 SLAC Summer Institute Petr Shagin p.2/34

3 Dipole Magnetic Moment Dirac: Hadrons Large deviation for a point-like spin- quark substructure: particle Leptons Small deviation coupling to virtual fields: # Deviation from g=2 is characterized by Anomaly $&% 2004 SLAC Summer Institute Petr Shagin p.3/34

4 ) ( The Anomalous Magnetic Moment µ γ µ µ µ µ µ α a = 2 π Muon anomaly is times more sensitive to the new physics compared to the electron anomaly. #%$ #'& 2004 SLAC Summer Institute Petr Shagin p.4/34

5 Muon g-2 Experiment at BNL Muon storage ring: Radius 7112 mm Aperture 9 cm Magnetic field 1.45 T Momentum GeV/c electric quadrupole settings: n = ; SLAC Summer Institute Petr Shagin p.5/34

6 Muon g-2 Collaboration Most recent paper: 70 authors, 11 institutions, 5 countries Boston University Boston, Massachusetts, USA Brookhaven National Laboratory Upton, New York, USA Budker Institute of Nuclear Physics Novosibirsk, Russia Cornell University Ithaca, New York, USA Universität Heidelberg Heidelberg, Germany University of Illinois Urbana, Illinois, USA KEK Tsukaba, Japan Kernfysisch Versneller Instituut Groningen, The Netherlands University of Minnesota Minneapolis, Minnesota, USA Tokyo Institute of Technology Tokyo, Japan Yale University New Haven, Connecticut, USA Funding: Department of Energy, National Science Foundation, National Computational Science Alliance, German Bundesminister für Bildung und Forschung, Russian Ministry of Science, and U.S.-Japan Agreement in High-Energy Physics SLAC Summer Institute Petr Shagin p.6/34

7 ) Spin Precession and Magic Momentum p Muon in flight: θ σ B Orbiting particles will escape on the top or bottom. Need vertical focusing We used quadrupole electric field to stabilize muon orbit in vertical direction. for GeV/c; = 64 s 2004 SLAC Summer Institute Petr Shagin p.7/34

8 Muon Beam and Injection 24 GeV/c AGS protons hit the target 3.1 GeV/c; polarised Target g-2 beam line muon beam superconducting inflector injection point central injection orbit central storage orbit Collimator K3-K4 Q1 D1 D4 Collimator K1-K2 P1 Beam Stop Q15 Q18 D5 P2 IC8 Inflector D6 radius cm 92.6o 18o 18 o kicker 1 kicker 2 kicker 3 Target Dipole Magnets D1-D7 g-2 ring 7.7 cm Pitching Magnets P1, P2 Quadrupole Magnets Q1-Q29 Ion Chambers IC1-IC8 Collimators opposite to the ; high energy spin; are preferentially emitted ν e ν µ Muon Rest Frame - µ momentum spin e SLAC Summer Institute Petr Shagin p.8/34

using 17 calibrated NMR probes in a trolley. vertical distance [cm] 4 3 2 1 0-1 -2-3 -4 0.0-0.5-1.0 0.0 1.5 1.0 0.5 0.

9 Magnetic Field: Uniformity 1.45T magnetic field was measured in terms of the proton NMR frequency ( ) inside the vacuum chamber every couple of days using 17 calibrated NMR probes in a trolley. vertical distance [cm] radial distance [cm] B-B 0,0 [ppm] 0.5ppm contours are 725 nt over an average field 1.45T 2004 SLAC Summer Institute Petr Shagin p.9/34

10 Magnetic Field Systematic Uncertainty Two independent 0.05 ppm. analyses completed; both agree within Effect 2000 [ppm] 2001 [ppm] Absolute calibration of standard probe Calibration of trolley probes Trolley measurements of Interpolation with fixed probes Uncertainty from muon distribution Others Total Main improvements: more calibrations, new trolley position encoding system, less magnet ramping, more trolley measurement runs 2004 SLAC Summer Institute Petr Shagin p.10/34

Station 20 2 19 3 18 4 17 5 16 6 15 7 14 8 13 12

11 . Measuring e e e Beam Inflector Vacuum Chamber Regular Vacuum Chamber Detector Station SLAC Summer Institute Petr Shagin p.11/34

12 Data Pulse height (ADC counts) Time (ns) Complete waveform of the calorimeter signal was digitized by WFD with 2.5 ns sampling. Parameterize pulse shape to reconstruct energy and time of the electron Histogram: number of decay electrons vs fitted pulse time 2004 SLAC Summer Institute Petr Shagin p.12/34

13 Experimental Precision 1 Relative Amplitude Number N Asymmetry A 0.4 NA² Energy Threshold [GeV] 2004 SLAC Summer Institute Petr Shagin p.13/34

14 ) The 2001 data events with s, GeV Million Events per 149.2ns s s s s s s Time modulo 100µs [µs] Five parameters function: - is number of events; - Asymetry (oscillations amplitude); - spin precession frequency - is the phase (angle between the spin and momentum vectors at the moment of injection) 2004 SLAC Summer Institute Petr Shagin p.14/34

15 Data Analyses Five independent blind data analyses were performed. Goal: Describe the time spectrum of the electron counts adequately using a function with as few parameters as possible. To obtain an acceptable /dof with 4 events in one histogram of 4500 bins. Small effects can contribute due to the huge number of events detected. PMT Gain: changes effective ; can be reconstructed from vs time pileup/overlapping signals: affects, and can be reconstructed from data itself muon loss: affects ; couples weakly to can be reconstructed from scintillator detectors Coherent Betatron Oscillations (CBO) Data were taken for two different quadrupole settings to avoid dangerous spin resonances and to minimize systematic uncertainty related to beam dynamics 2004 SLAC Summer Institute Petr Shagin p.15/34

16 * Ratio Method Ratio Million Counts per 149.2ns Time [ns] Time [ns] ( )( & &' %$ # Slow effects are largely cancelled for 2004 SLAC Summer Institute Petr Shagin p.16/34

17 Ratio Method N n(t+ta/2) n(t-ta/2) n(t) Time [ns] r(t) Time [ns] 2004 SLAC Summer Institute Petr Shagin p.17/34

18 Consistency of Fit Results R-Ro [ppm] offset R-Ro [ppm] 120 Chi2 / ndf = / 22 p0 = ± Fit Start Time [ns] 2 x Detector R-Ro [ppm] Chi2 / ndf = / 6 p0 = ± R [ppm] R [ppm] vs Run 250 Chi2 / ndf = 1019 / 96 p0 = ± E [GeV] Run 2004 SLAC Summer Institute Petr Shagin p.18/34

19 Comparison of the 5 Analyses R [ppm] 110 Chris Jon Mario Peter Xiaobo 109 n = n = combined 107 Chris - Asymmetry-weighted multiparameter analysis Jon - Ratio method; CBO included in fit function Mario, Xiaobo - Multiparameter analyses Peter - Ratio method analysis 2004 SLAC Summer Institute Petr Shagin p.19/34

20 Error table for Effect Uncertainty [ppm] Statistics Overlapping pulses (pileup) Gain changes Lost muons Beam dynamics Other Total systematics Total uncertainty Unfortunately still limited by statistics SLAC Summer Institute Petr Shagin p.20/34

21 ) $ Determining Analyses for and were finalized separately and done independently. Secret offsets were removed. with from muonium spectroscopy [W. Liu et al., PRL 82, 711] ppm 2004 SLAC Summer Institute Petr Shagin p.21/34

22 Standard Model Prediction µ µ γ γ γ e, µ µ µ γ γ γ h µ µ γ Ζ 2004 SLAC Summer Institute Petr Shagin p.22/34

23 Hadronic Vacuum Polarization Low-energy QCD is non-perturbative, so HVP contribution can not be calculated reliably from first principles fortunately data can help...contribution can be determined to hadrons through dispersion from integral. electron-positron annihilation q q hadrons # ppm M. Davier, S. Eidelman, A. Höcker and Z. Zhang, Eur. Phys. J. C31, 503 (2003) 2004 SLAC Summer Institute Petr Shagin p.23/34

24 Hadronic decay Assume exact isospin symmetry; from CVC: Indirectly e + e γ ν τ hadrons CVC W hadrons exp rad exp rad SU(2) M. Davier, S. Eidelman, A. Höcker and Z. Zhang, Eur. Phys. J. C31, 503 S. Ghozzi and F. Jegerlehner, hep-ph/ SLAC Summer Institute Petr Shagin p.24/34

25 The e e / Discrepancy 0.3 ( F π 2 [ee] F π 2 [τ]) / F π 2 [τ] τ data (ALEPH) CMD-2 CMD OLYA DM1 CLEO ± 0.12 ± 0.42 OPAL ± 0.17 ± 0.29 L ± 0.16 ± 0.10 ALEPH preliminary ± 0.10 ± e + e CVC ± 0.32 τ Average ± s (GeV 2 ) B(τ ν τ π π o ) (in %) 2004 SLAC Summer Institute Petr Shagin p.25/34

26 Comparison to theory - µ Avg. [e + µ [τ] ] aµ - e Experiment Theory SLAC Summer Institute Petr Shagin p.26/34

27 # New Physics Beyond Standart Model? there is a discrepancy, it is a good region for SUSY SUSY: µ χ ν χ µ + µ χ 0 µ µ µ γ γ (A.Czarnecki and W.J. Marciano hep-ph/ ) (for 4 < < 40 ) % $ 2004 SLAC Summer Institute Petr Shagin p.27/34

28 # Conclusions and Outlook anomaly ppm New measurement of are statistically compatible (CPT test) and Results for Average anomaly ppm is % $ # Constrains for 2004 SLAC Summer Institute Petr Shagin p.28/34

29 Hadron Production Cross-Section 6 5 ω Φ e + e J/ψ 1S ψ 2S hadrons ψ 3770 QCD 4 R exclusive data BES γγ2 Crystal B. PLUTO s (GeV) ϒ 1S ϒ 2S 3S 4S 5 4 ϒ ϒ R e + e hadrons QCD PLUTO LENA Crystal B. MD1 JADE MARK J s (GeV) [M. Davier et al., hep-ph/ ] 2004 SLAC Summer Institute Petr Shagin p.29/34

30 The Radiative Return Method DA NE, PEP-II: operate at fixed CM energies (1.02 GeV, GeV) Hadronic energy scan via Initial State Radiation γ + e γ h e Published KLOE results [hep-ex/ ] confirm Novosibirsk e e data. BaBaR results upcoming SLAC Summer Institute Petr Shagin p.30/34

31 Electroweak interactions γ γ γ µ µ Z 0 W W µ µ γ µ µ ν µ QED (through four loops + five loops estimated): ppm # Weak (through two loops): ppm 2004 SLAC Summer Institute Petr Shagin p.31/34

32 Hadronic light-by-light γ H γ µ µ ( ppm) K. Melnikov and A. Vainshtein, hep-ph/ SLAC Summer Institute Petr Shagin p.32/34

33 Evolution of the experimental precision + CERN µ CERN µ BNL97 µ BNL98 µ BNL99 µ BNL00 µ BNL01 µ a µ 2004 SLAC Summer Institute Petr Shagin p.33/34

34 Corrections to Electric field correction: Effect of term on non-magic muons ( calculated from measured radial distribution: ppm ); Pitch correction: Vertical betatron oscillation changes the rms angle between muon orbit and correction term in : ppm 2004 SLAC Summer Institute Petr Shagin p.34/34

Muon (g 2) at JPARC. Five to Ten Times Better than E821. B. Lee Roberts. Department of Physics Boston University BOSTON UNIVERSITY

Muon (g 2) at JPARC. Five to Ten Times Better than E821. B. Lee Roberts. Department of Physics Boston University BOSTON UNIVERSITY Muon (g 2) at JPARC Five to Ten Times Better than E821 B. Lee Roberts roberts@bu.edu http://physics.bu.edu/roberts.html Department of Physics Boston University B. Lee Roberts, JPARC LOI Presentation, 26