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The g-2 Collaboration

Does g-2 point to new physics?: Current Status and Future Plans. The g-2 Collaboration

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The g-2 Collaboration

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  1. Does g-2 point to new physics?: Current Status and Future Plans The g-2 Collaboration Boston University, Brookhaven National Laboratory, University of Heidelberg (* KVI), University of Illinois, University of Minnesota, Budker Institute, Yale University, KEK, Tokyo Institute of Technology, Cornell University

  2. The Magnetic Moment (e+e-, m+m-,t+t-) m m m g g g m =geh s 2mc 2 Wheregis thegyromagnetic ratiowhich relates the angular momentum to the intrinsic spin g=2for charged, point-like, spin 1/2 particles. Hadronsg(neutron) = -3.82 ≠ 0 Large deviations => quark substructureg(proton) = +5.58 ≠ 2 Leptons Small deviations => coupling to virtual fields Deviations from g=2 are characterized by the Anomaly: a =g-2 (a~ .001 for a lepton) 2

  3. Coupling to X goes asmm2/mX2factor of 40,000 compared to e Muon anomalous magnetic moment am(SM) = am(QED) + am(weak) +am(had) x 10-10 am(QED) = 11658471.935 (.143) BNL E821 data

  4. zo m µ µ W W µ µ B field Coupling to X goes asmm2/mX2factor of 40,000 compared to e Muon anomalous magnetic moment am(SM) = am(QED) + am(weak) +am(had) x 10-10 am(QED) = 11658471.935 (.143) + am(weak) = 15.4__ (.2) +3.89 BNL E821 data -1.94(Higgs < 0.01)

  5. Coupling to X goes asmm2/mX2factor of 40,000 compared to e Muon anomalous magnetic moment am(SM) = am(QED) + am(weak) +am(had) x 10-10 am(QED) = 11658471.935 (.143) + am(weak) = 15.4__ (.2) + am(had1sto) = 696.3__ (7.2) + am(had h.o.) = -10.0__ (.6) BNL E821 data Requires Data

  6. Coupling to X goes asmm2/mX2factor of 40,000 compared to e Muon anomalous magnetic moment am(SM) = am(QED) + am(weak) +am(had) x 10-10 am(QED) = 11658471.935 (.143) + am(weak) = 15.4__ (.2) + am(had1sto) = 696.3__ (7.2) + am(had h.o.) = -10.0__ (.6) + am(hadl-by-l) = + 13.6__ (2.5) BNL E821 data

  7. D am= any new physics Coupling to X goes asmm2/mX2factor of 40,000 compared to e Muon anomalous magnetic moment am(SM) = am(QED) + am(weak) +am(had) x 10-10 am(QED) = 11658471.935 (.143) + am(weak) = 15.4__ (.2) + am(had1sto) = 696.3__ (7.2) + am(had h.o.) = -10.0__ (.6) + am(hadl-by-l) = + 13.6__ (2.5) BNL E821 data

  8. How to Measure a Magnetic Moment Brookhaven provides the pions from protons on nickel tgt Forward-going daughter muons are polarized 0 m- p- nm

  9. How to Measure a Magnetic Moment wc (Tc = 149 ns) wa = ws- wc (precesses ~120 per cycle) ws = 1+g (g-2) eB and wc = eB 2 mcg mcg wa = ws - wc = (g-2) eB 2 mc (am- ) b x E e mc 1 g2 -1 Quadrupole E field gives additional term in wa : + Which vanishes at the “magic momentum” of 3.094 GeV/c

  10. WEAK-FOCUSSING MUON STORAGE RING B = 1.45 T Pm= 3.094 GeV/c Rring = 7.112 m Rstor = 4.5 cm Kicker Quad Quad Inflector 24 SciFi Calorimetersrecord time and energy of decay e+ (or e-) nmne m-e- Quad Calorimeters select high energy e’s These e’s are preferentially emitted in the direction of the m spin Quad

  11. 2001 data set: 4 billion e+ (E > 1.8 GeV, t > 32 ms after injection) Cyclotron Frequency at early times g-2 Precession Frequency after debunching Fit for g,m radial distribution, bxE correction: (0.47 + 0.05) ppm Million evts per 149.2 ns Fit for wa: No e-t/gt (1 + A cos (wat +j)) is no longer good enough.

  12. m e Energy Spectrum late time(no pileup) early + late early + late(corrected) Main Disturbances • Pileup of real pulses <5 ns apart1% at earliest times: model and subtract • Muon Lossesbump beam and scrape (first 11 ms) scintillator paddles measure triples • Rate dependent calorimeter responsechanges the effective Ethrin situ laser calibration system • Bunched beamrandomize time spectrum in bins of Tcyclotron • Coherent Betatron Oscillations image of the inflector exit moves around the ring as a beat frequency of wc and wb fiber harp and traceback chamber measure stored muon profile vs time

  13. Consistency between analyzers checked G2off productionMulti-parameter quad corrections G2Too productionMulti-parameter, Eth=1.5 GeV asymmetry-weighted, G2off productionMulti-parameter G2off production9-parameter ratio G2Too production3 - parameter ratio with cancellation Low n (black), high n (clear), combined (red) data sets.

  14. Measuring the Magnetic Field 0.5 ppm contours are 750 nT over an average field of 1.45 Tesla. muon sees the field averaged over azimuth vertical distance (cm) -4 -3 -2 -1 0 1 2 3 4 -4 -3 -2 -1 0 1 2 3 4 17 calibrated NMR probes inside the trolley measure the field every cm horizontal distance (cm)

  15. Blind Analysis Decay positrons NMR wa = am e B mp B = h wp mc am = Rl + R where R = wa / wp is measured by E821 and l = mm / mpfrom muonium hyperfine structure • Offline Team (5 analyses) Magnet Team (2 analyses) • wa wp • Both w’s and all analyses have computer-generated secret offsets. • Study stability of R under all conditions • Finish all studies and assign all uncertainties BEFORE revealing offset.

  16. Results from the 2000/2001 datasets & World Average In order to use the t-decay data, you need CVC – its not perfect. Isospin violation - include r mass differences? Experimental problems - normalization? am x 10 -10 - 11659000 World average am = 11659208(6) x 10-10 Recall am = R/(l-R) where we measure R = wa/wpand where l = mm/mp = 3.18334539(10) Quote CPT results in terms of DR = (3.5 + 3.6) x 10-6

  17. Taking Dam = am(exp)-am(thry): the details are still changing… QED 11658472.07 (.12) 5-loop: Laporta & Remiddi + Kinoshita & Nio update up from 11658470.57 (.29) EW LO 19.5 1st order e.g. Fujikawa, Lee, Sanda ’72EW HO -4.07(2) 2-loop, NL+LL Czarnecki, Krause, Marciano ‘96 updated: Czarnecki, Marciano, Vainshtein ’03 15.4 (.2)agrees with 15.3 (.2) Knecht, Peris, Perrottet, DeRafael Had LO (e+e-) 696.3 (6.2)(3.6) Davier,Eidelman, Hoecker, Zhang hep-ph/0308213v2692.4 (5.9)(2.4) Hagiwara, Martin, Nomura, Teubner hep-ph/0312250 add KLOE 694.4 (5.6)(3.6)Davier, Hoecker, Eidelman, Zhang ICHEP04add QCD 693.4 (5.3)(3.5) Had NL -9.8 (.1) Hagiwara, Martin, Nomura, Teubneragrees with -10.1 (.6) Krause ’97 Had l-by-l 13.6 (2.5) Melnikov & Vainstein hep-ph/0312226up from 8.0 (4.0) Nyffler ’02 World Avg (moving target) D am = 25.2 (9.2) x 10-102.7 susing the latest – See Hoecker’s talk this morning…

  18. Improvement in Theory will continue over the next decade Precision in the dispersion integral CMD-2 (e+e- at 0.3-1.4) has 5 times more e+e- data still unanalyzed VEPP-2000 upgrade (2.0 GeV, 10 x L, CMD-3, SND) More data from Beijing (e+e- from 2-5 GeV) after intensity upgrade Radiative return measurements at BaBar, KLOE, (Belle?)  Estimate am(had VP from e+e-)  0.3 ppm Other Avenues Further understanding t vs e+e- discrepancy (Belle, Cleo2) Improvements in hadronic light-by-light term Lattice gauge calculations 0.6% 0.1% (2010)

  19. New KLOE data using “radiative return” method Initial State Radiationlowers the CM energy and also tags the event BaBar is also doing this. They can measure e+e-  m+m- directly since photon is hard

  20. Evolution of the Experimental Uncertainties Data Set: 1997 1998 1999 2000 2001 p-injection kicker installed 1st long run new inflector reverse polarity field stabilized 12 M e+ 84 M e+ 1 B e+ 4 B e+ 4 B e-Statistics (Ne above Ethr)12.5 ppm 4.9 ppm 1.25 ppm 0.6 ppm 0.7 ppm Systematics2.9 ppm 1 ppm 0.5 ppm 0.4 ppm 0.3 ppm dwa 2.6 ppm 0.7 ppm 0.3 ppm 0.3 ppm 0.21 ppm Dominated byWFD threshold pileup pileup coherent betatron gain stability pion flash AGS mistune AGS mistune m loss, pileup m loss dwp1.3 ppm 0.5 ppm 0.4 ppm 0.24 ppm 0.17 ppm Dominated bythermal fluctuations trolley position trolley position trolley position trolley position no active feedback inflector inflector Still statistics dominated!

  21. Proposal P969 for another Run at BNL Improve am by a factor of 2.5 to match expected theory improvement500 hrs setup (pulse-on-demand) + 1500 hrs dedicated5 x faster than before by higher intensity and the following changes Provide More Muons Double number of beamline quads + use backward-going muons Flux x 2.1 and no accompanying pions to create “flash” Store More Muons Open-end inflector design + 4th muon kicker m’s x 2 and reduced systematics from Coherent Betatron Oscillation Handle Higher rates Increased Calorimeter Segmentation Continuous WFD, Commercial MTDC’s, IIncrease DAQ throughput Improve B-field Measurement In situ measurements of field changes with kicker eddy current Trolley position calibration and mapped NMR positions

  22. Evolution of the Experimental Uncertainties Data Set: 1999 2000 2001 2006-7 1st long run new inflector reverse polarity improved BNL (20 week run) 1 B e+ 4 B e+ 4 B e- 70 B e+Statistics (Ne above Ethr) 1.25 ppm 0.6 ppm 0.7 ppm 0.14 ppm Systematics 0.5 ppm 0.4 ppm 0.3 ppm 0.15 ppm dwa 0.3 ppm 0.3 ppm 0.21 ppm 0.11 ppm Dominated by pileup coherent betatron gain stability AGS mistune m loss, pileup m loss, pileup dwp 0.4 ppm 0.24 ppm 0.17 ppm 0.11 ppm Dominated by trolley position trolley position trolley position trolley position inflector

  23. In CMSSM, am can be combined with b sg, cosmological relic density Wh2, and LEP Higgs searches to constrain c mass Da = 24 x 10-10 favors higher tan b andavoids coannihilation region From Keith Oliveusing the g-2 PRL (2003) Dam and the method described in Ellis, Olive, Santoso, Spanos Excluded by direct searches Allowed 2s band am(exp)– am(e+e- thy) cosmologically preferred region Wh2= 0.09 - 0.12 Excluded for neutral dark matter

  24. The CMSSM plot with error on Dam of 4.6 x 10-10(assuming better theory and a new BNL g-2 experiment) Dam=24(4.6) x 10-10 (discrepancy at 6 s) Dam = 0 (4.6) x 10-10 Current Discrepancy Standard Model

  25. How would a non-zero electric dipole moment affect g-2?

  26. Access to the vertical oscillation comes from auxiliary detectors listed in order of segmentation: • FSD: 5 scintillator bars in front of detector (9 stations) gives average y-position and rms width. • PSD: 32 x 20 tile/fiber strips. (2 – 5 stations) gives x-y position and profile shape • Traceback: Strawtube tracking chamber (1 station) gives vertical angle For example, a fit to the average y-position in the FSD vs time yields the amplitude of the “out-of-phase” component.

  27. Data analysis on the 2000 & 2001 runs continues Look for an edm paper in the next couple months Reduced the limit on edm by ~ x4 Reduced potential effect on wa by ~ x16 Also work is proceeding on Edm of m- (2001 data with PSD – improve another x2) Combine with g to get best m- lifetime (20 ppm)Comparison of m+ vs m- lifetime Limit on sidereal variation dm+ < 2.8 x 10-10 e-cm (95% C.L.) using 2000 data & FSDs (McNabb et al, hep-ex/0407008) Precise lifetime G

  28. Conclusions • Things are getting exciting • One can reasonably hope to reduce the error on Dam by a factor of 3 over the next decade provided we have another run. • If the g-2 hint is real & due to SUSY  then the new particles will be seen in the LHC • If WIMP’s are neutralino’s consistent with g-2  then CDMS will see them in the next few years. • If LHC sees new particles, but CDMS doesn’t find WIMP’s  the particles are not supersymmetric and/or dark matter is not supersymmetric • If g-2 shows a discrepancy, but nothing is seen in LHC or CDMS II  then we need to examine extra dimensions, edm’s • Many possibilities beyond simple confluence…

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