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

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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 ICHEP Aug 16-22, 2004 Beijjing, China

2 ICHEP Aug 16-22, 2004 Beijjing, China
The Magnetic Moment m = g eh s mc 2 Where g is the gyromagnetic ratio which relates the angular momentum to the intrinsic spin g=2 for charged, point-like, spin 1/2 particles. m g (e+e-, m+m-,t+t-) Hadrons g(neutron) = ≠ 0 Large deviations => quark substructure g(proton) = ≠ 2 Leptons Small deviations => coupling to virtual fields Deviations from g=2 are characterized by the Anomaly: a = g (a ~ .001 for a lepton) ICHEP Aug 16-22, 2004 Beijjing, China

3 ICHEP Aug 16-22, 2004 Beijjing, China
Coupling to X goes as mm2/mX2 factor of 40,000 compared to e Muon anomalous magnetic moment am(SM) = am(QED) + am(weak) + am(had) x 10-10 am(QED) = (.143) BNL E821 data ICHEP Aug 16-22, 2004 Beijjing, China

4 ICHEP Aug 16-22, 2004 Beijjing, China
Coupling to X goes as mm2/mX2 factor of 40,000 compared to e Muon anomalous magnetic moment am(SM) = am(QED) + am(weak) + am(had) x 10-10 am(QED) = (.143) + am(weak) = __ (.2) zo W m B field +3.89 BNL E821 data -1.94 (Higgs < 0.01) ICHEP Aug 16-22, 2004 Beijjing, China

5 ICHEP Aug 16-22, 2004 Beijjing, China
Coupling to X goes as mm2/mX2 factor of 40,000 compared to e Muon anomalous magnetic moment am(SM) = am(QED) + am(weak) + am(had) x 10-10 am(QED) = (.143) + am(weak) = __ (.2) + am(had1sto) = __ (7.2) + am(had h.o.) = __ (.6) BNL E821 data Requires Data ICHEP Aug 16-22, 2004 Beijjing, China

6 ICHEP Aug 16-22, 2004 Beijjing, China
Coupling to X goes as mm2/mX2 factor of 40,000 compared to e Muon anomalous magnetic moment am(SM) = am(QED) + am(weak) + am(had) x 10-10 am(QED) = (.143) + am(weak) = __ (.2) + am(had1sto) = __ (7.2) + am(had h.o.) = __ (.6) + am(hadl-by-l) = __ (2.5) BNL E821 data ICHEP Aug 16-22, 2004 Beijjing, China

7 ICHEP Aug 16-22, 2004 Beijjing, China
Coupling to X goes as mm2/mX2 factor of 40,000 compared to e Muon anomalous magnetic moment am(SM) = am(QED) + am(weak) + am(had) x 10-10 am(QED) = (.143) D am = any new physics + am(weak) = __ (.2) + am(had1sto) = __ (7.2) + am(had h.o.) = __ (.6) + am(hadl-by-l) = __ (2.5) BNL E821 data ICHEP Aug 16-22, 2004 Beijjing, China

8 How to Measure a Magnetic Moment
Brookhaven provides the pions from protons on nickel tgt Forward-going daughter muons are polarized m p nm ICHEP Aug 16-22, 2004 Beijjing, China

9 ICHEP Aug 16-22, 2004 Beijjing, China
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 mcg mcg wa = ws - wc = (g-2) eB 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 GeV/c ICHEP Aug 16-22, 2004 Beijjing, China

10 ICHEP Aug 16-22, 2004 Beijjing, China
WEAK-FOCUSSING MUON STORAGE RING B = 1.45 T Pm= GeV/c Rring = m Rstor = 4.5 cm Kicker Quad Quad Inflector 24 SciFi Calorimeters record 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 ICHEP Aug 16-22, 2004 Beijjing, China

11 ICHEP Aug 16-22, 2004 Beijjing, China
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: ( ) ppm Million evts per ns ICHEP Aug 16-22, 2004 Beijjing, China Fit for wa: No e-t/gt (1 + A cos (wat +j)) is no longer good enough.

12 ICHEP Aug 16-22, 2004 Beijjing, China
Main Disturbances m e Pileup of real pulses <5 ns apart 1% at earliest times: model and subtract Muon Losses bump beam and scrape (first 11 ms) scintillator paddles measure triples Rate dependent calorimeter response changes the effective Ethr in situ laser calibration system Bunched beam randomize 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 late time (no pileup) early + late early + late (corrected) Energy Spectrum ICHEP Aug 16-22, 2004 Beijjing, China

13 Consistency between analyzers checked
G2Too production Multi-parameter, Eth=1.5 GeV asymmetry-weighted, G2off production Multi-parameter quad corrections G2off production Multi-parameter G2off production 9-parameter ratio G2Too production 3 - parameter ratio with cancellation Low n (black), high n (clear), combined (red) data sets. ICHEP Aug 16-22, 2004 Beijjing, China

14 Measuring the Magnetic Field
0.5 ppm contours are 750 nT over an average field of Tesla. muon sees the field averaged over azimuth vertical distance (cm) 17 calibrated NMR probes inside the trolley measure the field every cm horizontal distance (cm) ICHEP Aug 16-22, 2004 Beijjing, China

15 ICHEP Aug 16-22, 2004 Beijjing, China
Blind Analysis Decay positrons NMR wa = am e B mp B = h wp mc am = R l + R where R = wa / wp is measured by E821 and l = mm / mp from 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. ICHEP Aug 16-22, 2004 Beijjing, China

16 ICHEP Aug 16-22, 2004 Beijjing, China
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 World average am = (6) x 10-10 Recall am = R/(l-R) where we measure R = wa/wp and where l = mm/mp = (10) Quote CPT results in terms of DR = ( ) x 10-6 ICHEP Aug 16-22, 2004 Beijjing, China

17 ICHEP Aug 16-22, 2004 Beijjing, China
Taking Dam = am(exp)-am(thry): the details are still changing… QED (.12) loop: Laporta & Remiddi + Kinoshita & Nio update up from (.29) EW LO st order e.g. Fujikawa, Lee, Sanda ’72 EW HO (2) loop, NL+LL Czarnecki, Krause, Marciano ‘ updated: Czarnecki, Marciano, Vainshtein ’ (.2) agrees with 15.3 (.2) Knecht, Peris, Perrottet, DeRafael Had LO (e+e-) (6.2)(3.6) Davier,Eidelman, Hoecker, Zhang hep-ph/ v (5.9)(2.4) Hagiwara, Martin, Nomura, Teubner hep-ph/ add KLOE (5.6)(3.6) Davier, Hoecker, Eidelman, Zhang ICHEP04 add QCD (5.3)(3.5) Had NL (.1) Hagiwara, Martin, Nomura, Teubner agrees with (.6) Krause ’97 Had l-by-l (2.5) Melnikov & Vainstein hep-ph/ up from 8.0 (4.0) Nyffler ’02 World Avg (moving target) D am = (9.2) x s using the latest – See Hoecker’s talk this afternoon… ICHEP Aug 16-22, 2004 Beijjing, China

18 ICHEP Aug 16-22, 2004 Beijjing, China
Improvement in Theory will continue over the next decade Precision in the dispersion integral CMD-2 (e+e- at ) 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) ICHEP Aug 16-22, 2004 Beijjing, China

19 ICHEP Aug 16-22, 2004 Beijjing, China
New KLOE data using “radiative return” method Initial State Radiation lowers 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 ICHEP Aug 16-22, 2004 Beijjing, China

20 Evolution of the Experimental Uncertainties
Data Set: p-injection kicker installed st long run new inflector reverse polarity field stabilized 12 M e M e B e B e B e- Statistics (Ne above Ethr) ppm ppm ppm ppm ppm Systematics ppm ppm ppm ppm ppm dwa ppm ppm ppm ppm ppm Dominated by WFD threshold pileup pileup coherent betatron gain stability pion flash AGS mistune AGS mistune m loss, pileup m loss dwp ppm ppm ppm ppm ppm Dominated by thermal fluctuations trolley position trolley position trolley position trolley position no active feedback inflector inflector Still statistics dominated! ICHEP Aug 16-22, 2004 Beijjing, China

21 ICHEP Aug 16-22, 2004 Beijjing, China
Proposal P969 for another Run at BNL Improve am by a factor of 2.5 to match expected theory improvement 500 hrs setup (pulse-on-demand) hrs dedicated 5 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 and no accompanying pions to create “flash” Store More Muons Open-end inflector design + 2nd 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 ICHEP Aug 16-22, 2004 Beijjing, China

22 Evolution of the Experimental Uncertainties
Data Set: 1st long run new inflector reverse polarity improved BNL (20 week run) 1 B e B e B e B e+ Statistics (Ne above Ethr) ppm ppm ppm ppm Systematics ppm ppm ppm ppm dwa ppm ppm ppm ppm Dominated by pileup coherent betatron gain stability AGS mistune m loss, pileup m loss, pileup dwp ppm ppm ppm ppm Dominated by trolley position trolley position trolley position trolley position inflector ICHEP Aug 16-22, 2004 Beijjing, China

23 ICHEP Aug 16-22, 2004 Beijjing, China
In CMSSM, am can be combined with b sg, cosmological relic density Wh2, and LEP Higgs searches to constrain c mass Da = 24 x favors higher tan b and avoids coannihilation region From Keith Olive using 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 = Excluded for neutral dark matter ICHEP Aug 16-22, 2004 Beijjing, China

24 ICHEP Aug 16-22, 2004 Beijjing, China
The CMSSM plot with error on Dam of 4.6 x (assuming better theory and a new BNL g-2 experiment) Dam=24(4.6) x (discrepancy at 6 s) Dam = 0 (4.6) x 10-10 Current Discrepancy Standard Model ICHEP Aug 16-22, 2004 Beijjing, China

25 ICHEP Aug 16-22, 2004 Beijjing, China
How would a non-zero electric dipole moment affect g-2? ICHEP Aug 16-22, 2004 Beijjing, China

26 ICHEP Aug 16-22, 2004 Beijjing, China
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. ICHEP Aug 16-22, 2004 Beijjing, China

27 ICHEP Aug 16-22, 2004 Beijjing, China
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 d m+ < 2.8 x e-cm (95% C.L.) using 2000 data & FSDs (McNabb et al, hep-ex/ ) Precise lifetime G ICHEP Aug 16-22, 2004 Beijjing, China

28 ICHEP Aug 16-22, 2004 Beijjing, China
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… ICHEP Aug 16-22, 2004 Beijjing, China

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