Priscilla Cushman University of Minnesota ICHEP Aug 16-22, 2004 Beijjing, China 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 Does g-2 point to new physics?: Current Status and Future Plans

Priscilla Cushman University of Minnesota ICHEP Aug 16-22, 2004 Beijjing, China Deviations from g=2 are characterized by the Anomaly: ( a = g-2 (a  ~.001 for a lepton) 2  = g eh s 2mc 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.    (e + e ,            Hadrons Hadrons g(neutron) = ≠ 0 Large deviations => quark substructure g(proton) = ≠ 2 Leptons Leptons Small deviations => coupling to virtual fields The Magnetic Moment

Priscilla Cushman University of Minnesota ICHEP Aug 16-22, 2004 Beijjing, China a   QED  = (.143) Muon anomalous magnetic moment Coupling to X goes as m  2 /m X 2 factor of 40,000 compared to e a  (SM) = a   QED  + a  (weak) + a  (had) BNL E821 data x

Priscilla Cushman University of Minnesota ICHEP Aug 16-22, 2004 Beijjing, China + a   weak  = 15.4__ (.2) a   QED  = (.143) Muon anomalous magnetic moment Coupling to X goes as m  2 /m X 2 factor of 40,000 compared to e a  (SM) = a   QED  + a  (weak) + a  (had) BNL E821 data µ µ zozo µ µ WW  B field x (Higgs < 0.01)

Priscilla Cushman University of Minnesota ICHEP Aug 16-22, 2004 Beijjing, China + a   weak  = 15.4__ (.2) + a   had1 st o  = 696.3__ (7.2) + a   had h.o.  = -10.0__ (.6) a   QED  = (.143) Muon anomalous magnetic moment Coupling to X goes as m  2 /m X 2 factor of 40,000 compared to e a  (SM) = a   QED  + a  (weak) + a  (had) Requires Data BNL E821 data x

Priscilla Cushman University of Minnesota ICHEP Aug 16-22, 2004 Beijjing, China + a   weak  = 15.4__ (.2) + a   had1 st o  = 696.3__ (7.2) + a   had h.o.  = -10.0__ (.6) + a   hadl-by-l  = __ (2.5) a   QED  = (.143) Muon anomalous magnetic moment Coupling to X goes as m  2 /m X 2 factor of 40,000 compared to e a  (SM) = a   QED  + a  (weak) + a  (had) BNL E821 data x

Priscilla Cushman University of Minnesota ICHEP Aug 16-22, 2004 Beijjing, China + a   weak  = 15.4__ (.2) + a   had1 st o  = 696.3__ (7.2) + a   had h.o.  = -10.0__ (.6) + a   hadl-by-l  = __ (2.5) a   QED  = (.143) Muon anomalous magnetic moment Coupling to X goes as m  2 /m X 2 factor of 40,000 compared to e a  (SM) = a   QED  + a  (weak) + a  (had)  a  = any new physics BNL E821 data x

Priscilla Cushman University of Minnesota ICHEP Aug 16-22, 2004 Beijjing, China Brookhaven provides the pions from protons on nickel tgt Forward-going daughter muons are polarized       0 How to Measure a Magnetic Moment

Priscilla Cushman University of Minnesota ICHEP Aug 16-22, 2004 Beijjing, China How to Measure a Magnetic Moment  s = 1+  (g-2) eB and  c = eB 2 mc  mc   a =  s -  c = (g-2) eB 2 mc  c (T c = 149 ns)  a =  s -  c (precesses ~12 0 per cycle) Which vanishes at the “magic momentum” of GeV/c (a   - )  x E (a   - )  x E emc 1   -1 Quadrupole E field gives additional term in  a :+

Priscilla Cushman University of Minnesota ICHEP Aug 16-22, 2004 Beijjing, China Kicker Quad Inflector Quad WEAK-FOCUSSING MUON STORAGE RING B = 1.45 T P  = GeV/c R ring = m R stor = 4.5 cm 24 SciFi Calorimeters record time and energy of decay e+ (or e-) Calorimeters select high energy e’s These e’s are preferentially emitted in the direction of the  spin  e    e 

Priscilla Cushman University of Minnesota ICHEP Aug 16-22, 2004 Beijjing, China Fit for  a : N o e -t/  (1 + A cos (  a t  is no longer good enough. Million evts per ns Fit for   radial distribution,  xE correction: ( ) ppm Cyclotron Frequency at early times 2001 data set: 4 billion e+ (E > 1.8 GeV, t > 32 ms after injection) g-2 Precession Frequency after debunching

Priscilla Cushman University of Minnesota ICHEP Aug 16-22, 2004 Beijjing, China Main Disturbances Pileup of real pulses <5 ns apart 1% at earliest times: model and subtract Muon Losses bump beam and scrape (first 11  s) scintillator paddles measure triples Rate dependent calorimeter response changes the effective E thr in situ laser calibration system Bunched beam randomize time spectrum in bins of T cyclotron Coherent Betatron Oscillations image of the inflector exit moves around the ring as a beat frequency of w c and w  fiber harp and traceback chamber measure stored muon profile vs time late time (no pileup) early + late early + late (corrected) Energy Spectrum  e

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

Priscilla Cushman University of Minnesota ICHEP Aug 16-22, 2004 Beijjing, China 17 calibrated NMR probes inside the trolley measure the field every cm vertical distance (cm) horizontal distance (cm) muon sees the field averaged over azimuth ppm contours are 750 nT over an average field of 1.45 Tesla. Measuring the Magnetic Field

Priscilla Cushman University of Minnesota ICHEP Aug 16-22, 2004 Beijjing, China Blind Analysis Decay positrons NMR  a = a  e B  p  h  p mc a  = R + R where R =  a  p is measured by E821 and =    p  from muonium hyperfine structure Offline Team (5 analyses) Magnet Team (2 analyses)  a  p Both  ’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.

Priscilla Cushman University of Minnesota ICHEP Aug 16-22, 2004 Beijjing, China a  x World average a  = (6) x Recall a  = R/( -R) where we measure R =  a /  p and where =   /  p = (10) Quote CPT results in terms of  R = ( ) x Results from the 2000/2001 datasets & World Average In order to use the  -decay data, you need CVC – its not perfect. Isospin violation - include  mass differences? Experimental problems - normalization?

Priscilla Cushman University of Minnesota ICHEP Aug 16-22, 2004 Beijjing, China Taking  a  = a  (exp)-a  (thry): the details are still changing… QED (.12) 5-loop: Laporta & Remiddi + Kinoshita & Nio update up from (.29) EW LO st order e.g. Fujikawa, Lee, Sanda ’72 EW HO -4.07(2) 2-loop, NL+LL Czarnecki, Krause, Marciano ‘96 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 -9.8 (.1) Hagiwara, Martin, Nomura, Teubner agrees with (.6) Krause ’97 Had l-by-l 13.6 (2.5) Melnikov & Vainstein hep-ph/ up from 8.0 (4.0) Nyffler ’02 World Avg (moving target)  a  = 25.2 (9.2) x   using the latest – See Hoecker’s talk this morning…

Priscilla Cushman University of Minnesota ICHEP Aug 16-22, 2004 Beijjing, China Improvement in Theory will continue over the next decade 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 a  (had VP from e+e-)  0.3 ppm Other Avenues Further understanding  vs e+e- discrepancy (Belle, Cleo2) Improvements in hadronic light-by-light term Lattice gauge calculations 0.6% 0.1% (2010) Precision in the dispersion integral

Priscilla Cushman University of Minnesota 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-   +  - directly since photon is hard

Priscilla Cushman University of Minnesota ICHEP Aug 16-22, 2004 Beijjing, China Evolution of the Experimental Uncertainties Data Set:  -injection kicker installed 1 st long run new inflector reverse polarity field stabilized 12 M e + 84 M e + 1 B e + 4 B e + 4 B e - Statistics (N e above E thr ) 12.5 ppm 4.9 ppm 1.25 ppm 0.6 ppm 0.7 ppm Systematics 2.9 ppm 1 ppm 0.5 ppm 0.4 ppm 0.3 ppm  a 2.6 ppm 0.7 ppm 0.3 ppm 0.3 ppm 0.21 ppm Dominated by WFD threshold pileup pileup coherent betatron gain stability pion flash AGS mistune AGS mistune  loss, pileup  loss  p 1.3 ppm 0.5 ppm 0.4 ppm 0.24 ppm 0.17 ppm Dominated by thermal fluctuations trolley position trolley position trolley position trolley position no active feedback inflector inflector Still statistics dominated!

Priscilla Cushman University of Minnesota ICHEP Aug 16-22, 2004 Beijjing, China Double number of beamline quads + use backward-going muons Flux x 2.1 and no accompanying pions to create “flash” Provide More Muons Proposal P969 for another Run at BNL Improve a  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 Open-end inflector design + 4th muon kicker  ’s x 2 and reduced systematics from Coherent Betatron Oscillation Store More Muons Handle Higher rates Improve B-field Measurement Increased Calorimeter Segmentation Continuous WFD, Commercial MTDC’s, IIncrease DAQ throughput In situ measurements of field changes with kicker eddy current Trolley position calibration and mapped NMR positions

Priscilla Cushman University of Minnesota ICHEP Aug 16-22, 2004 Beijjing, China Evolution of the Experimental Uncertainties Data Set: st long run new inflector reverse polarity improved BNL (20 week run) 1 B e + 4 B e + 4 B e - 70 B e+ Statistics (N e above E thr ) 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  a 0.3 ppm 0.3 ppm 0.21 ppm 0.11 ppm Dominated by pileup coherent betatron gain stability AGS mistune  loss, pileup  loss, pileup  p 0.4 ppm 0.24 ppm 0.17 ppm 0.11 ppm Dominated by trolley position trolley position trolley position trolley position inflector

Priscilla Cushman University of Minnesota ICHEP Aug 16-22, 2004 Beijjing, China From Keith Olive using the g-2 PRL (2003)  a  and the method described in Ellis, Olive, Santoso, Spanos In CMSSM, a  can be combined with b s , cosmological relic density  h 2, and LEP Higgs searches to constrain  mass  a = 24 x favors higher tan  and  avoids coannihilation region Allowed  band a  (exp) – a  (e+e- thy) Excluded by direct searches Excluded for neutral dark matter cosmologically preferred region  h 2 =

Priscilla Cushman University of Minnesota ICHEP Aug 16-22, 2004 Beijjing, China Current Discrepancy Standard Model The CMSSM plot with error on  a  of 4.6 x (assuming better theory and a new BNL g-2 experiment)  a  =24(4.6) x (discrepancy at 6   a   0 (4.6) x

Priscilla Cushman University of Minnesota ICHEP Aug 16-22, 2004 Beijjing, China How would a non-zero electric dipole moment affect g-2?

Priscilla Cushman University of Minnesota ICHEP Aug 16-22, 2004 Beijjing, China 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 Access to the vertical oscillation comes from auxiliary detectors listed in order of segmentation: For example, a fit to the average y-position in the FSD vs time yields the amplitude of the “out- of-phase” component.

Priscilla Cushman University of Minnesota ICHEP Aug 16-22, 2004 Beijjing, China Look for an edm paper in the next couple months Reduced the limit on edm by ~ x4 Reduced potential effect on  a by ~ x16 Also work is proceeding on Edm of  - (2001 data with PSD – improve another x2) Combine with  to get best  - lifetime (20 ppm) Comparison of  + vs  - lifetime Limit on sidereal variation Data analysis on the 2000 & 2001 runs continues d   + < 2.8 x e-cm (95% C.L.) using 2000 data & FSDs (McNabb et al, hep-ex/ ) Precise lifetime  G

Priscilla Cushman University of Minnesota ICHEP Aug 16-22, 2004 Beijjing, ChinaConclusions Things are getting exciting One can reasonably hope to reduce the error on  a  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…