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Measurement of the muon anomaly to high and even higher precision

Measurement of the muon anomaly to high and even higher precision. David Hertzog* University of Illinois at Urbana-Champaign.

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Measurement of the muon anomaly to high and even higher precision

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  1. Measurement of the muon anomaly to high and even higher precision David Hertzog* University of Illinois at Urbana-Champaign * Representing the E821 Collaboration: Boston, BNL, Budker Inst., Cornell, KFI, Heidelberg, Illinois, KEK, Minnesota, Tokyo Tech, Yale& new E969groups: JMU, Kentucky, LBL/UC-Berkeley

  2. OutlineThe muon is a little brother of the tau • The “old” BNL experiment • With the 2004 result on m- • The theoretical ingredients and overall motivation • Lots will follow today by the real experts • The “new” experiment – 0.2 ppm is the new goal • Some fresh new ideas and bold ambition • Approved this week at BNL with Highest “Must Do” Status

  3. B Muon g-2 is determined from 3 measurements (1) Precession frequency (2) Muon distribution (3) Magnetic field map

  4. And, 4 miracles make it happen • Polarized muons n p+ m+

  5. Muons are created from in-flight p decay and enter ring in a bunch

  6. And, 4 miracles make it happen • Polarized muons • Precession proportional to (g-2) n p+ m+ µ

  7. e Momentum Spin The muon spin precesses faster than the cyclotron frequency:amis proportional to the difference frequency

  8. And, 4 miracles make it happen • Polarized muons • Precession proportional to (g-2) • Pm The magic momentum E field doesn’t affect muon spin when g = 29.3 n p+ m+ µ

  9. 100 kV KICK 0 500 ns incoming muons Quads BNL Storage Ring Only a few percent get stored!

  10. 2001 1 ppm contours 0.05 0.09 0.05 0.07 0.10 0.17 Magnetic Field Measured in situ using an NMR trolley Continuously monitored using 150 fixed probes mounted above and below the storage region

  11. And, 4 miracles make it happen • Polarized muons • Precession proportional to (g-2) • Pm The magic momentum E field doesn’t affect muon spin when g = 29.3 • Parity violation in the decay n p+ m+ µ

  12. 2.5 ns samples Counts TIME Measuring the difference frequency “wa” e+ < 20 ps shifts < 0.1% gain change

  13. Fit to Simple 5-Par Function N(t) = N0e-t/t[1+Acos(wat + f)] Few billion events Getting a good c2is a challenge

  14. In 2001, we adjusted the ring index to avoid overlap Fourier Spectrum of Residuals to 5-par Fit fg-2 ≈229 KHz fCBO≈466 KHz

  15. “Breathes” (smaller effect) Detector Coherent Betatron Oscillations Beam into storage volume Detector “Swims” Inflector mappingto storage volume Acceptance vs average radius Acceptance Radius

  16. Modulation of N0, A, f with fcbo

  17. Pileup Subtraction Phase shift possible Separate when you can ... Extrapolate to zero deadtime on average using out-of-time resolved events Build pileup-free histogram with deadtime low rate deadtime corrected Energy of positrons

  18. m Excess loss rate muon decay Do these muons have a different phase ? Constant loss rate Uncertainty, mostly due to protons Muon Loss & Stored Protons hit hit hit Account for “slow effects” by correction of muon flux in ring beyond exponential decay

  19. Internal Consistency: Chi-Sq, Run # Normalized c2 vs. Start Time of Fit Precession Frequency vs. Run Number

  20. Internal Consistency: Start Time, Detector, Energy Precession Frequency vs. Fit Start Time Precession Frequency vs. Energy Band Precession Frequency vs. Detector #

  21. Five complementary analyses of wa G2Too productionMulti-parameter, Eth=1.5 GeV asymmetry-weighted, G2off productionMulti-parameter quad corrections G2off productionMulti-parameter G2off production9-parameter ratio G2Too production3 - parameter ratio with cancellation Low n (black), high n (clear), combined (red) data sets.

  22. am = 11659214.0(8)(3)  10-10(0.7 ppm) - The new result is in excellent agreement with previous measurements on m+ g-2 Collaboration: PRL 92 161802 (2004)

  23. g ≠ 2 because of virtual loops, many of which can be calculated very precisely p g m Z m p B Weak Had LbL Had VP QED Many of the next 8! talks will discuss the standard model theory

  24. h µ  - h Hadronic vacuum polarization is obtained from e+e- and/or tau data e+  is related to and also h e-

  25. The t - e+e- comparison Difference is significant AND energy dependent Davier, et al hep-ex/00308214 Jan 04

  26. Pion Formfactor 45 45 CMD-2 KLOE 40 35 30 And, from ICHEP, A. Hocker is stepping back from the Tau result until isospin issues are fully understood: 25 0.4 0.5 0.6 0.7 0.8 0.9 20 15 10 5 0 sp [GeV2] Today, we’ll hear about the latest KLOE “confirmation” of CMD2 From G. Venanzone

  27. am(worldavg)= 11 659 208(6)  10-10(0.5 ppm) Comparison of final results and theory Includes new HLbL shift and KLOE result D(ee) =25±9 ± Opps Opps2 KLOE Divorce! ee-t marriage

  28. Discrepancy with e+e- based theory • What might this mean? • New physics or a fluctuation

  29. µ µ µ W W B Non-zeroDam appeals to a catalog ofSM Extensions Sensitive for supergravity grand unification, especially for large tan  Chargino-Sneutrino Neutralino-Smuon • New physics … • SUSY • Leptoquarks • Muon substructure • Anomalous W couplings 100 tan b = 10 50 ee-expt amSUSY[10-10] tau-expt 0 -50 100 300 500 700 900 smuon mass (GeV)

  30. In CMSSM, am can be combined with b→sg, cosmological relic density Wh2, and LEP Higgs searches to constrain c mass tanb=10 Excluded by direct searches Allowed 2s band am(exp)– am(e+e- thy) Preferred Excluded for neutral dark matter Courtesy K.Olivebased on Ellis, Olive, Santoso, Spanos

  31. Two “futures” when new experiment and improved theory are complete Dam  25(5) x 10-10 (5s) Dam0 (5) x 10-10 Same DiscrepancyStandard Model

  32. E969 is a new g-2 experiment at BNLStrategy is basic: • Get more muons – E821 was statistics limited (sstat = 0.46 ppm, ssyst = 0.3 ppm) • AGS 20% more protons • Backward-decay beam • Higher-transmission beamline • New, open-end inflector • Upgrade detectors, electronics, DAQ • Reduce dB, systematic uncertainty on magnetic field, B • Improve calibration, field monitoring and measurement • Reduce dwa systematic uncertainty on precession, ωa • Improve the electronics and detectors • New parallel “integration” method of analysis • Keep the main ideas and ring Expect 5 x more rate

  33. Near side Far side Pedestal vs. Time E821 used forward decay beam, which permitted a large p component to enter ring Pions @ 3.115 GeV/c Decay muons @ 3.094 GeV/c This baseline limits how early we can fit data

  34. Expect for both sides New experiment uses a backward decay beam with large mismatch in p/m momentum at final slits Pions @ 5.32 GeV/c Decay muons @ 3.094 GeV/c No hadron-induced prompt flash Approximately the same muon flux is realized x 1 more muons

  35. Decay region will include more quads to capture muons E821 lattice Lattice doubled x 2 more muons

  36. Improved transmission into the ring Inflectoraperture Inflector Storage ring aperture E821 Closed End P969 Proposed Open End x 2 more muons Outscatters muons

  37. Systematic Error Evolution by Factor of 2 • Field improvements will involve 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

  38. T Method Q Method E969: Precession Measurement • Expect 5 x more rate • Segment calorimeters • 500 MHz waveform digitization • Greatly increased data volume for DAQ • Introduce parallel “Q” method of data collection and analysis • Integrate energy flow vs. time

  39. Starting ideas for new, fast, dense and segmented W-SciFi calorimeters • 20-fold segmentation • 0.7 cm X0 • 14%/Sqrt(E) • Greatly constrained space

  40. Conclusions • E821 was very successful, reaching 0.5 ppm final uncertainty • Theory has gone from  5 ppm →0.6 ppm during same time period • Today’s status: tantalizing 2.7s discrepancy • Next phase includes new, approved experiment and continued work on hadronic issues related to theory • KLOE, BaBar, Belle, radiative corrections, lattice, … • Together, expect reduction in expt-thy comparison by x 2 hertzog@uiuc.edu

  41. Extra Slides Follow

  42. * higher multipoles, trolley voltage and temperature response, kicker eddy currents, and time-varying stray fields. Field Uncertainties - History

  43. Systematic errors on ωa (ppm) Σ* = 0.11

  44. The t - decay input to H-VP  • Data precise • Related by CVC with corrections • Isospin asymmetry (p+p-vs p0p-) W- - p0 p- • Issues with r0 - r- mass and width raised last year • Long-distance radiative corrections • Bottom line, can the t data contribute in the long run at sub % level?

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