Muon g-2: Where have all the muons gone?

1. Muon g-2:Where have all the muons gone? David Hertzog Bunce Symposium Gerry Collaboration: Boston, BNL, Budker, Cornell, Heidelberg, Illinois, KVI, KEK, Minnesota, Tokyo, Yale

2. Outline • g-2 impact today • How is g-2 measured? • Gerry and g-2 • The Future BuNce 2008

3. g-2 impact today Chapter I

4. Particle Physicists Ask Why spin? • Why matter? • CP Violation • Why mass? • Higgs field • Why this standard model? • SUSY or other extensions

5. Indirect evidence for New Physics from thePrecision Frontier Muon Storage Ring at BNL

6. Standard Model BNL Expt. g-2 experiment / theory comparison • Key points: • Theory: 0.48 ppm • Experimental 0.54 ppm (statistics limited!) • Dam(expt-thy) = (297±88) x 10-11 (3.4 s) deRafael, Glasgow MDM Arguably, strongest experimental evidence of Physics Beyond Standard Model

7. In 2001, the muon was in the news… Time called the muon “a winner !”

8. Compare to Theory “I will spare you the long, checkered, sometimes amusing history of the theory here, with it’s sign flips, and “gotcha” corrections, and them there radiative corrections, and hard-to-figure-out loops with those pions and other stuff that goes on kinda’ quick when you aren’t really looking to see if it’s so and such …” (S.P.) “Look you guys, put the damn number on the table !” T. Kirk (BNL) New York Times, August, 2002 Just tell the theorists:

9. p p g m Z m p p B Good shape Not so good shape Weak Had LbL Had VP Had VP QED 2006 plot KEY REGION g ≠ 2 because of virtual loops, many of which can be calculated very precisely A significant amount has happened in 2008 … some confirming … some unnerving

10. g m Z m p p p p B Weak Had LbL Had LbL QED Had VP Had VP Hadronic light-by-light is settling down (finally) This is new, based on combined work by three leading groups

11. New physics enters through loops … e.g., SUSY R-parity conserving Supersymmetry (vertices have pairs) And the diagrams are amplified by powers of tanb(here linearly)

12. Typical CMSSM 2D space showing g-2 effectHere and in next slides, we also project a reduced uncertainty on expt/thy from 88 to 39 in 10-11 units based on a next-generation expt. Present: Dam = 297 ± 88 x 10-11 Future Dam = 297 ± 39 x 10-11 scalar mass 2s 1s Excluded for neutral dark matter gaugino mass With new experimental and theoretical precision and same Dam This CMSSM calculation: Ellis, Olive, Santoso, Spanos. Plot update: K. Olive

13. Expt The Snowmass Points and Slopes give reasonable benchmarks to test observables with model predictionsMuon g-2 is a powerful discriminatorno matter where the final value lands!! Future? Model Version

14. Suppose the MSSM reference point SPS1a* is realized and parameters determined by global fit (from LHC results) • sgn(m) can’t be obtained from the collider • tanbcan’t be pinned down by collider Possible future “blue band” plot, where tan β is determined from aμ. D. Stockinger * SPS1a is a ``Typical '' mSUGRA point with intermediate tanb = 10 *Snowmass Points and Slopes: http://www.ippp.dur.ac.uk/~georg/sps/sps.html

15. How is g-2 measured ? Chapter II

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

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

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

19. 1997: First evidence that muons are stored! Matthias has found the electrons ! 149 ns

20. Far Side Near Side A tough reality and delicate balancing act E821 used forward decay beam, which permitted a large p component to enter ring DP ~ 1.7% Pions @ 3.115 GeV/c Decay muons @ 3.094 GeV/c

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

22. e Momentum Spin amis proportional to the difference between the spin precession and the rotation rate

23. 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

24. 100 kV KICK 0 500 ns incoming muons Quads BNL Storage Ring Only a few percent get stored!

25. 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

26. 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

27. 2.5 ns samples Counts TIME Measuring the difference frequency “wa” e+ < 20 ps shifts < 0.1% gain change

28. 1st Plot showing muon precession signal … the “money” plot But, Gerry got all of us who were awake then to sign it too Plot made by Prisca Cushman

29. Components do not pull g-2 Data can “almost” be fit using a simple 5-parameter function N(t) = N0e-t/t[1+Acos(wat + f)] Few billion events Getting a good c2requires understanding beam motions

30. A double-blind analysis culture Magnetic Field Secret Offsets Secret Offsets UIUC UIUC Data Production BU Yale (Each year had different divisions of labor)

31. E821 Complete and Published 14 Individual analyses independent and consistent Bennett et al, PRD 73, 072003 (2006)

32. Where have all the muons gone?* • Where have all the protons gone? • Gone to pions, every one … • Where have all the pions gone? • Gone to muons, every one … • Where have all the muons gone? • Gone to electrons, every one … • Where have all the spokesmen gone? • Gone to coffee, every one … The “Gang of Four” *Apologies to Pete Seeger. The complete set of our lyrics, once sung on Gerry’s deck at a pool party, remain locked unto the year 2050

33. Gerry and g-2 Chapter III

34. S Gerry Bunce, Bill Morse, Vernon Hughes, Gordon Danby + hosts of others • The rings have great power • The rings can consume you • The rings will corrupt you

35. Gerry, a respected counting house leader … Gerry, like MacArthur, has returned !! Now we will stabilize our beam and Gotham will be safe once again … (Ofer, 1997)

36. A Proud Papa

37. Lots of highly cited papers Gerry got us all to sign this too

38. Toys’ for Grown Boys

39. Gerry’s World Secret passage way into the castle g-2 Quiz: Name that part

40. Gerry: Casting the Golden Ring

41. …while building the ring …

42. The Future g-2FiNALe Goal: 0.14 ppm; 21 x statistics Move ring to FNAL Chapter IV

43. Then, to accept the higher rate, changes in the experiment are required; e.g., 4 Segmented detectors For BNL E969, we identified some obvious places to improve the muon transmission and to prepare for higher rate Open inflector 2 1 Beamline changes 3 Improve kicker

44. Gives 18 Hz of ring fills BNL was 4.4 Hz Intensity being studied, but expect 1year run will achieve the x21 statistics goal Most items are costed Including moving the ring Goal is < $20 M Target area least understood The g-2FiNALe “next-generation” experiment aiming at >4x improved precision

45. pbar target 8 GeV/c protons not 120 GeV as is now s(p) & 3.1 GeV/c Not 24 GeV (~3 lower) Li lens Pion to muon decay line optics New building required for ring Use pbar complex as an 800 m long “dogbone” beamline

46. Who will be the new Gerry ? Key Question

47. Final Thought from the Lord(s) of the Ring(s) • to store muons • to observe positrons • to connect muons to new physics quantum loops One Ring to rule them all, One Ring to find them, One Ring to bring them all and in the darkness bind them THANKS GERRY !!!!!

48. The End !

49. “Muon Anomalous Magnetic Moment—The Last Word”Robert W. WilliamsNew Frontiers in High-Energy Physics, 1978 “I conclude that a super effort might lead to a determination of am to between 1 and 2 parts per million …” “It is the end of an era; the muon g-2 worker is no longer a Kit Carson blazing a trail in the wilderness, but more like a J. Edgar Hoover keeping a watchful eye on the imaginative excesses of theorists.”