1. Low Energy Tests of the Standard Model Emlyn Hughes Spin 2004 Trieste October 14, 2004 *PAST *PRESENT *FUTURE

2. Electroweak Mixing Angle e = g sin  w Characterizes the mixing between the weak and EM interaction in the electroweak theory sin 2  w = 1 - MwMw MzMz 2 2

3. 3 Types of Measurements *Electron scattering (parity violation) *Atomic parity violation *Neutrino physics (NC/CC cross section)

4. Parity Violation in Polarized Electron Scattering e-   unpolarized quarks or electrons or protons Parity conserving Parity violating

5. Parity Violation in the Electroweak Theory A PV  2A W A EM AWAW A EM + 22 ~ A W A EM ~ 2 g2g2 mZmZ 2 + q 2 e2e2 q2q2 2 A PV ~ q2q2 mZmZ 2 2 A PV =  -   +  RL RL

6. SLAC

7. End Station A

8. SLAC Parity Experiments e- Target (unpolarized) High Energy Detector A PV =  -   +  Parity-violating asymmetry RL RL

9. SLAC E80

10. Yale E80 Polarized Source

11. SLAC End Station A

12. SLAC E95

13. Results on Parity Violation A LR < 5 x 10 -3 at Q 2 ~ 1.4, 2.7 GeV 2 E80 E95 A LR < 3.2 x 10 -3 at Q 2 ~ 4 GeV 2 Not sensitive to electroweak mixing in the Standard Model

14. First Measurements of Electroweak Mixing

15. SLAC E122

16. Detector e 16 – 22 GeV Liquid Deuterium GaAs source High current 30 cm target Dedicated run

17. Reversed every few runs 120 Hz

18. SLAC E122 waveplate reversal

19. Parity-violating asymmetry SLAC E122 waveplate reversal

20. SLAC E122 Energy Scan Parity-violating asymmetry

21. SLAC E122 Result sin 2  w = 0.224 + 0.020 First definitive measurement of mixing between the weak and electromagnetic interaction (1978)

22. Atomic Parity Violation e- A LR ~ m e  22 mZmZ 2 ~ 10 -14  or Z p q2q2 mZmZ 2 ~22

23. Experiment Z 3 Law Heavy Atoms Theory PV Signal sin 2  w Bismuth Z = 83

24. Atomic Parity Violation Bismuth

25. Atomic Parity Violation Bismuth

26. Atomic Parity Violation Bismuth

27. Atomic Parity Violation Bismuth E122

28. Gargamelle Neutrino Physics Bubble Chamber

29. HPWF Neutrino Detector (Harvard, Pennsylvania, Wisconsin, Fermilab)

30. 1974

32. 1978

33. (1975) (1977) 1978

34. LEP and SLC e + e - collider  sin 2  w = 0.00016 (PDG2004)from Z pole measurements TODAY...

35. Q (GeV) sin 2  w Status in 1999 ~5%

36. SLAC Experiment E158 Detector e 50 GeV Liquid Hydrogen A PV =  -   +  Without electroweak radiative corrections, In practice: A PV ~1.5 x 10 -7 2  (3 + cos  ) 2 2 16 sin  2 A PV = 1 4  sin 2  w () m E G F e-e- scattering

37. UC Berkeley Caltech Jefferson Lab Princeton Saclay SLAC Smith College Syracuse UMass Virginia 7 Ph.D. Students 60 physicists Sept 97: EPAC approval 1998-99: Design and Beam Tests 2000: Funding and construction 2001: Engineering run 2002: Physics Runs 1 (Spring), 2 (Fall) 2003: Physics Run 3 (Summer) E158 Collaboration

38. Scattering Processes e-   Parity-conserving Parity-violating e-  p p  Background

39. Challenges I. Statistics II. Beam monitoring & resolution III.Beam systematics IV.Backgrounds  jitter vs. statistics  false asymmetries

40. Spectrometer magnets Concrete shielding target Detector cart Setup in End Station A

43. STATISTICS # electrons per pulse10 7 Rep rate (120 Hz)10 9 Seconds/day10 14 100 days10 16  A ~ 10 -8

44. II. BEAM MONITORING

45. Agreement (MeV)  toroid  30 ppm  BPM  2 microns  energy  1 MeV BPM24 X (MeV) BPM12 X (MeV) Resolution 1.05 MeV Beam Monitoring Correlations

47. III. Beam Asymmetries Polarized source

48. SLOW REVERSALS *Halfwaveplate @ source ~few hours *48 vs. 45 GeV energy ~ few days

49. A PV vs. time ppb

50. Asymmetry Results

51. IV. BACKGROUNDS *electron-proton elastic scattering *pion production *radiative inelastic electron-proton scattering W 2 > 3 GeV 2 *2 photon events with transverse polarization ******

52. ep Detector Asymmetry

53. Transversely Polarized Beam

54. Run 1: Spring 2002 Run 2: Fall 2002 Run 3: Summer 2003 E158 Physics Runs

55. A PV =  175  30 (stat)  20 (syst) ppb sin 2  = 0.2293 ± 0.0024 (stat) ±0.0016 (syst) At Q 2 = 0.027 (GeV/c) 2 …. w RUN I FINAL RESULT MS sin 2  = 0.2311 ± 0.00016 w MS Theory:

56. Run I

57. A PV =  128  14 (stat)  12 (syst) ppb sin 2  = 0.2330 ± 0.0011 (stat) ±0.0010 (syst) At Q 2 = 0.027 (GeV/c) 2 …. w All E158 Data PRELIMINARY MS sin 2  = 0.2311 ± 0.00016 w MS Theory:

58. Q (GeV) sin 2  w Status in 1999

60. 0.240 0.238 0.236 0.234 0.232 0.230 1997 1998 1999 2000 Standard Model Cesium Atomic Parity Violation Result vs. Time sin 2  w (Colorado measurement) Modifications in the theoretical corrections to the atomic structure Wieman et al. Bennett Wieman Derevianko Dzuba Flambaum 20012002 Kozlov Porsev Tupitsyn Johnson Bednyhakov Soff Kuchiev Flambaum 2003

61. 77 Status Today sin 2  w

62. E158 Beyond Standard Model Implications... *Limit on  LL ~ 10 TeV *Limit on SO(10) Z’ ~ 900 GeV *Limit on lepton flavor violating coupling ~ 0.01G F (95% confidence level)

63. FUTURE: Low energy polarized electron scattering *Jefferson Lab *SLAC (could do it, but won’t)

64. The Qweak Experiment: A Search for New Physics at the TeV Scale Via a Measurement of the Proton’s Weak Charge December 3, 2001 D. Armstrong 1, T. Averett 1, J.D. Bowman 5, R. Carlini 9 (contact person), C.A. Davis 11 J. Erler 3, R. Ent 9, M. Finn 1, T.A. Forest 6, K. Johnston 6, R. Jones 2, S. Kowalski 8, L. Lee 7, A. Lung 9, D. Mack 9, S.A. Page 7, S. Penttila 5, M. Pitt 10, M. Poelker 9, W.D. Ramsay 7, M. Ramsey-Musolf 2,4, J. Rochel 9, N. Simicevic 6, G. Smith 9, R. Suleiman 8, S. Taylor 8, W.T.H. van Oers 7, S. Wells 6, S. Wilburn 5, S.A. Wood 9 1College of William and Mary, Williamsburg, VA 2University of Connecticut, Storrs, Connecticut 3David Rittenhouse Laboratory, University of Pennsylvania, Philadelphia, Pennsylvania (New address (1/1/2002): Instituto de Fisica, Universidad Nacional Autonoma de Mexico, 01000 Mexico D.F., Mexico) 4Kellogg Radiation Laboratory, California Institute of Technology, Pasadena, California 5Los Alamos National Laboratory, Los Alamos, New Mexico 6Louisiana Tech University, Ruston, Louisiana 7University of Manitoba, Winnipeg, Manitoba, Canada 8Massachusetts Institute of Technology, Cambridge, Massachusetts 9TJNAF, Newport News, VA 10Virginia Polytechnic Institute, Blacksburg, Virginia 11TRIUMF, Vancouver, Canada Approved January 2002

65. Jefferson Lab Qweak Experiment * 180  Amp current * 1 GeV beam * 2200 hours of data Elastic electron-proton scattering experiment

66. SLAC DIS-Parity Letter of Intent ~39 GeV polarized electrons scattering off deuterium target A LR ~ 10 -3 at Q 2 ~ 20 GeV 2 Measurement to 0.6% precision... Submitted: June 2003

67. Projected experimental uncertainty from DIS-parity proposal @ SLAC and Qweak experiment @ Jefferson Lab

68. LHC Not a parity experiment …  Has major impact on precision low energy tests for discovery potential Z’, supersymmetry, compositeness, leptoquarks, etc… in the TeV range

69. SUMMARY *Performed a first measurement of parity violation in e - e - scattering *Future parity experiments active *Complementary to collider experiments Final result publication in ~ 1/2 year