1. 1 SLUO 2004SLAC E-158 A Study of Parity Violation in Møller Scattering Mike Woods, SLAC SLUO Meeting, July 2004 E158 Goal:  sin 2  W = +/- 0.001 Best measurement of  W away from the Z-pole

2. 2 SLUO 2004SLAC E-158 For E158, E=48 GeV, Q 2 =0.03 GeV 2 At tree level, A PV = -3 x 10 -7 For a polarized electron beam and an unpolarized electron target, Parity Violation in Moller Scattering

3. 3 SLUO 2004SLAC E-158 Parity Violation, Weak Mixing Angle Weak Mixing Angle LH couplingRH coupling SU(2) L x U(1), with isotriplet field A i  SU(2) L coupling constant is g and isosinglet field B  U(1) coupling constant is g’ A 1 , A 2  are charged fields and correspond to W +, W - particles A 3 , B  are neutral and can mix, giving the Z 0 and  particles Weak mixing angle: g’=g tan  W Electroweak Theory:

4. 4 SLUO 2004SLAC E-158 Parity Violation at Low Q 2  -Z interference) first observation of PV in weak neutral scattering cornerstone experiment that solidified the Standard Model developed by Glashow, Weinberg and Salam Studies pioneered by SLAC E-122 (lepton-nucleon DIS): (A PV ~ 10 -4 )

5. 5 SLUO 2004SLAC E-158 Parity Violation at the Z-pole Very precise measurements by SLD at SLAC best measurement of weak mixing angle best indirect constraint on the Higgs mass (A PV ~ -0.15)

6. 6 SLUO 2004SLAC E-158 Electroweak Measurements away from the Z-pole E-158 probes TeV-scale physics: contact interactions,  LL ~ 10 TeV Z’ ~ 1 TeV

7. 7 SLUO 2004SLAC E-158 Low Q 2 Measurements of  W Purely leptonic reaction g ee ~ 1 - 4sin 2  W

8. 8 SLUO 2004SLAC E-158 2 GHz 45 GeV P=85% 5x10 11 e - /pulse L ~ 10 38 cm -2 s -1 integrating flux counter LH2 4-7 mrad End Station A

9. 9 SLUO 2004SLAC E-158 UC Berkeley Caltech Jefferson Lab Princeton Saclay SLAC Smith College Syracuse UMass Virginia 7 Ph.D. Students 60 physicists Sep 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

10. 10 SLUO 2004SLAC E-158 Key Ingredients High beam polarization and current Largest high-power LH2 target in the world Spectrometer optimized for Møller kinematics Stringent control of helicity-dependent systematics. Passive asymmetry reversals

11. 11 SLUO 2004SLAC E-158 ParameterE-158NLC-500 Charge/Train 5 x 10 11 14.4 x 10 11 Repetition Rate 120 Hz Energy 45 GeV250 GeV e - Polarization 85-90%80% Train Length 270ns267ns Microbunch spacing 0.3ns1.4ns Beam Loading 13%22% Energy Spread 0.15%0.3% E-158 Beam (and comparison with 500 GeV Linear Collider Design) E-158 profited considerably from the photocathode R&D carried out for NLC (gradient-doped strained superlattice cathode in Run 3 had P~90%!)

12. 12 SLUO 2004SLAC E-158 Can compare measurements of neighboring devices to determine the precision of the measurement. Energy dithering region  BPM ~2 microns  energy ~1 MeV Agreement (MeV) BPM24 X (MeV) BPM12 X (MeV)  toroid ~30 ppm Beam Monitoring Devices

13. 13 SLUO 2004SLAC E-158 End Station A

14. 14 SLUO 2004SLAC E-158 Scattering Chamber and Spectrometer Magnets LH 2 Scattering Chamber ‘Sewer Pipe’ in front of Detector Cart

15. 15 SLUO 2004SLAC E-158 MOLLER, ep are (copper/fused silica fiber) calorimeters PION is a quartz bar Cherenkov LUMI is an ion chamber with Al pre-radiator All detectors have azymuthal segmentation, and have PMT readout to 16-bit ADCDetectors

16. 16 SLUO 2004SLAC E-158 ep Background to Moller sample: 6% from elastic scattering 1% from inelastic scattering (30±6) ppb correction QC1B (main acceptance) collimator Insertable QC1A collimator - used for polarimetry Scattered Flux Profile ee Moller signal ep Moller Detectorep Detector

17. 17 SLUO 2004SLAC E-158 Experimental Features Beam helicity is chosen pseudo-randomly at 120 Hz use electo-optical Pockels cell in Polarized Light Source sequence of pulse quadruplets; one quadruplet every 33 ms: Also, False Asymmetry Reversals: (reverse false beam position and angle asymmetries; physics asymmetry unchanged) Insertable “-I/+I” Inverter in Polarized Light Source ‘Null Asymmetry’ Cross-check is provided by a Luminosity Monitor measure very forward angle e-p (Mott) and Moller scattering Physics Asymmetry Reversals: Insertable Halfwave Plate in Polarized Light Source (g-2) spin precession in A-line (45 GeV and 48 GeV data)

18. 18 SLUO 2004SLAC E-158 A PV Measurement 1. Measure asymmetry for each pair of pulses, p, coefficients determined experimentally by regression or from dithering coefficients 2. Correct for difference in R/L beam properties, charge, position, angle, energy R-L differences 3. Sum over all pulse pairs, 4. Obtain physics asymmetry: backgrounds beam polarization, linearity background dilutions

19. 19 SLUO 2004SLAC E-158 Observe ~ 2.5 ppm asymmetry First measurement of single-spin transverse asymmetry in e-e scattering. Flips sign at 43 GeV Asymmetry vs  Two-photon exchange; QED measurement with E-158 Theory References: 1. A. O. Barut and C. Fronsdal, (1960) 2. L. L. DeRaad, Jr. and Y. J. Ng (1975) 3. Lance Dixon and Marc Schreiber; hep-ph/0402221 Transverse ee Asymmetry (Raw) Transverse ee Asymmetry i) Interesting signal, ii) potential background for A PV measurement iii) Studying its utility for calibration of polarization scale

20. 20 SLUO 2004SLAC E-158 Has opposite sign elastic ep asymmetry should be negligible ~O(10 -10 ) ~ 25% inelastic ep Few percent pions (asymmetry small) Proton structure and QCD at E158 ! ~ 24 hrs of data Transverse ep Asymmetry (Raw) Transverse ep Asymmetry Asymmetry vs 

21. 21 SLUO 2004SLAC E-158 ep Detector Data (Run 1) Ratio of asymmetries: A PV (48 GeV) /A PV (45 GeV) = 1.25 ± 0.08 (stat) ± 0.03 (syst) A RAW (45 GeV) = -1.36 ± 0.05 ppm (stat. only) A RAW (48 GeV) = -1.70 ± 0.08 ppm (stat. only)  Consistent with expectations for inelastic ep asymmetry

22. 22 SLUO 2004SLAC E-158 Source  A (ppb) f Beam asymmetries(-) ± 4- Beam spotsize0 ± 1- Transverse polarization-4 ± 2- ep elastic-8 ± 20.058 ± 0.007 ep inelastic-22 ± 60.009 ± 0.003 Brem and Compton electrons0 ± 10.005 ± 0.002 Pions1 ± 10.001 ± 0.001 High energy photons3 ± 30.004 ± 0.002 Synchrotron photons0 ± 20.0015 ± 0.0005 Neutrons-1 ± 10.0006 ± 0.0002 TOTAL-31 ± 80.079 ± 0.009 A PV Corrections,  A, and dilution factors, f *Beam polarization measured using polarized foil target; same spectrometer used with dedicated movable detector

23. 23 SLUO 2004SLAC E-158 Run I Results Published

24. 24 SLUO 2004SLAC E-158 A PV (e - e - at Q 2 = 0.026 GeV 2 ): -128  14 (stat)  12 (syst) parts per billion (preliminary) Significance of parity nonconservation in Møller scattering: 8  Moller Asymmetry, APV

25. 25 SLUO 2004SLAC E-158 from A PV to sin 2  W eff where: is an analyzing power factor; depends on kinematics and experimental geometry. Uncertainty is 1.7%. (y = Q 2 /s) F brem = (1.016 ± 0.005) is a correction for ISR and FSR; (but thick target ISR and FSR effects are included in the analyzing power calculation from a detailed MonteCarlo study)  W eff is derived from an effective coupling constant, g ee eff, for the Zee coupling, with loop and vertex electroweak corrections absorbed into g ee eff

26. 26 SLUO 2004SLAC E-158 E158 Weak Mixing Angle Result Q 2 -dependence of  W 77

27. 27 SLUO 2004SLAC E-158 Summary: Physics results from E-158 Electro-weak parity violation first observation of parity violation in Møller scattering (8  ) running of the weak mixing angle established (7  ) Probing TeV-scale physics: ~10 TeV limit on  LL, ~900 GeV limit on SO(10) Z’ inelastic e-p asymmetry consistent with quark picture Transverse asymmetries First measurement of e-e transverse asymmetry (QED) e-p transverse asymmetry measured (QCD) Weak Mixing Angle Preliminary Results using all data A PV (Moller) = (-128 ± 14 ±12) ppb sin 2  W MS (M Z 2 ) = 0.2330 ± 0.0011 (stat) ±0.0010 (syst) Best measurement of the weak mixing angle away from the Z-pole!