Parity Violation in Electron Scattering Emlyn Hughes SLAC DOE Review June 2, 2004 *SLAC E122 *SLAC E158 *FUTURE

Polarized Electron Scattering e-   unpolarized quarks or electrons or protons Parity conserving Parity violating

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

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

End Station A

SLAC E122

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

Reversed every few runs 120 Hz

SLAC E122 waveplate reversal

Parity-violating asymmetry SLAC E122 waveplate reversal

SLAC E122 Energy Scan Parity-violating asymmetry

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

Atomic Parity Violation Bismuth

Atomic Parity Violation Bismuth

Atomic Parity Violation Bismuth

Atomic Parity Violation Bismuth E122

LEP and SLC e + e - collider  sin 2  w = (PDG2002)from Z pole measurements TODAY...

Q (GeV) sin 2  w Status in 1999 ~5%

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

UC Berkeley Caltech Jefferson Lab Princeton Saclay SLAC Smith College Syracuse UMass Virginia 7 Ph.D. Students 60 physicists Sept 97: EPAC approval : 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

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

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

STATISTICS # electrons per pulse10 7 Rep rate (120 Hz)10 9 Seconds/day days10 16  A ~ 10 -8

II. BEAM MONITORING

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

III. Beam Asymmetries Polarized source

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

A PV vs. time ppb

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

ep Detector Asymmetry

Transversely Polarized Beam

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

Run I & II

Run I

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

A PV =  160  21 (stat)  17 (syst) ppb sin 2  = ± (stat) ± (syst) At Q 2 = (GeV/c) 2 …. w RUN I & II PRELIMINARY MS sin 2  = ± w MS Theory:

Q (GeV) sin 2  w Status in 1999

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 Kozlov Porsev Tupitsyn Johnson Bednyhakov Soff Kuchiev Flambaum 2003

Q (GeV) sin 2  w Status today Run I & II

sin 2  w Q (GeV) Including E158 projections... Run I & II E158 Projected Error bar

Beyond Standard Model Implications... *Limit on  LL ~ 7 TeV *Limit on Z  ~ 400 GeV *Limit on lepton flavor violating coupling ~ 0.02G F  Limits will improve with new data

Future Measurements

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

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

Correctionf bkg  f bkg ) A corr (ppb)  A corr ) (ppb) Beam first order---3 Beam higher orders---10 Beam spotsize--01 Transverse asymmetry---83 High energy photons Synchrotron photons Neutrons ep elastic ep inelastic Pions TOTAL Run I Systematics

Normalization Factor f  (f) Dilutions Polarization Analyzing power Linearity Run I Dilutions

Correctionf bkg  f bkg ) A corr (ppb)  A corr ) (ppb) Beam first order---3 Beam higher orders---15 Beam spotsize--01 Transverse asymmetry---53 High energy photons Synchrotron photons Neutrons ep elastic ep inelastic Pions TOTAL Run II Systematics

Normalization Factor f  (f) Dilutions Polarization Analyzing power Linearity Run II Dilutions

A PV (Run I) = -176  30 (stat)  20 (syst) ppb (5  significance) A PV (Run II) = -145  28 (stat)  23 (syst) ppb (4  significance) A PV (Run I+II) = -161  21 (stat)  17 (syst) ppb (6  significance) Asymmetry Results

 Standard Model prediction: ± (Czarnecki, Marciano, 2000) sin 2  eff (Run I) = ± (stat) ± (syst) (-1.0  from Standard Model) sin 2  eff (Run II) = ± (stat) ± (syst) (-0.1  from Standard Model) sin 2  eff (Run I) = ± (stat) ± (syst) (-0.8  from Standard Model) Electroweak Mixing Parameter