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Parity Violating Electron Scattering: Interplay Between Electroweak Physics and Hadronic Physics Weak Interaction Physic

Parity Violating Electron Scattering: Interplay Between Electroweak Physics and Hadronic Physics Weak Interaction Physics from the JLab Point of View. Krishna Kumar University of Massachusetts, Amherst Acknowledgement: J. Erler, C. Horowitz, W.J. Marciano, M.J. Ramsey-Musolf, K. Paschke,

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Parity Violating Electron Scattering: Interplay Between Electroweak Physics and Hadronic Physics Weak Interaction Physic

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  1. Parity Violating Electron Scattering:Interplay Between Electroweak Physics and Hadronic PhysicsWeak Interaction Physics from the JLab Point of View Krishna Kumar University of Massachusetts, Amherst Acknowledgement: J. Erler, C. Horowitz, W.J. Marciano, M.J. Ramsey-Musolf, K. Paschke, J. Piekerewicz, M. Pitt, P. Souder October 17, 2006 Physics of Nucleons and Nuclei: SURA Workshop, Washington D.C. Parity Violating Electron Scattering

  2. Weak Neutral Current (WNC) Interactions Parity is violated Parity is conserved Low energy WNC interactions (Q2<<MZ2) Z0 Historical Context: • 1960s: An Electroweak Model of Leptons (and quarks) • SU(2)L X U(1)Y gauge theory predicted the Z boson • sin2W introduced to predict lepton & quark Z couplings • 1973: antineutrino-electron scattering • First weak neutral current observation • Mid-70s: Does the Weak Neutral Current interfere with the Electromagnetic Current? • Central to establishing SU(2)L X U(1)Y • Gargamelle observes one e- event • First measurement of sin2W Consider fixed target electron scattering Parity Violating Electron Scattering

  3. Parity-Violating Electron Scattering E’ 4-momentum transfer  E Electron-proton Weak Scattering Ya. Zel’dovich (1959) Neutron  Decay Parity-violating APV ~ (GeV2) It was realized independently in the mid 70s at SLAC: APV in Deep Inelastic Scattering off liquid Deuterium: Q2 ~ 1 (GeV)2 Parity Violating Electron Scattering

  4. PV Electron Scattering off a Nucleus Elastic scattering: 0+0+ One form factor; charge monopole: cancels in the asymmetry ratio Spinless, isoscalar nucleus Feinberg (1975), Donnelly and Walecka (1975) APV independent of nuclear structure; nucleus acts as filter: different linear combination of quark couplings accessed For elastic scattering off nucleus: Q2 << 0.1 GeV2 APV ~ 1 ppm “Flux Integration”: Allows counting at high rates • Optical pumping of a GaAs wafer • Rapid helicity reversal • Control of helicity-correlated beam motion Spectrometer directs flux to background-free region MIT-Bates: P. Souder et al (1990) New innovative methods to control systematic effects Astat ~ 10-7, Asyst ~ 10-8 Parity Violating Electron Scattering

  5. Spinoff: Nucleon Structure Studies QCD and the Quark Model Sea quarks, especially strange quarks, can provide new insight Neutrino deep inelastic scattering Polarized target technology & high-luminosity polarized beams made new experiments feasible Parton distribution functions Fraction of nucleon momentum pN scattering: SU(3)f symmetry-breaking introduces uncertainties Strange mass: 0-20% • Semi-inclusive DIS (HERMES) • (Needs fragmentation functions) What about the nucleon’s charge and magnetization distributions? Part per billion systematic control facilitated new experimental program Parity Violating Electron Scattering

  6. Elastic Electroweak Scattering Backward angle Forward angle Z0 APV for elastic e-p scattering: Kaplan & Manohar (1988) McKeown (1989) GEs(Q2), GMs(Q2) Helium: Unique GE sensitivity Deuterium: Enhanced GA sensitivity Parity Violating Electron Scattering

  7. Overview of Experiments A4 Open geometry Fast counting calorimeter for background rejection GEs + 0.23 GMs at Q2 = 0.23 GeV2 GEs + 0.10 GMs at Q2 = 0.1 GeV2 GMs, GAe at Q2 = 0.1, 0.23, 0.5 GeV2 HAPPEX GEs + 0.39 GMs at Q2 = 0.48 GeV2 GEs + 0.08 GMs at Q2 = 0.1 GeV2 GEs at Q2 = 0.1 GeV2 (4He) G0 Open geometry Fast counting with magnetic spectrometer + TOF for background rejection GEs + hGMs over Q2 = [0.12,1.0] GeV2 GMs, GAe at Q2 = 0.23, 0.62 GeV2 SAMPLE open geometry, integrating GMs, (GA) at Q2 = 0.1 GeV2 Parity Violating Electron Scattering

  8. New HAPPEX Results (final) Hydrogen Hydrogen APV= -1.58  0.12(stat) 0.04(syst)ppm A(Gs=0) = -1.66 ppm 0.05 ppm Helium Asymmetry (ppm) APV = +6.40  0.23(stat) 0.12(syst)ppm A(Gs=0) = +6.37 ppm Araw correction ~11 ppb Slug nucl-ex/0609002, submitted to PRL Helium Asymmetry (ppm) normalization error ~ 2% Result insensitive to axial form factors Fit to world data consistent (R. Young et al, nucl-ex/0604010) Slug Parity Violating Electron Scattering

  9. Implications and Outlook Forward angle e-p data • Rapid variation at low Q2 unlikely • Await backward angle measurements from A4, G0 • Deuterium running will provide constraints on GA • One high precision point at Q2~0.6 GMs = 0.28 +/- 0.20 GEs = -0.006 +/- 0.016 ~0.2 +/- 0.5% of electric distribution ~3% +/- 2.3% of proton magnetic moment (<20% of isoscalar magnetic moment) • Approved program well-matched to ultimate sensitivity of the technique: charge symmetry, radiative corrections, axial form factors….. • Models dealing with “sea” properties are challenging • Experimentally, 20-year old quest nearing completion • Ultimate insight: unquenched Lattice QCD calculations with light chiral quarks HAPPEX-only fit suggests something even smaller: GMs = 0.18 +/- 0.27 GEs = -0.005 +/- 0.019 Technology pushed to new levels: opens new physics topics Parity Violating Electron Scattering

  10. Elastic Electroweak Scattering off 208Pb Donnelly, Dubach and Sick (1989) C. Horowitz, R. Michaels et al (2001) (APV) ~ 3% (Rp-Rn) ~ 1% Q2 ~ 0.01 GeV2 APV ~ 0.5 ppm  QpEM ~ 1 QnEM ~ 0 QnW ~ 1 A technically demanding measurement: QpW ~ 1 - 4sin2W • Rate ~ 2 GHz • Separate excited state ~ 2.5 MeV • Stat. Error ~ 15 ppb • Syst. Error ~ 1 to 2 % Comments on physics: Bill, Chuck & Jorge Comments on technology: Gordon • Tight control of beam properties • New “warm” septum • High power Lead target • New 18-bit ADC • New radiation-hard detector • Polarimetry upgrade All elements in place in 2008 Parity Violating Electron Scattering

  11. Beyond the Standard Model • New Particle Searches • Rare or Forbidden Processes • Symmetry Violations • Electroweak One-Loop Effects High Energy Colliders as well as Low Energy: Q2 << MZ2 Low Q2 offers complementary probes of physics at high energy scales • Neutrino Physics • Oscillations and the MSN matrix • Tritium Beta Decay and Double Beta Decay • Muon Physics • g-2 anomaly • Precision muon decay parameters • Charged lepton number violation • Semi-leptonic Weak Decays • Standard Model CP Violation • Tests of CKM unitarity • Anomalous charged current interactions • Search for Proton decay • Dark Matter Searches • Electric Dipole Moment Searches • Neutral Weak Interaction Studies Parity Violating Electron Scattering

  12. Comprehensive Search for New Neutral Current Interactions or Consider Eichten, Lane and Peskin, PRL50 (1983) Different ’s for all f1f2 combinations and L,R combinations Relying on specific models to sell a measurement is not good strategy: Models will go in and out of fashion over a 5-10 year span Neutral Current Interactions are Flavor Diagonal Any new physics model can be characterized in this way: Heavy Z’s, compositeness, extra dimensions… One goal of neutral current measurements at low energy AND colliders: Access  > 10 TeV for as many f1f2 and L,R combinations as possible Parity Violating Electron Scattering

  13. Colliders vs Low Q2 LEP & SLC accessed some parity-violating combinations but… LEPII, Tevatron access scales L’s ~ 10 TeV e.g. Tevatron dilepton spectra, quark pair production at LEPII - L,R combinations accessed are parity-conserving Window of opportunity for weak neutral current measurements at Q2<<MZ2 Parity Violating Electron Scattering

  14. Published & Future Measurements • Atomic Parity Violation • 133Cs6s to 7s transition • Future: Radioactive beams • Neutrino DIS: NuTeV • 3  deviation • Many hadronic physics issues • Parity-Violating electron-electron (Møller) scattering: SLAC E158 • Purely leptonic • Most precise measurement • Running of weak mixing angle Future • Elastic electron-proton scattering • Proton is “fundamental” at Q2<<0.1GeV2 (strange quark measurements) • Theory and experimental systematics under control • Deep-Inelastic scattering off deuterium • Jlab 11 GeV enables comprehensive measurements • Møller scattering • Jlab 11 GeV enables greatly improved figure-of-merit Parity Violating Electron Scattering

  15. Qweak at JLab Physics Asymmetry: Region 2: Horizontal drift chamber location Region 1: GEM Gas Electron Multiplier Mini-torus Quartz Cerenkov Bars (insensitive to non-relativistic particles) e- beam Lumi Monitors • (APV) ~ 3% • (sin2W) ~ ± 0.0007 • Design under way • Data ~ 2010 QTOR Magnet Region 3:Vertical Drift chambers Collimator System Trigger Scintillator APV in elastic e-p scattering Parity Violating Electron Scattering

  16. Lepton-Quark WNC Couplings (2009-10) NuTeV • NuTeV motivates closer look at lepton-quark WNC couplings • 4 model-independent e-q couplings to nail down • Implications for models of new TeV scale physics A V V A • C2i’s small & poorly known: difficult to measure in elastic scattering • PV Deep inelastic scattering experiment with high luminosity ~ 10 GeV beam • Possible after 12 GeV upgrade of Jefferson Lab Parity Violating Electron Scattering

  17. PV DIS at 11 GeV with an LD2 target For an isoscalar target like 2H, structure functions largely cancel in the ratio: (Q2 >> 1 GeV2 , W2 >> 4 GeV2, x ~ 0.3-0.5) • Must measure APV to 0.5% fractional accuracy! • Luminosity and beam quality available at JLab e- e- * Z* X N • Important constraint for Large Hadron Collider anomalies • However, extraction of C2i’s assumes nucleon with valence quarks • Need to characterize nucleon structure at high-x to high precision • This is one of the core missions of the 11 GeV Jlab program! Parity Violating Electron Scattering

  18. Precision High-x Physics with PV DIS 1% APV measurements Charge Symmetry Violation (CSV) at High x: clean observation possible? Blue curve: Gluck, Jimenez-Delgado, Reya +Thomas and Londergan For hydrogen 1H: Longstanding issue: d/u as x1 • Allows d/u measurement on a single proton! • Vector quark current! (electron is axial-vector) Parity Violating Electron Scattering

  19. A Vision for Precision PV DIS Physics • Hydrogen and Deuterium targets • Better than 2% errors • It is unlikely that any effects are larger than 10% • x-range 0.25-0.75 • W2 well over 4 GeV2 • Q2 range a factor of 2 for each x • (Except x~0.75) • Moderate running times • CW 90 µA at 11 GeV • 40 cm liquid H2 and D2 targets • Luminosity > 1038/cm2/s • solid angle > 200 msr • Count at 100 kHz • online pion rejection of 102 to 103 • Need BaBar, CDF or CLEOII Solenoid • roughly 10-15M$ project • Plan to make presentations at Symmetries and Hadrons Town Meetings Parity Violating Electron Scattering

  20. Weak Mixing Angle at HIGH Energy W. Marciano, CIPANP06, EW & BSM Session The Average: sin2θw = 0.23122(17) Rules out Technicolor! Favors SUSY! 3σ apart ALR AFB (Z→ bb) (also APV in Cs) (also Moller @ E158) sin2θw = 0.2322(3) ↓ mH = 480 +350-230 GeV S= +0.55 ± 17 sin2θw = 0.2310(3) ↓ mH = 35 +26-17 GeV S= -0.11 ± 17 Rules out SUSY! Favors Technicolor! Rules out the SM! JLab e2e @ 12 GeV • Tevatron & LHC will make some improvements on MW • sin2W improvements at hadron colliders very challenging • Must wait for “Giga-Z” option of ILC or Neutrino Factory • Jlab e2e coule be the best measurement until 2020 Parity Violating Electron Scattering

  21. Summary • New HAPPEX results on nucleon neutral weak form factors: • Helium: GsE = +0.002  0.014(stat)  0.007(syst) (Q2 = 0.077 GeV2) • Hydrogen: GsE+0.09GsM = +0.0070.011(stat)0.005(syst)0.004(FF) • Final measurements to be completed within two years • A clean measurement of the neutron distribution in 208Pb: implications for nuclear structure & neutron star properties • Precision sin2W at low energy constrain TeV scale physics • Running of weak mixing angle established at 6 • Qweak will provide complementary information • Møller scattering @ JLab 12 GeV competes with colliders • New era of PV DIS measurements with JLab 12 GeV upgrade • We prepare to make a pitch during Long Range Planning Parity Violating Electron Scattering

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