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Kent Paschke

Strangeness Content of the Nucleon. Kent Paschke. International Workshop on Neutrino Factories, Super Beams and Beta Beams July 25, 2012. Magnetic moment, charge radius. Spin 0 - -10%. ,. “Static” Strange Quarks in the Nucleon. Mass 0-30%. Momentum ~ 4%.

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Kent Paschke

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  1. Strangeness Content of the Nucleon Kent Paschke International Workshop on Neutrino Factories, Super Beams and Beta Beams July 25, 2012

  2. Magnetic moment, charge radius Spin 0 - -10% , “Static” Strange Quarks in the Nucleon Mass 0-30% Momentum ~ 4% Strange quarks exist in the nucleon at short distance scales. Strange contributions to nucleon matrix elements are unsettled Kent Paschke NuFACT, Williamsburg, Virginia, July 25, 2012

  3. Recent lattice results claim high precision with small values for strange quark mass contribution 15-60 MeV = 36 ± 7 MeV Strangeness Nucleon Sigma Term R.D. Young and A.W. Thomas, Nuclear Physics A 844 (2010) 266c The spin-independent neutralino-nucleon scattering cross section as a function of ΣπN. Dark Matter Searches Strange quarks coupling to the Higgs is much higher than that of the u/d flavors. The spin independent neutralino-nucleon coupling varies by an order of magnitude depending on the strange condensate of the nucleon Ellis et al, Phys.Rev. D77 (2008) 065026, arXiv:0801.3656 σ0 estimated from known SU(3) breaking in the baryon octet: 36 ± 7 MeV Analyses of experimental data (πN scattering) implied large values of ΣπN ~ 65 MeV -> Large but uncertain σs ~ 350 MeV Kent Paschke NuFACT, Williamsburg, Virginia, July 25, 2012

  4. Strange Spin Do the strange quarks in the sea play a significant role in the electric/magnetic charge distributions in the nucleon? Other Open Questions in Nucleonic Strangeness ? Originally motivated by the “spin problem”, but remains an important question in nucleon structure The spin dependent neutralino-nucleon coupling depends on Δs NuTeV Anomaly NuTeV published a 3σ deviation from the standard model A leading hypothesis is that a signficant fraction is explained by an asymmetry in the strange sea: Kent Paschke NuFACT, Williamsburg, Virginia, July 25, 2012

  5. Charge Symmetry Measure neutral weak proton vector form-factor Three equations and three unknowns Extracting the Strange Vector Form Factor Measuring all three enables separation of up, down and strange contributions Two equations and three unknowns The weak form factor is accessible via parity violation Kent Paschke NuFACT, Williamsburg, Virginia, July 25, 2012

  6. Spin=0,T=0 (4He): Proton: Deuterium: Z0 γ γ Backward angle p Strange Form Factors in PVeS Forward angle ~ few parts per million GsE only! Enhanced GA nuclear corrections: forward angle, low Q2 only Back-angle quasi-elastic. 2 “Anapole” radiative corrections are problematic Asymmetry of longitudinal polarized electron beam from unpolarized target Kent Paschke NuFACT, Williamsburg, Virginia, July 25, 2012

  7. The Axial Term and the Anapole Moment Anapole Moment Correction: Multiquark weak interaction in RA(T=1), RA(T=0) Zhu, Puglia, Holstein, Ramsey-Musolf, Phys. Rev. D 62, 033008 • Model dependent calculation, with large uncertainty (~30% on axial FF) • Dominates Uncertainty in Axial Term Difficult to achieve tight experimental constraint Reduced in importance for forward-angle measurements Axial form-factors GAp, GAn • Determined at Q2=0 from neutron and hyperon decay parameters (isospin and SU(3) symmetries) • Q2 dependence often assumed to be dipole form, fit to ν DIS and π electroproduction • Includes also Δs, fit from ν-DIS data (with significant uncertainties) Kent Paschke NuFACT, Williamsburg, Virginia, July 25, 2012

  8. = −0.085 ± 0.013(th) ± 0.008(exp) ± 0.009(evol) Axial Strange Form-Factor ~ -0.01 ± 0.012 (exp) Strange axial form-factor related to integral over spin-dependent strange PDFs via QCD sum rule Extrapolation of measurements of spin dependent structure functions are ambiguous: HERMES (inclusive) Phys. Rev. D75 012007 (2007) = 0.028 ± 0.033(stat) ± 0.009(ev) HERMES (semi-inclusive) COMPASS (semi-inclusive) DSSV helicity PDF fit reflects the HERMES SIDIS dominance: positive above x~0.05, with inclusive data dominating at lower x de Florian, Sassot, Stratmann and Vogelsang, Phys. Rev. D80 034030 (2009) Kent Paschke NuFACT, Williamsburg, Virginia, July 25, 2012

  9. Limited precision and moderately high Q2 reduce precision of bound on Would have provided a precise, low Q2 measurement using a ratio of NC and CC quasi-elastic cross-sections, projected = −0.21 ± 0.10 (exp) ± 0.10 (FF) Neutrino NC elastic measurements for GAs Fitting cross-section data from NC scattering in E734 Very sensitive to Q2 dependence (axial mass MA) L. A. Ahrens et al., Phys. Rev. D35, 785 (1987). G. Garvey et al., Phys. Rev. C48, 761 (1993). Finesse In any case, this is a small contributor to the axial uncertainty due to radiative corrections for the vector strange FF measurements Kent Paschke NuFACT, Williamsburg, Virginia, July 25, 2012

  10. Elastic Hall A Parity: Integrating in the High Resolution Spectrometers detector Inelastic Quad target Dipole parts per million Q Q Techniques for high flux, to get few percent precision on 1-20 parts per million asymmetry Very clean separation of elastic events by HRS optics no PID needed; detector sees only elastic events Psuedo-random, rapid helicity flip • Lead - Lucite Cerenkov Shower Calorimeter • phototube current integrated over fixed time periods Kent Paschke NuFACT, Williamsburg, Virginia, July 25, 2012

  11. Experimental Overview A4 SAMPLE Open geometry Fast counting calorimeter for background rejection Forward and Backward angles open geometry, integrating, back-angle only HAPPEX Precision spectrometer, integrating Forward angle, also 4He at low Q2 G0 Open geometry Fast counting with magnetic spectrometer + TOF for background rejection Forward and Backward angles over a range of Q2 Kent Paschke NuFACT, Williamsburg, Virginia, July 25, 2012

  12. Forward-angle proton scattering “No net vector strangeness” line Significant background challenges in G0 measurement Combining results from forward-angle proton scattering (similar beam energies): • ANS error: precision of EMFF (including 2γ), Anapole correction, and γZ box diagrams • Using experimental determination for axial form factor would increase total Ans uncertainty about 50% • Additional data at backward angles, and 2H and 4He target Kent Paschke NuFACT, Williamsburg, Virginia, July 25, 2012

  13. World Data at Q2~0.1 GeV2 ~3% +/- 2% of proton magnetic moment ~0.2 +/- 0.5% of Electric FF 95% Caution: the combined fit is approximate. Correlated errors and assumptions not taken into account. For somewhat more careful treatment, see published fits by: R. Gonzalez-Jimenez, J.A. Caballero, T.W. Donnelly, arXiv:1111.6918 or R. Young et al., Phys. Rev. Lett 97, 102002 (2006) or J.Liu et al., Phys. Rev. C 76, 025202 (2007) Kent Paschke NuFACT, Williamsburg, Virginia, July 25, 2012

  14. World data on Gs Q2 ~ 0.22 Q2 ~ 0.62 At Q2 ~ 0.1 GeV2, Gs < few percent of Gp all forward-angle proton data Kent Paschke NuFACT, Williamsburg, Virginia, July 25, 2012

  15. Simple fit: GEs = ρs*τ GMs = μs Simple fit Fit includes only data Q2 < 0.65 GeV2 G0 Global error allowed to float with unit constraint Leading Order Fit • Simple fit (including all data, even if not shown) • Parameterization doesn’t matter... just “no bumps” • Data consistency is good (~20% confidence level) • Slight positive preference but low statistical significance • Contributions smaller than few percent of proton electric/magnetic form factors Kent Paschke NuFACT, Williamsburg, Virginia, July 25, 2012

  16. Parameterizations GEs = ρs*τ GMs = μs Fit includes all world data Q2 < 0.65 GeV2 G0 Global error allowed to float with unit constraint Models would need “bumps” to find significant strange effects GEs = ρs*galster GMs = μs*dipole GEs = ρs* τ + a2*τ2 GMs = μs + m2*τ Kent Paschke NuFACT, Williamsburg, Virginia, July 25, 2012

  17. Considering only the 4 HAPPEX measurements • High precision • Small systematic error • ε>0.95 - relatively clean theoretical interpretation Kent Paschke NuFACT, Williamsburg, Virginia, July 25, 2012

  18. QCD models Model guidance is unclear: kaon loops, vector dominance, Skyrme model, chiral quark model, dispersion relations, NJL model, quark-meson coupling model, chiral bag model, HBChPT, chiral hyperbag, QCD equalities, … Recent significant progress in Lattice QCD: - Dong, Liu, Williams PRD 58(1998)074504 - Lewis, Wilcox, Woloshyn PRD 67(2003)013003 - Leinweber, et al.,PRL 94(2005) 212001; 97 (2006) 022001 - Lin, arXiv:0707:3844 - Wang et al, Phys.Rev. C79 (2009) 065202 - Doi et al., Phys.Rev. D80 (2009) 094503 these all suggest very small effects with precision an order of magnitude beyond empirical constraints - predictions are experimentally indistinguishable from zero Kent Paschke NuFACT, Williamsburg, Virginia, July 25, 2012

  19. The Axial Term and the Anapole Moment Young et al., Phys.Rev.Lett. 97 (2006) 102002, nucl-ex/0604010 G0 results Anapole Moment Correction: Multiquark weak interaction in RA(T=1), RA(T=0) G0 Collaboration, Phys.Rev.Lett. 104 (2010) 012001 (preliminary) Difficult to improve on theoretical bound Uncertain Q2 dependence Worse, if you assume that the correction might independently affect GAp and GAn Leinweber Zhu Zhu Kent Paschke NuFACT, Williamsburg, Virginia, July 25, 2012

  20. Proton Weak Charge slope due to proton structure Proton weak charge precisely known from EW gauge theory and precision EW at the Z-pole If measurement at low energy comes up different, indicates proton charged for some other (parity-violating) interaction Global fit of existing strange-quark program data provides constraint on Standard Model Kent Paschke NuFACT, Williamsburg, Virginia, July 25, 2012

  21. Bounding the vector weak charge SM value With this parameterization for hadronic effects, what can be said about the Standard Model parameters? Neutral weak charge of Up, Down quarks QpW = 2 C1u + C1d These “form factor” measurements offer a powerful constraint on new physics R. Young et al., PRL 99 122003 (2007) Kent Paschke NuFACT, Williamsburg, Virginia, July 25, 2012

  22. Proton Weak Charge with QWeak Dedicated proton form-factor at very low Q2: proton weak charge to 4% Run concluded this May. Analysis underway. First results at October DNP! Figure: R.Young δQWp=4% • Non-perturbative theoryg ~ 2πΛ~ 29 TeV • Extra Z’g ~ 0.45 m Z’~ 2.1 TeV Kent Paschke NuFACT, Williamsburg, Virginia, July 25, 2012

  23. Pioneering Strange Quark Studies 3rd Generation Future Precision Electroweak Physics with e- beam SOLID: significant interplay with ν studies • Future: • Qweak-electron (MOLLER at JLab) • Quark axial charges + nuclear studies (SOLID at JLab) • super Qweak-proton (P2 at Mainz) • Steady progress in technology: • part per billion systematic control • 1% systematic control • Major developments in • photocathodes ( I&P ) • polarimetry • high power cryotargets • nanometer beam stability • precision beam diagnostics • low noise electronics • radiation hard detectors • pioneering • recent • next generation • future Kent Paschke LNS Colloquium, September 2011

  24. Vector Strange Form Factors are Small Q2 ~ 0.62 Q2 ~ 0.1 Q2 ~ 0.22 • Global results are consistent with strangeness contributions less than a few percent of the electromagnetic structure of the nucleon • Recent lattice results indicate values smaller than these uncertainties • Further improvements in precision on strange form factors would require additional theoretical (radiative corrections) and empirical (vector FF) input for interpretation Vector strange quark program is winding down... ...nuclear and fundamental interaction studies with parity-violating electron scattering continue Kent Paschke NuFACT, Williamsburg, Virginia, July 25, 2012

  25. Kent Paschke NuFACT, Williamsburg, Virginia, July 25, 2012

  26. Kent Paschke NuFACT, Williamsburg, Virginia, July 25, 2012

  27. Backup Kent Paschke NuFACT, Williamsburg, Virginia, July 25, 2012

  28. Sibirtsev, Blunden, Melnitchouk, Thomas (2010) Q2 dependent, but incomplete resonant states Complete calculations, but only at Q2 =0 γZ box contributions Also results from: Rislow, Carlson (2010), Gorchtein, Horowitz, M. Ramsey-Musolf(2011) 1%-few% for APV ~10-3 for APV Tjon, Blunden, Melnitchouk (2009) Also results from Zhou, Kao, Yang, Nagata (2010) Recent interest in radiative corrections which remain significant at low Q2 Current status: few% uncertainty over measurement range, from 20-50% of Ans error. Precision will be improved. Kent Paschke NuFACT, Williamsburg, Virginia, July 25, 2012

  29. SAMPLE • Bates Laboratory, 1998-2001 • Backward angle, H and 2H Q.E. at low Q2 • Mirrors focus Cerenkov light from backscattered particles into shielded PMTs • Analog integration of PMT during beam burst • No magnetic or T.o.F. spectrometer; background is not excluded • Background Dilution: • Non-light background 15-30% • Non-Cerenkov background 10-15% • Pion decay background 5-10% Measured in specialized runs GEANT simulation Kent Paschke NuFACT, Williamsburg, Virginia, July 25, 2012

  30. PVA4 at Mainz MAMI Microtron, 2000-present Forward and backward angles, Hydrogen, D2 Q2 = 0.6, 0.23, 0.1 GeV2 1022 PbF2calorimeter crystals distinguish elastic via energy resolution Specialized fast counting electronics self-trigger and histogram energy distributions in overlapping 3x3 modules Elastic rate: 10 MHz, total rate 100 MHz Calorimeter: 1022 PbF2 crystals 10 cm LH2 target LuMo 20 μA, 80% polarized beam Scintillator paddles in coincidence to tag charge in backangle studies Kent Paschke NuFACT, Williamsburg, Virginia, July 25, 2012

  31. pions,background elastic protons G0 elastic protons inelastic protons detectors lead collimators beam target • JLab, 2004 Forward angle H • Duty factor of 499 MHz CEBAF beam reduced to 31 MHz • Recoil protons detected in scintillators, segmentation defines Q2 point • T.o.F through toroidal spectrometer,Time histogram from specialized electronics • Simultaneous Q2 = [0.16,1] GeV2 Kent Paschke NuFACT, Williamsburg, Virginia, July 25, 2012

  32. JLab, 2006 Back angle H, D2 One Q2 point for each beam energy “tracking+PID” from magnetic spectrometer G0 Backward Angle Electron detection Turn magnet/detector package around Add Cryostat Exit Detectors (“CEDs”) to define electron trajectory Add aerogel Cerenkovs to reject pions Kent Paschke NuFACT, Williamsburg, Virginia, July 25, 2012

  33. Subtracting off the CC axial term Combining with PVeS Simultaneous fit E734 with PVeS to control vector strange form factor contributions S. Pate et al., Phys.Rev. C78 (2008) 015207 How well is Q2 dependence known? (recent Miniboone and K2K results raise questions) Robust over models of Q2 dependence? Anapole corrections to PVeS? Kent Paschke NuFACT, Williamsburg, Virginia, July 25, 2012

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