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Strange Quarks in the Nucleon Sea Results from Happex II

Strange Quarks in the Nucleon Sea Results from Happex II. Konrad A. Aniol, CSULA. Recent Talks by the HAPPEX Collaboration. See these talks for greater detail. http://hallaweb.jlab.org/experiment/HAPPEX/pubsandtalks.html.

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Strange Quarks in the Nucleon Sea Results from Happex II

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  1. StrangeQuarks in the Nucleon Sea Results from Happex II Konrad A. Aniol, CSULA

  2. Recent Talks by the HAPPEX Collaboration See these talks for greater detail http://hallaweb.jlab.org/experiment/HAPPEX/pubsandtalks.html APS Meeting: Parity-Violation Electron Scattering on Hydrogen and Helium and Strangeness in the Nucleon, 23 April 2006 - Paul Souder (PPT) TJNAF Seminar: Results from the 2005 HAPPEX-II Run, 21 April 2006 - Kent Paschke (PPT) Kent Paschke, University of Massachusetts Thesis Students Lisa Kaufman, University of Massachusetts Bryan Moffit, College of William and Mary Hachemi Benaoum, Syracuse University Ryan Snyder, University of Virginia

  3. Structure of the Nucleon is of Fundamental Interest 99.9% of baryonic matter is contained in the nucleon A hierarchy of structures Molecules = Satoms, massmolecule =Smassatoms Atom = S(nuclei + electrons), matom=mnuclei+melectrons Nucleus = Snucleons, mnucleus Zmp+Nmn Nucleon=S(quarks+gluons), mnucleon mquarks !

  4. From PDG, mu is 1.5 to 4 MeV md is 4 to 8 MeV Proton flavor content is uud, mp 2mu + md Example of origin of proton’s mass, PRL 74 (1071) 1995, X. Ji Quark kinetic + potential energy = 1/3 mnucleon Total gluon energy = 7/12 mnucleon Quark masses = 1/12 mnucleon Conclude – nucleon mass has significant gluon field contribution expect significant amounts of pairs to be present. nucleon sea quarks are important components of the nucleon

  5. How can we determine the quark content of the nucleon? Constituent quarks are quasi-particles and become heavy fermions through the strong interactions. g qc uc qc g uc A constituent u quark has spin ½ and is a dynamical system.

  6. Are strange sea quarks present in the nucleon? Charged-current neutrino and anti-neutrino scattering reveal the presence of strange and anti-strange quarks. The charm quarks decay semileptonically to positive muons. Muon neutrinos thus produce positive and negative muon pairs. Likewise for muon anti-neutrinos:

  7. Strange Quarks in the Nucleon Strange Sea measured in nN scattering Strange sea is well-known, but contributions to nucleon matrix elements are somewhat unsettled Static nucleon properties ? • Spin polarized DIS • Inclusive: Ds = -0.10 ± 0.06 • uncertainties from SU(3), extrapolation • Semi-inclusive: Ds = 0.03± 0.03 • BUT new HERMES data determine that Ds = 0 ! • Strange mass • pN scattering: 0-30%of nucleon mass Strange vector FF electromagnetic structure ?

  8. Parts of the Lagrangian responsible for neutral current scattering photon Z boson Electroweak coupling of charged fundamental particles Note that the fermion fields yi are the same for photon or Z boson coupling. Only the coupling constants change.

  9. Electroweak coupling constants s -1/2 + 2sin2qW -1/2 -1/2 -1 e

  10. Neutral Currents andWeak-Electromagnetic Interference Electron Scattering off Nucleons & Nuclei

  11. Asymmetry terms for eP or eN scattering. HAPPEX is not sensitive to the AA term for forward angle scattering

  12. Flavor Separation of Nucleon Form Factors (assumes heavy quarks are negligible) Measuring cannot separate all three flavors Adding in a measurement of and assuming charge symmetry then we can write

  13. For 4He the asymmetry does not contain magnetic terms

  14. A B C Hall A Jefferson Laboratory CEBAF Continuous Electron Beam Accelerator Facility • Features: • Polarized Source • Quiet Accelerator • Precision • Spectrometers • in Hall A Polarized e- Source

  15. HAPPEX Experiment 1998-99: Q2=0.5 GeV2, 1H 2004-06: Q2=0.1 GeV2, 1H, 4He 2008:Q2=0.6, 1H The HAPPEX Collaboration California State University, Los Angeles - Syracuse University - DSM/DAPNIA/SPhN CEA Saclay - Thomas Jefferson National Accelerator Facility- INFN, Rome - INFN, Bari - Massachusetts Institute of Technology - Harvard University – Temple University – Smith College - University of Virginia - University of Massachusetts – College of William and Mary

  16. Hall A at Jefferson Lab Polarimeters Compton 1.5-2% syst Continuous Møller 2-3% syst Target 400 W transverse flow 20 cm, LH2 20 cm, 200 psi 4He High Resolution Spectrometer S+QQDQ 5 mstr over 4o-8o

  17. PMT Elastic Rate: 1H: 120 MHz Cherenkov cones 4He: 12 MHz PMT Overlap the elastic line above the focal plane and integrate the flux Very clean separation of elastic events by HRS optics  High Resolution Spectrometers 100 x 600 mm 12 m dispersion sweeps away inelastic events • Brass-Quartz Integrating Cerenkov Shower Calorimeter • Insensitive to background • Directional sensitivity • High-resolution • Rad hard Large dispersion and heavy shielding reduce backgrounds at the focal plane

  18. High-Power Cryogenic Target New "race track" design – 20 cm (transverse cryogen flow) CSULA design and fabrication. 20 cm 1.8% R.L. LH2 20 cm 2.2% R.L. 4He gas cell • Cold (6.6K), dense (230 psi) Al wall thickness • 4 mils (H) • 10 mils (He)

  19. Polarized Source High Pe High Q.E. Low Apower • Optical pumping of solid-state photocathode • High Polarization • Pockels cell allows rapid helicity flip • Careful configuration to reduce beam asymmetries. • Slow helicity reversal further to cancel beam asymmetries controls effective analyzing power Tune residual linear pol. Slow helicity reversal Intensity Attenuator (charge Feedback)

  20. Asymmetry (ppm) Slug 4He Preliminary Results Raw Parity Violating Asymmetry 35 M pairs, total width ~1130 ppm Araw correction ~ 0.12 ppm Helicity Window Pair Asymmetry Q2 = 0.07725 ± 0.0007 GeV2 Araw = 5.253 ppm 0.191 ppm (stat)

  21. Asymmetry (ppm) Slug 1H Preliminary Results Raw Parity Violating Asymmetry ~25 M pairs, width ~540 ppm Araw correction ~11 ppb Helicity Window Pair Asymmetry Q2 = 0.1089 ± 0.0011GeV2 Araw = -1.418 ppm 0.105 ppm (stat)

  22. HAPPEX-II Q2=0.091 GeV2 Q2=0.099 GeV2 Q2=0.077 GeV2 Q2=0.109 GeV2 Example: The window pair statistical error is 620 ppm for 2004 HAPPEX-H.

  23. Recent Happex Publications – 2004 runs Phys.Rev. Lett. 96, 022003 (2006) Parity-Violating Electron Scattering from 4He and the Strange Electric Form Factor fo the Nucleon GEs = -0.038 0.042(stat) 0.010(syst) Phys. Lett. B635 (2006) 275 Constraints on the Nucleon Strange Form Factors at Q2 0.1 GeV2 GEs + 0.080GMs = 0.030 0.025(stat) 0.006(syst) 0.012(FF)

  24. Extrapolated from G0 Q2=[0.12,0.16] GeV2 Dc2 = 1 95% c.l. Theory Calculations 16. Skyrme Model - N.W. Park and H. Weigel, Nucl. Phys. A 451, 453 (1992). 17. Dispersion Relation - H.W. Hammer, U.G. Meissner, D. Drechsel, Phys. Lett. B 367, 323 (1996). 18. Dispersion Relation - H.-W. Hammer and Ramsey-Musolf, Phys. Rev. C 60, 045204 (1999). 19. Chiral Quark Soliton Model - A. Sliva et al., Phys. Rev. D 65, 014015 (2001). 20. Perturbative Chiral Quark Model - V. Lyubovitskij et al., Phys. Rev. C 66, 055204 (2002). 21. Lattice - R. Lewis et al., Phys. Rev. D 67, 013003 (2003). 22. Lattice + charge symmetry -Leinweber et al, Phys. Rev. Lett. 94, 212001 (2005) & hep-lat/0601025 19 21 22 16 17 18

  25. HAPPEX-II 2005 Preliminary Results HAPPEX-4He: Q2 = 0.0772 ± 0.0007 (GeV/c)2 APV = +6.43  0.23 (stat)  0.22 (syst) ppm A(Gs=0) = +6.37 ppm GsE = 0.004  0.014(stat)  0.013(syst) HAPPEX-H: Q2 = 0.1089 ± 0.0011 (GeV/c)2 APV = -1.60  0.12 (stat)  0.05 (syst) ppm A(Gs=0) = -1.640 ppm 0.041 ppm GsE + 0.088 GsM = 0.004  0.011(stat)  0.005(syst)  0.004(FF)

  26. HAPPEX-II 2005 Preliminary Results • Three bands: • Inner: Project to axis for 1-D error bar • Middle: 68% probability contour • Outer: 95% probability contour Preliminary HAPPEX 2005 data Caution: the combined fit is approximate. Correlated errors and assumptions not taken into account

  27. World data confronts theoretical predictions 16. Skyrme Model - N.W. Park and H. Weigel, Nucl. Phys. A 451, 453 (1992). 17. Dispersion Relation - H.W. Hammer, U.G. Meissner, D. Drechsel, Phys. Lett. B 367, 323 (1996). 18. Dispersion Relation - H.-W. Hammer and Ramsey-Musolf, Phys. Rev. C 60, 045204 (1999). 19. Chiral Quark Soliton Model - A. Sliva et al., Phys. Rev. D 65, 014015 (2001). 20. Perturbative Chiral Quark Model - V. Lyubovitskij et al., Phys. Rev. C 66, 055204 (2002). 21. Lattice - R. Lewis et al., Phys. Rev. D 67, 013003 (2003). 22. Lattice + charge symmetry -Leinweber et al, Phys. Rev. Lett. 94, 212001 (2005) & hep-lat/0601025 Preliminary results from 2005 data

  28. A simple picture of GEs – Scattering from a group of randomly oriented electric dipoles formed by the pairs. Average over cross sections and deduce <GES>. beam 1/3 e q In this simple picture the dipoles would have a separation of 2a 0.014F if GES = 0.004. a a -1/3 e qBreit = 1.594 F-1, for HAPPEX-II data

  29. Strange form factors of the proton A recent fit to the world’s data for Q2<0.3GeV2 R. D. Young et al., nucl-ex/0604010 GEs = rsQ2. rs = -0.06 0.41 GeV2 GMs = ms. ms = 0.12 0.55 0.07 Includes data from SAMPLE, PVA4, G0, HAPPEX (2004) Lattice QCD calculation of GMs D. B. Leinweber et al., PRL 94(2005)212001 GMs = (-0.046 0.019)mn QNP06 – A. W. Thomas, HAPPEX II result plus Leinweber calculation means contribute 10 MeV or less to the nucleon’s mass.

  30. G0 backward HAPPEX-III GEs 0.6 GeV2 GMs Summary Preliminary Preliminary • Suggested large values at Q2~0.1 GeV2 • Ruled out • Large possible cancellation at Q2~0.2 GeV2 • Very unlikely given constraint at 0.1 GeV2 • G0 back angle at low Q2 (error bar~1.5% of mp) maintains sensitivity to discover GMS • Possible large values at Q2>0.4 GeV2 • G0 backangle, finished Spring 2007 • HAPPEX-III - 2008

  31. References mrst2004 Ann. Rev. Nucl. Part. Sci. 2001. 51:189-217, D. Beck, R. McKeown

  32. Relative probabiliity for transition is circled

  33. Detailed Formulae: Clean Probe of StrangenessInside the Nucleon Hydrogen • Measurement of APV yields linear combination of GsE, GsM 4He • Sensitive only to GsE

  34. Backward angle Forward angle Parity-violating electron scattering For a proton: ~ few parts per million For 4He:GEs alone(but only available at low Q2) For deuterium: enhanced GAe sensitivity

  35. 2 g g Z0 PV Electron Scattering to Measure Weak NC Amplitudes Interference with EM amplitude makes NC amplitude accessible

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