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

2. Recent Talks by the HAPPEX Collaboration 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)PPT TJNAF Seminar: Results from the 2005 HAPPEX-II Run, 21 April 2006 - Kent Paschke (PPT)PPT See these talks for greater detail 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 Molecules =  atoms, mass molecule =  mass atoms Atom =  (nuclei + electrons), m atom =m nuclei +m electrons Nucleus =  nucleons, m nucleus Zm p +Nm n Nucleon=  quarks+gluons), m nucleon m quarks ! A hierarchy of structures

4. From PDG, m u is 1.5 to 4 MeV m d is 4 to 8 MeV Proton flavor content is uud, m p 2m u + m d Example of origin of proton’s mass, PRL 74 (1071) 1995, X. Ji Quark kinetic + potential energy = 1/3 m nucleon Total gluon energy = 7/12 m nucleon Quark masses = 1/12 m nucleon 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 qcqc qcqc A constituent u quark has spin ½ and is a dynamical system. ucuc g ucuc

6. 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: Are strange sea quarks present in the nucleon?

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

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

9. I 3 weak isospin Q electric charge q v vector a axial q a axialvector u1/22/3½ - 4/3sin 2  w 1/2 d-1/2-1/3-½ + 2/3sin 2  w -1/2 -1/3-½ + 2/3sin 2  w -1/2 Electroweak coupling constants s e -1/2 -1/2 + 2sin 2  W -1/2

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

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

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

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

14. Jefferson Laboratory Polarized e - Source Hall A Continuous Electron Beam Accelerator Facility CEBAF Features: 1.Polarized Source 2.Quiet Accelerator 3.Precision Spectrometers in Hall A

15. 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 1998-99: Q 2 =0.5 GeV 2, 1 H 2004-06: Q 2 =0.1 GeV 2, 1 H, 4 He 2008:Q 2 =0.6, 1 H HAPPEX Experiment

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

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

18. High-Power Cryogenic Target New "race track" design – 20 cm (transverse cryogen flow) CSULA design and fabrication. 20 cm 1.8% R.L. LH 2 20 cm 2.2% R.L. 4 He gas cell –Cold (6.6K), dense (230 psi) Al wall thickness –4 mils (H) –10 mils (He)

19. controls effective analyzing power Tune residual linear pol. Slow helicity reversal Intensity Attenuator (charge Feedback) Polarized Source High P e High Q.E. Low A power 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

20. 4 He Preliminary Results Q 2 = 0.07725 ± 0.0007 GeV 2 A raw = 5.253 ppm  0.191 ppm (stat) Raw Parity Violating Asymmetry Helicity Window Pair Asymmetry 35 M pairs, total width ~1130 ppm A raw correction ~ 0.12 ppm Slug Asymmetry (ppm)

21. 1 H Preliminary Results Q 2 = 0.1089 ± 0.0011GeV 2 A raw = -1.418 ppm  0.105 ppm (stat) A raw correction ~11 ppb Raw Parity Violating Asymmetry Helicity Window Pair Asymmetry ~25 M pairs, width ~540 ppm Asymmetry (ppm) Slug

22. June 2004 HAPPEX-He about 3M pairs at 1300 ppm =>  A stat ~ 0.74 ppm June – July 2004 HAPPEX-H about 9M pairs at 620 ppm =>  A stat ~ 0.2 ppm July-Sept 2005 HAPPEX-He about 35M pairs at 1130 ppm =>  A stat ~ 0.19 ppm Oct – Nov 2005 HAPPEX-H about 25M pairs at 540 ppm =>  A stat ~ 0.105 ppm HAPPEX-II Q 2 =0.091 GeV 2 Q 2 =0.099 GeV 2 Q 2 =0.077 GeV 2 Q 2 =0.109 GeV 2 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 4 He and the Strange Electric Form Factor fo the Nucleon G E s = -0.038 0.042(stat) 0.010(syst) Constraints on the Nucleon Strange Form Factors at Q 2 0.1 GeV 2 Phys. Lett. B635 (2006) 275 G E s + 0.080G M s = 0.030 0.025(stat) 0.006(syst) 0.012(FF)

24. Extrapolated from G0 Q 2 =[0.12,0.16] GeV 2 95% c.l.  2 = 1 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 18 17 16 19 21 22

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

26. HAPPEX-II 2005 Preliminary Results Three bands: 1.Inner: Project to axis for 1-D error bar 2.Middle: 68% probability contour 3.Outer: 95% probability contour Caution: the combined fit is approximate. Correlated errors and assumptions not taken into account Preliminary HAPPEX 2005 data

27. World data confronts theoretical predictions Preliminary results from 2005 data 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

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

29. A recent fit to the world’s data for Q 2 <0.3GeV 2 R. D. Young et al., nucl-ex/0604010 G E s =  s Q 2.  s = -0.06 0.41 GeV 2 G M s =  s.  s = 0.12 0.55 0.07 Strange form factors of the proton Includes data from SAMPLE, PVA4, G0, HAPPEX (2004) Lattice QCD calculation of G M s D. B. Leinweber et al., PRL 94(2005)212001 G M s = (-0.046 0.019)  n QNP06 – A. W. Thomas, HAPPEX II result plus Leinweber calculation means contribute 10 MeV or less to the nucleon’s mass.

30. Summary Suggested large values at Q 2 ~0.1 GeV 2 Ruled out Possible large values at Q 2 >0.4 GeV 2 G 0 backangle, finished Spring 2007 HAPPEX-III - 2008 Large possible cancellation at Q 2 ~0.2 GeV 2 Very unlikely given constraint at 0.1 GeV 2 G0 back angle at low Q 2 (error bar~1.5% of  p ) maintains sensitivity to discover G M S Preliminary 0.6 GeV 2 G0 backward HAPPEX-III GMsGMs GEsGEs Preliminary

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

35. Relative probabiliity for transition is circled

37. Detailed Formulae: Clean Probe of Strangeness Inside the Nucleon Measurement of A PV yields linear combination of G s E, G s M Sensitive only to G s E Hydrogen 4 He

38. Parity-violating electron scattering ~ few parts per million For a proton: For 4 He: G E s alone (but only available at low Q 2 ) Forward angle Backward angle For deuterium: enhanced G A e sensitivity

39. PV Electron Scattering to Measure Weak NC Amplitudes Interference with EM amplitude makes NC amplitude accessible  Z0Z0  2