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Spin Structure with JLab 6 and 12 GeV

Spin Structure with JLab 6 and 12 GeV. J. P. Chen, Jefferson Lab INT-12-49W: Workshop on Orbital Angular Momentum in QCD, Feb. 6, 2011. Overview Selected Results from JLab 6 GeV A 1 at High-x: Valence Quark Spin Distributions Moments

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Spin Structure with JLab 6 and 12 GeV

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  1. Spin Structure with JLab 6 and 12 GeV J. P. Chen, Jefferson Lab INT-12-49W: Workshop on Orbital Angular Momentum in QCD, Feb. 6, 2011 • Overview • Selected Results from JLab 6 GeV • A1 at High-x: Valence Quark Spin Distributions • Moments • g2 /d2: B-C Sum Rule, Color Lorentz Force (Polarizability) • SIDIS: Transversity and Flavor Decomposition • Planned experiments with JLab 12 GeV

  2. Introduction • Spin experiments provide fundamental information as well as insights into QCD dynamics • Experiments: polarized beams(e, p), polarized targets (p, d, 3He/n) longitudinal and transverse target polarization A||, A|_ A1, A2 Ds||, Ds|_ Spin Structure Functions g1(x, Q2), g2(x, Q2) Role of unpolarized PDFs/ R • Polarized PDFs Dq(x) LO, NLO,…, QCD evolution, Higher-twists • Moments, sum rules • High-x, low-x • World data (CERN, SLAC, HERMES, RHIC-spin, JLab, …) • JLab 6 GeV: high-x, low Q2, high-precision. , • Future :12 GeV

  3. Jefferson Lab Experimental Halls 6 GeV polarized CW electron beam Pol=85%, 200mA Will be upgraded to 12 GeV by ~2014 HallA: two HRS’ Hall B:CLAS Hall C: HMS+SOS

  4. JLab Polarized Proton/Deuteron Target • Polarized NH3/ND3 targets • Dynamical Nuclear Polarization • In-beam average polarization 70-90% for p 30-50% for d • Luminosity ~ 1035 (Hall C/A) ~ 1034 (Hall B)

  5. JLab Polarized 3He Target • longitudinal, transverse and vertical • Luminosity=1036 (1/s) (highest in the world) • Record high pol ~ 60% 60% 15 uA

  6. add Hall D (and beam line) 12 Upgrade magnets and power supplies CHL-2 Enhance equipment in existing halls 6 GeV JLab

  7. Experimental Halls (new) Hall D: linear polarized photon beam, Selonoid detetcor GluoX collaboration: exotic meson spectroscopy gluon-quark hybrid, confinement Hall B: CLAS12 GPDs, TMDs, … Hall C: Super HMS + existing HMS Form factors, structure functions (A1n/d2n), … Hall A: Dedicated devices + existing spectrometers Super BigBite, SoLID, MOLLER SIDIS (transversity/TMDs), PVDIS, …

  8. JLab Spin Experiments • Results: Published and Preliminary/Upcoming • Spin in the valence (high-x) region • Spin (g1/g2) Moments: Spin Sum Rules, d2 • SSA in SIDIS: Transversity (n) • SSA in Inclusive Reaction • On-going • g2pat low Q2 • Future: 12 GeV • Inclusive: A1/d2, • Semi-Inclusive: Transversity, Flavor-decomposition • Reviews: S. Kuhn, J. P. Chen, E. Leader, Prog. Part. Nucl. Phys. 63, 1 (2009)

  9. Valence Quark Spin Structure A1 at high x and flavor decomposition

  10. Why Are PDFs at High x Important? • Valence quark dominance: simpler picture -- direct comparison with nucleon structure models SU(6) symmetry, broken SU(6), diquark • x 1 region amenable to pQCD analysis -- hadron helicity conservation? role of quark orbit angular momentum? • Clean connection with QCD, via lattice moments (d2) • Input for search for new physics at high energy collider -- evolution: high x at low Q2 low x at high Q2 -- small uncertainties amplified -- example: HERA ‘anomaly’ (1998)

  11. World data for A1 Proton Neutron

  12. JLab E99-117Precision Measurement of A1nat Large x Spokespersons: J. P. Chen, Z. Meziani, P. Souder; PhD Student: X. Zheng • First precision A1n data at high x • Extracting valence quark spin distributions • Test our fundamental understanding of valence quark picture • SU(6) symmetry • Valence quark models • pQCD (with HHC) predictions • Quark orbital angular momentum • Crucial input for pQCD fit to PDF • PRL 92, 012004 (2004) • PRC 70, 065207 (2004)

  13. Polarized Quark Distributions • Combining A1n and A1p results • Valence quark dominating at high x • u quark spin as expected • d quark spin stays negative! • Disagree with pQCD model calculations assuming HHC (hadron helicity conservation) • Quark orbital angular momentum • Consistent with valence quark models and pQCD PDF fits without HHC constraint

  14. pQCD with Quark Orbital Angular Momentum H. Avakian, S. Brodsky, A. Deur, and F. Yuan, PRL 99, 082001 (2007) Inclusive Hall A and B and Semi-Inclusive Hermes BBS BBS+OAM

  15. Preliminary A1(p) Results, Hall C SANE Spokespersons: S. Choi, M. Jones, Z. Meziani and O. Rondon Courteous of O. Rondon

  16. Preliminary A1(3He) Results, Hall A E06-014 Spokespersons: S. Choi, Z. Meziani, X. Jiang and B. Sawasky Courteous of D. Flay

  17. Spin-Structure in Resonance Region: E01-012 Spokesperson: N. Liyanage, J. P. Chen, S. Choi;PhD Student: P. Solvignon PRL 101, 1825 02 (2008) A13He (resonance vs DIS) G1 resonance vs. pdfs x Q2 x

  18. Projections for JLab at 11 GeV A1p at 11 GeV (CLAS12) A1n at 11 GeV (Hall C/A)

  19. Flavor decomposition with SIDIS JLab @11 GeV Du and Dd at JLab 11 GeV Polarized Sea

  20. p multiplicities in SIDIS ep→e’pX Hall-C CLAS 6 DSS (Q2=2.5GeV2) DSS (Q2=25GeV2)

  21. Moments of Spin Structure Functions Sum Rules, Polarizabilities

  22. First Moment of g1p:G1p Total Quark Contribution to Proton Spin (at high Q2) Twist expansion at intermediate Q2, LQCD, ChPT at low Q2 G1p EG1b, arXiv:0802.2232 EG1a, PRL 91, 222002 (2003) Spokespersons: V. Burkert, D. Crabb, G. Dodge,

  23. First Moment of g1n:G1n G1n E94-010, PRL 92 (2004) 022301 E97-110, preliminary EG1a, from d-p

  24. G1 of p-n EG1b, PRD 78, 032001 (2008) E94-010 + EG1a: PRL 93 (2004) 212001

  25. Second Spin Structure Function g2 Burkhardt - Cottingham Sum Rule d2: Color Lorentz Force (Polarizability) Spin Polarizabilities

  26. Precision Measurement of g2n(x,Q2): Search for Higher Twist Effects • Measure higher twist quark-gluon correlations. • Hall A Collaboration, K. Kramer et al., PRL 95, 142002 (2005)

  27. BC Sum Rule 0<X<1 :Total Integral P Brawn: SLAC E155x Red: Hall C RSS Black: Hall A E94-010 Green: Hall A E97-110(preliminary) Blue: Hall A E01-012 (spokespersons: N. Liyanage, former student, JPC) (preliminary) N BC = Meas+low_x+Elastic “Meas”: Measured x-range 3He • “low-x”: refers to unmeasured low x part • of the integral. • Assume Leading Twist Behaviour very prelim Elastic: From well know FFs (<5%)

  28. BC Sum Rule P BC satisfied w/in errors for JLab Proton 2.8 violation seen in SLAC data N BC satisfied w/in errors for Neutron (But just barely in vicinity of Q2=1!) 3He very prelim BC satisfied w/in errors for 3He

  29. Color Lorentz Force (Polarizability): d2 • 2nd moment of g2-g2WW • d2: twist-3 matrix element d2 and g2-g2WW: clean access of higher twist (twist-3) effect:q-g correlations Color polarizabilities cE,cB are linear combination of d2 and f2 Provide a benchmark test of Lattice QCD at high Q2 Avoid issue of low-x extrapolation Relation to Sivers and other TMDs

  30. d2(Q2) E08-027 “g2p” SANE 6 GeV Experiments Sane: new in Hall C “g2p” in Hall A, 2011 projected “d2n” new in Hall A

  31. Preliminary results on neutron from E01-012Spokespersons: J. P. Chen, S. Choi, N. Liyanage, plots by P. Solvignon

  32. Preliminary A2(p) Results, Hall C SANE Spokespersons: S. Choi, M. Jones, Z. Meziani and O. Rondon Courteous of O. Rondon

  33. Projection on d2p from Hall C SANE

  34. Projection on Hall A E06-014 (d2n) Spokespersons: S. Choi, Z. Meziani, X. Jiang and B. Sawasky Courteous of D. Flay

  35. E08-027 : Proton g2 Structure Function Fundamental spin observable has never been measured at low or moderate Q2 Spokespersons: A. Camsonne, J. P. Chen, D. Crabb, K. Slifer, 6 PhD students • BC Sum Rule : violation suggested for proton at large Q2,but found satisfied for the neutron & 3He. • Spin Polarizability: Major failure (>8s) of PT for neutron dLT. Need g2 isospinseparation to solve. • Hydrogen HyperFine Splitting : Lack of knowledge of g2 at low Q2 is one of the leading uncertainties. • Proton Charge Radius : also one of the leading uncertainties in extraction of <Rp> from m-H Lamb shift. Scheduled to run 2/2012-5/2012 BC Sum Rule Spin Polarizability LT

  36. Spin Polarizabilities Preliminary E97-110 (and Published E94-010)Spokesperson: J. P. Chen, A. Deur, F. Garibaldi, plots by V. Sulkosky • Significant disagreement between data and both ChPT calculations for dLT • Good agreement with MAID model predictions g0dLT Q2 Q2

  37. Single Target-Spin Asymmetries in SIDIS Transversity/Tensor Charge

  38. Transversity • Three twist-2 quark distributions: • Momentum distributions: q(x,Q2) = q↑(x) + q↓(x) • Longitudinal spin distributions: Δq(x,Q2) = q↑(x) - q↓(x) • Transversity distributions: δq(x,Q2) = q┴(x) - q┬(x) • It takes two chiral-odd objects to measure transversity • Semi-inclusive DIS Chiral-odd distributions function(transversity) Chiral-odd fragmentation function(Collins function)

  39. E06-010 3He Target Single-Spin Asymmetry in SIDISSpokespersons: J. P. Chen, E. Cisbani, H. Gao, X. Jiang, J-C. Peng, 7 PhD students X. Qian, et al. PRL (2011) 3He Collins SSA small Non-zero at highest x for p+ 3He Sivers SSA: negative for π+, Blue band: model (fitting) uncertainties Red band: other systematic uncertainties

  40. Results on Neutron Collins asymmetries are not large, except at x=0.34 Sivers negative Blue band: model (fitting) uncertainties Red band: other systematic uncertainties

  41. 12 GeV: Mapping of Collins Asymmetries with SoLID E12-10-006 3He(n), Spokespersons: J. P. Chen, H. Gao, X. Jiang, J-C. Peng, X. QianE12-11-007(p) , Spokespersons: K. Allda, J. P. Chen, H. Gao, X. Li, Z-E. Mezinai • Both p+ and p- • For one z bin (0.4-0.45) • Will obtain many z bins (0.3-0.7) • Tensor charge

  42. Summary • Spin structure study full of surprises and puzzles • A decade of experiments from JLab: exciting results • valence spin structure • precision measurements of g2/d2: high-twist • spin sum rules and polarizabilities • first neutron transversity • Bright future • 12 GeV Upgrade will greatly enhance our capability • Precision determination of the valence quark spin structure flavor separation • Precision measurements of g2/d2 • Precision extraction of transversity/tensor charge

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