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Highlights of Spin Study at JLab Hall A: Longitudinal and Transverse

Highlights of Spin Study at JLab Hall A: Longitudinal and Transverse. J. P. Chen, Jefferson Lab Pacific-Spin2011 , Cairns, Australia. Introduction Longitudinal and transverse spin Selected results from JLab Hall A SSA in SIDIS: Transversity and TMDs

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Highlights of Spin Study at JLab Hall A: Longitudinal and Transverse

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  1. Highlights of Spin Study at JLab Hall A: Longitudinal and Transverse J. P. Chen, Jefferson Lab Pacific-Spin2011, Cairns, Australia • Introduction • Longitudinal and transverse spin • Selected results from JLab Hall A • SSA in SIDIS: Transversity and TMDs • g2 (d2) at intermediate to high Q2: higher-twists, B-C sum rule • g1/g2 at low Q2: GDH sum/spin polarizabilities • Future experiments (6 GeV and 12 GeV)

  2. Spin Milestones (I) • Nature: (www.nature.com/milestones/milespin) • 1896: Zeeman effect (milestone 1) • 1922: Stern-Gerlach experiment (2) • 1925: Spinning electron (Uhlenbeck/Goudsmit)(3) • 1928: Dirac equation (4) • Quantum magnetism (5) • 1932: Isospin(6) • 1935: Proton anomalous magnetic moment • 1940: Spin–statistics connection(7) • 1946: Nuclear magnetic resonance (NMR)(8) • 1950s: Development of magnetic devices (9) • 1950-51: NMR for chemical analysis (10) • 1951: Einstein-Podolsky-Rosen argument in spin variables(11) • 1964: Kondo Effect (12) • 1971: Supersymmetry(13) • 1972:Superfluid helium-3 (14)

  3. Spin Milestones (II) • 1973: Magnetic resonance imaging(15) • 1975-76:NMR for protein structure determination (16) • 1978: Dilute magnetic semiconductors (17) • 1980s: “Proton spin crisis or puzzle” • 1988: Giant magnetoresistance(18) • 1990: Functional MRI (19) • Proposal for spin field-effect transistor (20) • 1991: Magnetic resonance force microscopy (21) • 1996: Mesocopic tunnelling of magnetization (22) • 1997: Semiconductor spintronics (23) • (Spin-polarized suprecurrents for spintronics, 1/2011) • 2000s: “Nucleon transverse spin puzzle”? • ?: More puzzles in nucleon spin? • …… • ?: Breakthroughs in nucleon spin/nucleon structure study? • …… • ?: Applications of nucleon spin physics?

  4. Nucleon Structure, Moments and Sum Rules • Global properties and structure Mass: 99% of the visible mass in universe ~1 GeV, but u/d quark mass only a few MeV each! Momentum: quarks carry ~ 50% Energy-Momentum Sum Rule Spin: ½, quarks contribution ~30% Spin Sum Rule(s) Magnetic moment: large part anomalous, >150% GDH Sum Rule Axial charge Bjorken Sum Rule Angular momentum Ji’s Sum Rule Polarizabilities (Spin, Color) Tensor charge

  5. Three Decades of Spin Structure Study • 1980s: EMC (CERN) + early SLAC quark contribution to proton spin is very small DS = (12+-9+-14)% !‘spin crisis’ (Ellis-Jaffe sum rule violated) • 1990s: SLAC, SMC (CERN), HERMES (DESY) DS = 20-30% the rest: gluon and quark orbital angular momentum A+=0 (light-cone) gauge(½)DS + Lq+ DG + Lg=1/2 (Jaffe) gauge invariant (½)DS + Lq + JG =1/2 (Ji) A new decomposition (X. Chen, et. al) What observable directly corresponds to Lz~ bx X py ? Bjorken Sum Rule verified to <10% level • 2000s: COMPASS (CERN), HERMES, RHIC-Spin, JLab, … : • DS ~ 30%; DGprobably small,orbital angular momentum probably significant • Sum Rules at low Q2 • Higher-Twists • Transversity, Transverse-Momentum Dependent Distributions

  6. Jefferson Lab Experimental Halls 6 GeV polarized CW electron beam Pol=85%, 180mA Will be upgraded to 12 GeV by ~2014 HallA: two HRS’ Hall B:CLAS Hall C: HMS+SOS

  7. JLab Polarized 3He Target • longitudinal, transverse and vertical • Luminosity=1036 (1/s) (highest in the world) • High in-beam polarization ~ 60% • Effective polarized neutron target • 13 completed experiments 7 approved with 12 GeV (A/C) 15 uA

  8. JLab Polarized Proton/Deuteron Target • Polarized NH3/ND3 targets • Dynamical Nuclear Polarization • In-beam average polarization 70-90% for p 30-40% for d • Luminosity up to ~ 1035 (Hall C/A) ~ 1034 (Hall B)

  9. JLab Spin Experiments • Results: • SSA in SIDIS: Transversity (n)/ TMDs • g2/d2: Higher twists, B-C sum rule • Spin Moments: Spin Sum Rules and Polarizabilities • Quark-Hadron duality • Spin in the valence (high-x) region • Planned • g2pat low Q2 • Future: 12 GeV • Inclusive: A1/d2, • Semi-Inclusive: Transversity, TMDs, Flavor-decomposition • Review: Sebastian, Chen, Leader, arXiv:0812.3535, PPNP 63 (2009) 1

  10. Single Target-Spin Asymmetries in SIDIS Transversity and TMDs

  11. 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) • TMDs: (without integrating over PT) • Distribution functions depends on x, k┴ and Q2 : δq, f1T┴ (x,k┴,Q2), … • Fragmentation functions depends on z, p┴ and Q2 : D, H1(x,p┴,Q2) • Measured asymmetries depends on x, z, P┴ and Q2 : Collins, Sivers, … (k┴, p┴ and P┴ are related)

  12. Nucleon Spin Quark Spin Leading-Twist TMD PDFs h1= Boer-Mulders f1 = h1L= Worm Gear (Kotzinian-Mulders) Helicity g1 = h1= Transversity f1T= g1T= h1T= Sivers Worm Gear Pretzelosity : Survive trans. Momentum integration

  13. Leading-Twist TMD PDFs Nucleon Spin Quark Spin h1= Boer-Mulders f1 = h1L= Worm Gear (Kotzinian-Mulders) Helicity g1 = h1= Transversity f1T= g1T= h1T= Sivers Worm Gear Pretzelosity : Probed by E06-010

  14. Separation of Collins, Sivers and pretzelocity effects through angular dependence

  15. Current Status Large single spin asymmetry in pp->pX Collins Asymmetries - sizable for proton (HERMES and COMPASS) large at high x, p- and p+ has opposite sign unfavored Collins fragmentation as large as favored (opposite sign)? - consistent with 0 for deuteron (COMPASS) Sivers Asymmetries - non-zero for p+ from proton (HERMES), consistent with zero (COMPASS)? - consistent with zero for p- from proton and for all channels from deuteron - large for K+ ? Very active theoretical and experimental study RHIC-spin, JLab (Hall A 6 GeV, CLAS12, HallA/C 12 GeV), Belle, FAIR (PAX) Global Fits/models by Anselmino et al., Yuan et al. and … First neutron measurement from Hall A 6 GeV (E06-010) Solenoid with polarized 3He at JLab 12 GeV Unprecedented precision with high luminosity and large acceptance

  16. E06‑010 Experiment Luminosity Monitor • First measurement on n (3He) • Polarized 3He Target • Polarized Electron Beam, 5.9 GeV • ~80% Polarization • Fast Flipping at 30Hz • BigBite at 30º as Electron Arm • Pe = 0.7 ~ 2.2 GeV/c • HRSL at 16º as Hadron Arm • Ph = 2.35 GeV/c • Excellent PID for p/K/p • 7 PhD Thesis Students (5 graduated) Beam Polarimetry (Møller + Compton)

  17. Performance of 3He Target • High luminosity: L(n) = 1036 cm-2 s-1 • Record high in-beam~ 60% polarization with 15 A beam with automatic spin flip every 20 minutes History of Figure of Merit of Polarized 3He Target In-beam 3He pol. 55-60%

  18. 3He Target Single-Spin Asymmetry in SIDIS arXiv: 1106.0363, submitted to PRL 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

  19. 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

  20. Asymmetry ALT Result • 3He ALT Positive for p- Preliminary To leading twist:

  21. Neutron ALT Extraction • Corrected for proton dilution, fp • Predicted proton asymmetry contribution < 1.5% (π+), 0.6% (π-) • Dominated by L=0 (S) and L=1 (P) interference • Consist w/ model in signs, suggest larger asymmetry Preliminary

  22. JLab 12 GeV Era: Precision Study of TMDs From exploration to precision study with 12 GeV JLab Transversity: fundamental PDFs, tensor charge TMDs: 3-d momentum structure of the nucleon  Quark orbital angular momentum Multi-dimensional mapping of TMDs 4-d (x,z,P┴,Q2) Multi-facilities, global effort Precision  high statistics high luminosity and large acceptance

  23. Solenoid detector for SIDIS at 11 GeV Also for PVDIS at 11 GeV • Approved SIDIS experiments: • E10-006 & E11-007 • SSA in SIDIS Pion Production Transversely/ Longitudinally Polarized 3He Target • at 8.8 and 11 GeV. • Large acceptance: >100 msr • High luminosity : > 1036

  24. Mapping of Collins/Siver Asymmetries with SoLID • Both p+ and p- • For one z bin (0.4-0.45) • Will obtain many z bins (0.3-0.7) • Upgraded PID for K+ and K-

  25. Map Collins and Sivers asymmetries in 4-D (x, z, Q2, PT)

  26. Worm-gear functions: h1L= • Dominated by real part ofinterference between L=0 (S) and L=1 (P) states • No GPD correspondence • Lattice QCD -> Dipole Shift in mom. space. • Model Calculations -> h1L =? -g1T. Worm Gear Center of points: g1T=

  27. Discussion Unprecedented precision 4-d mapping of SSA Collins and Sivers p+, p- and K+, K- New proposal polarized proton with SoLID Study factorization with x and z-dependences Study PT dependence Combining with the world data extract transversity and fragmentation functions for both u and d quarks determine tensor charge study TMDs for both valence and sea quarks study quark orbital angular momentum study Q2 evolution Global efforts (experimentalists and theorists), global analysis much better understanding of multi-d nucleon structure and QCD Longer-term future: EIC to map sea and gluon SSAs

  28. Inclusive Transverse Spin g2 Structure Function and Moments Burkhardt - Cottingham Sum Rule

  29. g2: twist-3, q-g correlations • experiments: transversely polarized target SLAC E155x, (p/d) JLab Hall A (n), Hall C (p/d) • g2 leading twist related to g1 by Wandzura-Wilczek relation • g2 - g2WW: a clean way to access twist-3 contribution • quantify q-g correlations

  30. 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)

  31. 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 (very 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%)

  32. 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

  33. Results on G2n : E01-012 and E94-010

  34. Higher-Twist Extraction and Comparison Extract Higher-Twist part of G2DIS Compare with higher-twist estimated from E97-103 data

  35. Color Polarizability (Lorentz Force): 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

  36. Measurements on neutron: d2n

  37. 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

  38. Spin Sum Rules: Moments of SFs Sum Rules Moments of Spin Structure Functions  Global Property

  39. Generalized GDH Sum RuleConnecting GDH with Bjorken Sum Rules • Q2-evolution of GDH Sum Rule provides a bridge linking strong QCD to pQCD • Bjorken and GDH sum rules are two limiting cases High Q2, Operator Product Expansion : S1(p-n) ~ gA  Bjorken Q2  0, Low Energy Theorem: S1 ~ k2  GDH • High Q2 (> ~1 GeV2): Operator Product Expansion • Intermediate Q2 region: Lattice QCD calculations • Low Q2 region (< ~0.1 GeV2): Chiral Perturbation Theory Calculations: HBcPT: Ji, Kao, Osborne, Spitzenberg, Vanderhaeghen RBcPT: Bernard, Hemmert, Meissner Reviews: Chen, Deur, Meziani, Mod. Phy. Lett. A 20, 2745 (2005) J.P. Chen, Int. J. Mod. Phys. E19, 1893 (2010).

  40. JLab E94-010 and E97-110Genaralized GDH sum on neutron at Low Q2 E94-010 E97-110 0.1 < Q2 < 1 GeV2, resonance region 0.02 < Q2 < 0.3 GeV2, resonance region PRL 89 (2002) 242301 Q2 Q2

  41. First Moment of g1p:G1p Test fundamental understanding ChPT at low Q2, Twist expansion at high Q2, Future Lattice QCD G1p EG1b, arXiv:0802.2232 EG1a, PRL 91, 222002 (2003)

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

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

  44. Effective Coupling Extracted from Bjorken Sum A. Deur, V. Burkert, J. P. Chen and W. Korsch PLB 650, 244 (2007) and PLB 665, 349 (2008) as/p

  45. Spin Polarizabilities Higher Moments of Spin Structure Functions at Low Q2

  46. Higher Moments: Generalized Spin Polarizabilities • generalized forward spin polarizability g0 generalized L-T spin polarizability dLT

  47. Neutron Spin Polarizabilities • dLT insensitive to D resonance • RB ChPT calculation with resonance for g0 agree with data at Q2=0.1 GeV2 • Significant disagreement between data and both ChPT calculations for dLT • Good agreement with MAID model predictions g0dLT E94-010, PRL 93 (2004) 152301 Q2 Q2

  48. Preliminary Results from E97-110 • Significant disagreement between data and both ChPT calculations for dLT • Good agreement with MAID model predictions g0dLT Q2 Q2

  49. Axial Anomaly and the LTPuzzle N. Kochelev and Y. Oh; arXiv:1103.4891v1

  50. E08-027 : Proton g2 Structure Function Fundamental spin observable has never been measured at low or moderate Q2 Spokespersons: Camsonne, Crabb, Chen, Slifer(contact), 6 PhD students, 3 postdocs • 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 11/2011-5/2012 BC Sum Rule Spin Polarizability LT

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