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Single Spin Asymmetries and Transverse Structure of the Nucleon

Single Spin Asymmetries and Transverse Structure of the Nucleon. Jian -ping Chen ( 陈剑平 ) , Jefferson Lab, Virginia, USA Seminar @ USTC, Hefei, China, July 9, 2013. Introduction Recent SSA Results from JLab New Preliminary SSA Results from JLab

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Single Spin Asymmetries and Transverse Structure of the Nucleon

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  1. Single Spin Asymmetries and Transverse Structure of the Nucleon Jian-ping Chen (陈剑平), Jefferson Lab, Virginia, USA Seminar @ USTC, Hefei, China, July 9, 2013 • Introduction • Recent SSA Results from JLab • New Preliminary SSA Results from JLab • TMD study with SoLID at JLab 12 GeV • SoLID Program on SSA/TMDs • Long-term Future: TMDs study with Electron-Ion Colliders (EIC) • MEIC@ JLab and E-RHIC@BNL • A New Opportunity: an EIC in China (EIC@HIAF)

  2. Introduction Strong QCD, Nucleon Structure/TMDs

  3. What Are the Challenges? • Success of the Standard Model Recent discovery of Higgs particle Electro-Weak theory tested to very good level of precision Strong interaction theory (QCD) tested in the high energy (short distance) region • Major challenges: Understand QCD in the strong region (distance of the nucleon size) Understand quark-gluon structure of the nucleon Confinement • Beyond Standard Model Energy frontier – LHC search: no new physics (yet) Precision tests of Standard Model at low energy Precision information of nucleon structure needed

  4. QCD: Unsolved in Nonperturbative Region running coupling “constant” • 2004 Nobel prize for ``asymptotic freedom’’ • non-perturbative regime QCD confinement • Nature’s only known truly nonperturbative fundamental theory • One of the top 10 challenges for physics! • QCD: Important for discovering new physics beyond SM • Nucleon: stable lab to study QCD • Nucleon structure is one of the most active areas

  5. Electron Scattering and Nucleon Structure • Clean probe to study nucleon structure only electro-weak interaction, well understood • Elastic Electron Scattering: Form Factors  60s: established nucleon has structure (Nobel Prize) electrical and magnetic distributions • Resonance Excitations  internal structure, rich spectroscopy (new particle search) constituent quark models • Deep Inelastic Scattering  70s: established quark-parton picture (Nobel Prize) parton distribution functions (PDFs) polarized PDFs : spin Structure TMDs, GPDs: 3-d structure: Factorization: observable Robert Hofstadter, Nobel Prize 1961 J.T. Friedman R. Taylor H.W. Kendall Nobel Prize 1990

  6. F2= 2xF1g2= 0

  7. Nucleon Structure Function: Deep-Inelastic Scattering • Bjorken Scaling and Scaling Violation • Gluon radiation – QCD evolution • One of the best experimental tests of QCD

  8. Polarized Structure Function/Distributions

  9. QCD and Nucleon Structure Study • Dynamical Chiral Symmetry Breaking <-> Confinement • Responsible for ~98% of the nucleon mass • Higgs mechanism is (almost) irrelevant to light quarks • Rapid development in theory • Lattice QCD • Dyson-Schwinger • Ads/CFT: Holographic QCD • …… • Direct comparisons limited to • Moments • Tensor charge • … • Direct comparison becomes possible • Experimental data with predictions from theory C.D. Roberts, Prog. Part. Nucl. Phys. 61 (2008) 50 M. Bhagwat & P.C. Tandy, AIP Conf.Proc. 842 (2006) 225-227 Mass from nothing!

  10. Imaging dynamical chiral symmetry breaking: pion wave function on the light front, Lei Chang, et al., arXiv:1301.0324 [nucl-th], Phys. Rev. Lett. 110 (2013) 132001 (2013) [5 pages]. Dyson-Schwinger Pion’s valence-quark Distribution Amplitude C.D. Roberts, Prog. Part. Nucl. Phys. 61 (2008) 50 Dilation of pion’s wave function is measurable in pion’s electromagnetic form factor at JLab12 A-rated:E12-06-10 • Established an one-to-one connection between DCSB and the pointwise form of the pion’s wave function. • Dilation measures the rate at which dressed-quark approaches the asymptotic bare-parton limit • Experiments at JLab12 can empirically verify the behaviour of M(p), and hence chart the IR limit of QCD Craig Roberts: Mapping Parton Structure and Correlations (62p)

  11. Lattice QCD A new proposal • Using the Infinite Momentum Frame formalism. • Start with static correlation in the z-direction. X. Ji, to be published First exploratory study by Huey-Wen Lin presented at the QCD Evolution Workshop at JLab, May 2013.

  12. The extension of the approach • GPDs • TMDs

  13. Single Spin Asymmetries with A Transversely Polarized 3He (n) JLab Hall A E06-010 Exploratory Measurements

  14. Unified View of Nucleon Structure d2kT drz d3r TMD PDFs f1u(x,kT), .. h1u(x,kT)‏ GPDs/IPDs 6D Dist. Wpu(x,kT,r ) Wigner distributions (X. Ji ) 3D imaging dx & Fourier Transformation d2kT d2rT Form Factors GE(Q2), GM(Q2)‏ PDFs f1u(x), .. h1u(x)‏ 1D

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

  16. BNL FNAL lepton lepton proton lepton JPARC pion proton antilepton Drell-Yan electron pion positron pion e–e+ to pions Access TMDs through Hard Processes EIC proton SIDIS • Gauge invariant definition (Belitsky,Ji,Yuan 2003) • Universality of kT-dependent PDFs (Collins,Metz 2003) • Factorization for small kT. (Ji,Ma,Yuan 2005)

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

  18. COMPASS Sivers asymmetry 2010 data x > 0.032 region - comparison with HERMES results NEW NEW

  19. Status of Transverse Spin/Structure Study Large single spin asymmetry in pp->pX (Fermi, RHIC-spin) Collins Asymmetries - sizable for the proton (HERMES and COMPASS) large at high x,p- and p+has opposite sign unfavored Collins fragmentation as large as favored (opposite sign)? Sivers Asymmetries - non-zero for p+ from proton (HERMES), new COMPASS data - large for K+? - sign mismatch? Collins Fragmentation from Belle Global Fits/models: Anselminoet al., Yuan et al., Pasquiniet al., Ma et al., … TMD evolution, a lot of progress in the last couple years Very active theoretical and experimental efforts JLab (6 GeV and 12 GeV), RHIC-spin, Belle, FAIR, J-PARC, EIC, … First neutron measurement from Hall A 6 GeV (E06-010) SoLID with polarized p and n(3He) at JLab 12 GeV Unprecedented precision with high luminosity and large acceptance

  20. E06‑010 ExperimentSpokespersons: Chen/Evaristo/Gao/Jiang/Peng Luminosity Monitor • First measurement on n (3He) • Polarized 3He Target • Polarized Electron Beam, 5.9 GeV • 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 TOF, RICH, Aerogel Cherenkov • 7 PhD Thesis Students (All graduated) + new students (Yuxian Zhao, ...) Beam Polarimetry (Møller + Compton)

  21. Performance of 3He Target • High luminosity: L(n) = 1036 cm-2 s-1 • Record high 50-65% polarization in beam with automatic spin flip / 20min • <P> = 55.4% ± 0.4% (stat. per spin state) ± 2.7 % (sys.) ~90% ~1.5% ~8%

  22. Published Results (I) from JLab Hall A E06-010 with a Transversely Polarized 3He (n) • Collins/Sivers Asymmetries on p+/p- • Worm-Gear: Trans-helicity on p+/p- X. Qian at al., PRL 107:072003(2011) J. Huang et al., PRL. 108, 052001 (2012).

  23. Neutron Results with Polarized 3He from JLab X. Qian PRL 107 072003 (2011) • Sizable Collins π+ asymmetries at x=0.34? • Sign of violation of Soffer’s inequality? • Data are limited by stat. Needs more precise data! • Negative Sivers π+ Asymmetry • Consistent with HERMES/COMPASS • Independent demonstration of negative d quark Sivers function. Blue band: model (fitting) uncertainties Red band: other systematic uncertainties

  24. Neutron ALT and Trans-Helicity g1T • Access • Dominated by real part ofinterference between L=0 (S) and L=1 (P) states • Imaginary part -> Sivers effect • No GPD correspondence • Measured by COMPASS and HERMES on p and D targets Huang, et. al. PRL. 108, 052001 (2012) • E06-010 - First data on effectively neutron target • Consistent with models in signs • Suggest larger asymmetry, possible interpretations: • Larger quark spin-orbital interference • different PT dependence • larger subleading-twist effects g1T=

  25. Preliminary New Results (I) from JLab Hall A E06-010 with a Transversely Polarized 3He (n) Collins/Sivers Asymmetries on K+/K- Analysis by Y. Zhao (USTC), Y. Wang (UIUC) Pretzelosity Asymmetries for p+/p- Analysis by Y. Zhang (Lanzhou), X. Qian (Caltech)

  26. Kaon PID by Coincidence time of flightCross checked with RICH results K+/π+ ratio: ~5%K-/π- ratio: ~1%

  27. Preliminary K+/K- Collins and SiversAsymmetries on 3He

  28. PretzelosityResults on Neutron PretzelosityAsymmetries, For both p+ and p-, consistent with zero within uncertainties. Preliminary Results HERMES

  29. Preliminary New Results (II)from JLab Hall A Inclusive Electron SSA a Polarized 3He (n) • DIS Analysis by J. Katech(W&M), X. Qian (Caltech) • Quasi-elastic by Y. Zhang (Rutgers), B. Zhao (W&M)

  30. Inclusive Target Single Spin Asymmetry θ 3He e- • Unpolarizede- beam incident on 3He target polarized normal to the • electron scattering plane. • However, Ay=0 at Born level, •  sensitive to physics at order α2; two-photon exchange. • In DIS case: related to integral of Sivers • (Q)Elastic: Calculable at large Q2 using moments of GPD’s • Measurement of Ay at large Q2 provides access to GPD’s

  31. Inclusive Target SSA: DIS neutron SSA from 3He(e,e’) Vertically polarized target HERMES proton data Measured average: Ay = 0.94 ± 0.32 x 10-2 A. Airapetian et al, Phys. Lett. B682, 351 (2010)

  32. Preliminary QE 3He and neutron SSA results 3He(e,e’) Ay3He neutron GPD calculation -- Q2dependence in the quasi-elastic SSA, Ay -- Agrees with GPD model** at Q2 = 1.0 GeV2. -- TPEX important , -relevant for GEp/GMp ?

  33. Preliminary New Results (IV) from JLab Hall A E06-010 with a transversely polarized 3He (n) Inclusive Hadron SSA • Analysis by K, Allada (JLab), Y. Zhao (USTC)

  34. Inclusive Hadron Electroproduction e + N↑h + X (h = p, K, p) pT • Why a non-zero AN isinteresting? • Analogues to AN in collision • Simpler than due to only one quark channel • Same transverse spin effects as SIDIS and p-p collisions (Sivers, Collins, twist-3) • Clean test TMD formalism (at large pT~ 1 GeV or more) • To help understand mechanism behind large AN in in the TMD framework

  35. Transverse SSA in Inclusive Hadron Preliminary p- p+ • Target spin flip every 20 minutes • Acceptance effects cancels • Overall systematic check with AN at ϕS= 0 • False asymmetry < 0.1% False Asymmetry

  36. E06-010: Inclusive Hadron SSA (AN) • Clear non-zero target SSA • Opposite sign forp+andp- Preliminary

  37. E06-010: Inclusive Hadron SSA (AN) • Clear non-zero target SSA • Opposite sign forp+andp- • AN at low pT not very well • understood Preliminary Preliminary

  38. Future: TMD study with SoLID at 12 GeVJLab Hall A Precision 4-D mapping of Collins/Sivers/Pretzelosity/Worm-Gear I/II with Polarized 3He (Neutron) and Proton Di-Hadron Production

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

  40. H1, ZEUS Kinematics Coverage of the 12 GeV Upgrade H1, ZEUS 27 GeV 11 GeV 11 GeV 200 GeV JLab Upgrade JLab @ 12 GeV COMPASS W = 2 GeV HERMES The 12 GeV Upgrade is well matched to studies in the valence quark regime. 0.7

  41. 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

  42. Physics Program for SoLID • SoLID: large acceptance, capable of handling high luminosity • (up to~1039 with baffle, up to ~1037 without baffle) • Ideal for precision Inclusive-DIS (PVDIS) and SIDIS experiments • Excellent for selected exclusive reactions (ex. J/Y) • Five high impact experiments approved (4 with “A” rating, 1 A- rating): • SIDIS: E12-10-006 (3He-T), E12-11-007 (3He-L), E12-11-108 (proton-T) • PVDIS: E12-10-007 (deuteron and proton) • J/y: E12-12-006

  43. SoLID Collaborators from China

  44. Nucleon Structure (TMDs) with SoLID • Semi-inclusive Deep Inelastic Scattering program: • Large Acceptance + High Luminosity • + Polarized targets 4-D mapping of asymmetries Tensor charge, TMDs … • Lattice QCD, QCD Dynamics, Models. Solenoidal Large Intensity Device (SoLID) • International collaboration (8 countries, • 50+ institutes and 190+ collaborators) • Rapid Growth in US‐China Collaboration • Chinese Hadron collaboration • (USTC, CIAE, PKU, Tsinghua U, Lanzhou, IMP,+) • - large GEM trackers • - MRPC-TOF • 3 A rated SIDIS experiments approved for SoLID • with 2 having Chinese collaborators as • co-spokesperson (Li from CIAE and Yan from USTC)

  45. Mapping of Collins/Siver 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- • Precision Map in region • x(0.05-0.65) z(0.3-0.7) • Q2(1-8) • PT(0-1.6) • <10% u/d quark tensor charge

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

  47. Expected Improvement: Sivers Function f1T= • Significant Improvement in the valence quark (high-x) region • Illustrated in a model fit (from A. Prokudin)

  48. E12-11-107: Worm-gear functions (“A’ rating: ) Spokespersons: J. P. Chen/J. Huang/Y. Qiang/ W. Yan h1L⊥(1) • 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. P-D int. h1L= S-P int. Center of points: g1T=

  49. Precision dihadron (p+/p-) production on a transversely polarized 3He (n) • Extract transversity on neutron • Provide crucial inputs for flavor separation of transversity talk by M.Radici Measure Transversity via Dihadron with SoLIDLoIsubmitted to Jlab PAC 40, J. Zhang, J. P. Chen, A. Courtoy, H. Gao Wide xb and Q2 coverages Projected Statistics error for one (Mpp,zpp) bin, integrated over all y and Q2.

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