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Transverse spin physics at CLAS and CLAS12

Transverse spin physics at CLAS and CLAS12. H.Avakian (JLab). BARYONS’10  Dec. 7-11, 2010, Osaka, Japan. Outline. Physics motivation k T -effects with unpolarized and longitudinally polarized target data Physics with transversely polarized hadrons and quarks

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Transverse spin physics at CLAS and CLAS12

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  1. Transverse spin physics at CLAS and CLAS12 H.Avakian (JLab) BARYONS’10  Dec. 7-11, 2010, Osaka, Japan H. Avakian, Baryons, Dec 10

  2. Outline Physics motivation kT-effects with unpolarized and longitudinally polarized target data Physics with transversely polarized hadrons and quarks Future studies of 3D PDFs at CLAS at 6 GeV Transverse structure & CLAS12 How spin-orbit correlations are related to the orbital momentum, longitudinal structure and nuclear effects? H. Avakian, Baryons, Dec 10

  3. Structure of the Nucleon Wpu(k,rT) “Mother” distributions (Wigner, GTMDs,..) d2rT d2kT TMD PDFs q(x,kT), Dq(x,kT)… GPD/IPDs H(x,rT), H~(x,rT)… Spin and longitudinal momentum correlations with kT and rT lead to observable effects in exclusive and semi-inclusive processes d2kT d2rT PDFsq(x), Dq(x)… 3 H. Avakian, Baryons, Dec 10

  4. Nucleon TMDs Transverse Momentum Distributions (TMDs) of partons describe the distribution of quarks and gluons in a nucleon with respect to x and the intrinsic transverse momentum kT carried by the quarks

  5. SIDIS: partonic cross sections kT p┴ PT = p┴+zkT Ji,Ma,Yuan Phys.Rev.D71:034005,2005 Use azimuthal moments in SIDIS to study spin-orbit correlations. 5 H. Avakian, Baryons, Dec 10

  6. 4K 1 K 0.6 K 0.05 K CLAS configurations ep→e’pX Inner Calorimeter HD-Ice e p- p+ Unpolarized and longitudinally polarized targets Unpolarized, longitudinally and transversely polarized targets • Polarized NH3/ND3 (no IC, ~5 days) • Unpolarized H (with IC ~ 60 days) • Polarized NH3/ND3 with IC 60 days • 10% of data on carbon • Polarized HD-Ice (no IC, 25 days) • Polarizations: • Beam: ~80% • NH3 proton 80%,ND3 ~30% • HD (H-75%,D-25%) 6 H. Avakian, Baryons, Dec 10

  7. 2 SIDIS with JLab at 6 GeV Scattering of 5.7 GeV electrons off polarized proton and deuteron targets • DIS kinematics, Q2>1 GeV2, W2>4 GeV2, y<0.85 • 0.4>z>0.7, MX2>2 GeV2 epX Large PT range and full coverage in azimuthal angle f crucial for studies 7 H. Avakian, Baryons, Dec 10

  8. A1 PT-dependence in SIDIS arXiv:1003.4549 0.4<z<0.7 M.Anselmino et al hep-ph/0608048 m02=0.25GeV2 mD2=0.2GeV2 p+ A1 suggests broader kT distributions for f1 than for g1 p- A1 may require non-Gaussian kT-dependence for different helicities and/or flavors H. Avakian, Baryons, Dec 10

  9. Quark distributions at large kT: lattice B.Musch et al arXiv:1011.1213 Higher probability to find a quark anti-aligned with proton spin at large kT and bT B.Pasquini et al Significant correlations of spin and transverse degrees of freedom predicted 9 H. Avakian, Baryons, Dec 10

  10. Quark distributions at large kT: lattice q Dq JMR model MR, R=s,a B.Musch et al arXiv:1011.1213 Du/u Sign change of Du/u consistent between lattice and diquark model 10 H. Avakian, Baryons, Dec 10

  11. Lattice Anselmino Collins A1 PT-dependence arXiv:1003.4549 A1 PT PT CLAS data suggests that width of g1 is less than the width of f1 New CLAS data would allow multidimensional binning to study kT-dependence for fixed x H. Avakian, Baryons, Dec 10

  12. Longitudinal Target SSA measurements at CLAS ~10% of E05-113 data CLAS-2009 (E05-113) CLAS PRELIMINARY ep→e’pX p1sinf+p2sin2f CLAS-2000 W2>4 GeV2 p1= 0.059±0.010 p2=-0.041±0.010 p1=-0.042±0.015 p2=-0.052±0.016 p1=0.082±0.018 p2=0.012±0.019 Q2>1.1 GeV2 y<0.85 MX>1.4 GeV PT<1 GeV 0.12<x<0.48 0.4<z<0.7 Data consistent with negative sin2f for p+ 12 12 H. Avakian, Baryons, Dec 10

  13. B.Musch arXiv:0907.2381 B.Pasquini et al, arXiv:0910.1677 Kotzinian-Mulders Asymmetries HERMES CLAS (5 days) Worm gear TMDs are unique (no analog in GPDs) H. Avakian, Baryons, Dec 10

  14. Photon Sivers Effect Afanasev & Carlson, Metz & Schlegel Beam SSA from initial distribution(Boer-Mulders TMD) F.Yuan using h1┴ from MIT bag model Beam SSA: ALU from CLAS @ JLab 0.5<z<0.8 Beam SSA from hadronization (Collins effect) by Schweitzer et al. No leading twist contributions: provides access to quark-gluon correlations H. Avakian, Baryons, Dec 10

  15. Compare single hadron and dihadron SSAs fh y Only 2 terms with common unknown HT G~ term! PT fS=p x Chiral odd HT-distribution How can we separate the HT contributions? HT function related to force on the quark. M.Burkardt (2008) M.Radici H. Avakian, Baryons, Dec 10

  16. CLAS transversely polarized HD-Ice target HD-Ice target vs std nuclear targets • Small field (∫Bdl~0.005-0.05Tm) • Small dilution (fraction of events from polarized material) • Less radiation length • Less nuclear background (no nuclear attenuation) • Wider acceptance 16 H. Avakian, Baryons, Dec 10

  17. Collins SSAs CLAS E08-015 (2011) Anselmino et al CLAS with a transversely polarized target will allow measurements of transverse spin distributions and constrain Collins fragmentation function 17 H. Avakian, Baryons, Dec 10

  18. Measurement of Sivers function and GPD-E CLAS E08-015 (DVCS) (SIDIS) GPD-E=0 DVCS Transverse asymmetry (function of momentum transfer to proton) is large and has strong sensitivity to GPD-E CLAS will provide a measurements of Sivers asymmetry at large x, where the effect is large and models unconstrained by previous measurements. Meissner, Metz & Goeke (2007) 18 H. Avakian, Baryons, Dec 10

  19. LTCC DC R1, R2, R3 PCAL Solenoid 5T EC HTCC FTOF CLAS12 LTCC PCAL CLAS12 Lumi = 1035cm-2s-1 High beam polarization 80% High target polarization 85% NH3 (30 days) ND3 (50 days) Primary goal of experiments: EC HTCC FTOF study of the 3D structure of the nucleon L = 1035 cm-2s-1 Wide detector and physics acceptance allow studies of both current and target fragmentation regions using semi inclusive and exclusive processes H. Avakian, Baryons, Dec 10

  20. CLAS12: Kinematical coverage epX SIDIS kinematics Q2>1GeV2 W2>4 GeV2(10) y<0.85 MX>2GeV Large PT , Q2 accessible with CLAS12 are important for studies of the 3D structure and separation of HT contributions. H. Avakian, Baryons, Dec 10

  21. E12-06-112:Pion SIDIS E12-09-008: KaonSIDIS U E12-07-107:Pion SIDIS E12-09-009: KaonSIDIS L T LOI12-06-108: Pion SIDIS LOI12-09-004: KaonSIDIS q N TMDs program @ 12 GeV in Hall B PAC approved experiments & LoI • Complete program of TMDs studies for pions and kaons • Kaon measurements crucial for a better understanding of the TMDs “kaon puzzle” • Kaon SIDIS program requires an upgrade of the CLAS12 detector PID RICH detector to replace LTCC (talk by P. Rossi) Project under development H. Avakian, Baryons, Dec 10

  22. Longitudinally polarized target: helicity distributions High precision measurements of double spin asymmetries will significantly improve the knowledge of helicity distributions Wide range in PT of hadrons would allow measurements of transverse momentum dependence of partonic distributions in the valence region H. Avakian, Baryons, Dec 10

  23. Pretzelosity @ CLAS12: Exciting relation: (in bag & spectator model) helicity - transversity = ‘measure’ of relativistic effects • CLAS12 will provide pretzelosity measurement in the valence region for Kaons and pions. She, Zhu & Ma, Phys. Rev. D 79 (2009) In models (bag, diquark) pretzelosity defines the OAM B. Pasquini et al. arXiv:0806.2298 H. Avakian, Baryons, Dec 10

  24. PT-dependence of beam SSA ssinfLU(UL) ~FLU(UL)~ 1/Q (Twist-3) 1/PT 1/Q Perturbative region Nonperturbative TMD Check of the higher twist nature of observed SSA critical SSA test transition from non-perturbative to perturbative region H. Avakian, Baryons, Dec 10

  25. Summary • CLAS longitudinally polarized NH3 and ND3 target data provides superior sample of events allowing detailed studies of single and double spin asymmetries using multidimensional bins • Measurements of spin and azimuthal asymmetries with unpolarized, longitudinally polarized and transversely polarized targets in semi-inclusive processes at JLab : • Measure TMDs of partons in the valence region • Provide detailed info on partonic spin-orbit correlations • Study quark-gluon correlations (HT) • Study nuclear modification of 3D PDFs • CLAS12 will significantly increase the luminosity, kinematical coverage and particle identification capabilities of CLAS6 H. Avakian, Baryons, Dec 10

  26. Support slides…. H. Avakian, Baryons, Dec 10

  27. SIDIS with JLab at 6 GeV Some analysis topics for latest polarized proton and deuteron target data • Inclusive g1p • Inclusive g1d • DVCS AUL on proton • DVCS AULon neutron • DVCS ALL • SIDIS AUL & ALL for pions on proton • SIDIS AUL & ALL for pions on deuteron • SIDIS AUL & ALL for kaons and r+/-/0 on proton • Modifications of azimuthal moments in nuclei Large acceptance of CLAS allows simultaneous measurements of hard exclusive and semi-inclusive reactions providing complementary information on the complex nucleon structure. 27 H. Avakian, Baryons, Dec 10

  28. M.Osipenko H. Avakian, Baryons, Dec 10

  29. Some questions to address • What is the shape of kT-distributions? • Are there correlations between transverse space and momentum distributions? • Can kT-distributions be flavor dependent? • Are kT-distributions the same for different spin orientations? • How spin-orbit correlations change the momentum distributions? • What is the fraction of kT-generated in FSI? • How quark-gluon correlations affect transverse momentum and space distributions? • How nuclear medium changes kT and bT-distributions? • How gluons and sea are distributed in kT H. Avakian, Baryons, Dec 10

  30. Fits to unpolarized data Anselmino et al Collins et al Extracting widths from A1 Assuming the widths of f1/g1 x,z and flavor independent EMC H. Avakian, Baryons, Dec 10

  31. Nucleon TMDs Transverse Momentum Distributions (TMDs) of partons describe the distribution of quarks and gluons in a nucleon with respect to x and the intrinsic transverse momentum kT carried by the quarks

  32.   HDice • polarized targets of solid hydrogen, +HD (E06-101); e+HD (E08-021) • polarize to frozen-spin state at 12 mK, 15 tesla in new HDice Lab • transfer to CLAS In-Beam-Cryostat • renovated Lab in Test Lab Annex • installing polarizing equip • assembling Oxford dilution fridge - training SC magnet • new NMR electronics under test - optimize H  D spin transfer • fabricating CLAS target cells • HD purity analysis  prep time - chromatography & Raman scat HDice Lab Hall B H. Avakian, Baryons, Dec 10

  33. Single hadron production in hard scattering h TMD xF>0 (current fragmentation) h xF<0 (target fragmentation) xF- momentum in the CM frame Target fragmentation Current fragmentation semi-inclusive exclusive semi-exclusive h FF h DA DA h GPD M PDF 1 -1 xF 0 Fracture Functions kT-dependent PDFs Generalized PDFs Measurements in different kinematical regions for nucleon and nucleus provide complementary information on the complex nucleon structure. 33 33

  34. y PT fS= p/2+fh fS fh x fh y PT fS=p x Collins fragmentation & higher twists sT(q×PT)↔H1┴ D(z,PT)=D1(z,PT)+H1┴(z,PT)sin(fC) fC= fh- fS’ HT function related to force on the quark. M.Burkardt (2008) Interactions make difference fC sin(2fh) H. Avakian, Baryons, Dec 10

  35. 4K 1K 0.6K 0.05K   • designed for both  (Start Counter) and e- (mini-Torus) • ASME code review nearly complete • under construction HDice In-Beam Cryostat for CLAS HDice Transfer Cryostat HDice In-Beam Cryostat HDice IBC-CLAS loading H. Avakian, Baryons, Dec 10

  36. cosf moment in ALL-PT-dependence hep-ph/0608048 m02=0.25GeV2 mD2=0.2GeV2 CLAS PRELIMINARY PT-dependence of cosf moment of double spin asymmetry is most sensitive to kT-distributions of quarks with spin orientations along and opposite to the proton spin. 36 H. Avakian, Baryons, Dec 10

  37. e- p e-nr+ π+π0 Exclusive p+p- and p+p0 from CLAS e p e p π+ π- r+ • Measurements of ratios r+ /r0 , r+ /p+ … Ju,Jd Gluon exchange at low W suppressed (x-sections for r0 and r+ comparable) Quark exchange, which dominates, can be considered as part of SIDIS H. Avakian, Baryons, Dec 10

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