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Studies of Spin-Orbit Correlations with CLAS

Studies of Spin-Orbit Correlations with CLAS. Harut Avakian (JLab). Deep PWG, Genova, Feb 27. Outline. Physics motivation spin-orbit correlations and widths of PDFs Spin asymmetries from eg1: A1 measurements for pions Extraction of g1 width from pi+ data Summary.

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Studies of Spin-Orbit Correlations with CLAS

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  1. Studies of Spin-Orbit Correlations with CLAS Harut Avakian (JLab) Deep PWG, Genova, Feb 27 H. Avakian, DPWG, Feb 27

  2. Outline Physics motivation spin-orbit correlations and widths of PDFs Spin asymmetries from eg1: A1 measurements for pions Extraction of g1 width from pi+ data Summary H. Avakian, DPWG, Feb 27

  3. Factorization of kT-dependent PDFs proven at low PT of hadrons (Ji et al) Twist-3 Transverse Momentum Dependent (TMD) Distributions Quark polarization • kT – leads to 3D description with 8PDFs Real and imaginary parts of the DL≠0 interference contributions Nucleon polarization H. Avakian, DPWG, Feb 27

  4. Polarized Semi-Inclusive DIS Cross section is a function of scale variables x,y,z U unpolarized L long.polarized T trans.polarized z H. Avakian, DPWG, Feb 27

  5. CLAS configurations with long.polarized target ep→e’pX Inner Calorimeter e p- p+ • Polarizations: • Beam: ~80% • NH3 proton 80% • Polarized NH3/ND3 (no IC, ~5 days) • Polarized NH3 with IC 60 days H. Avakian, DPWG, Feb 27

  6. Target fragmentation in SIDIS Use PEPSI MC to define the kinematic region where the partonic description works Pions from target fragments mainly at low energies, small z and PT H. Avakian, DPWG, Feb 27

  7. SSA with Longitudinal Target quark polarization Higher twist in fragmentation/or distribution In jet SIDIS only contributions ~ D1 survive With H1┴ (p0)≈0(or measured) Target (Beam) SSA can be a valuable source of info on HT T-odd distribution functions H. Avakian, DPWG, Feb 27

  8. Polarized target: HERMES vs CLAS at 5.7GeV ep → e’ p+ X ( Ee =5.7 GeV, MX > 1.1) x dependence of CLAS A1p (A┴=0) consistent with HERMES data Du/u from CLAS EG1 is consistent with GRV(GRVS) PDFs H. Avakian, DPWG, Feb 27

  9. A1-kinematic dependences inbending outbending Ratio to inclusive asymmetry will account the x-dependence H. Avakian, DPWG, Feb 27

  10. constituent quark model (Pasquini et al). A1 PT-dependence in SIDIS m02=0.25GeV2 mD2=0.2GeV2 M.Anselmino et al hep-ph/0608048 Como-2005 In perturbative limit predicted to be constant p+ ALL can be explained in terms of broader kT distributions for f1 compared to g1 H. Avakian, DPWG, Feb 27

  11. q Dq Du/u (dipole formfactor), J.Ellis, D-S.Hwang, A.Kotzinian Helicity distributions: Diquark model Jakob, Mulders, Rodrigues, Nucl. Phys. A 1997 JMR model MR, R=s,a For given xthesignof the polarization is changing at large kT Difference in q+=f1+g1 (quark aligned with proton spin) and q-=f1-g1 - (anti-aligned) kT-dependences may lead to observable effects H. Avakian, DPWG, Feb 27

  12. A1 PT-dependence in SIDIS 0.4<z<0.7 M.Anselmino et al hep-ph/0608048 m02=0.25GeV2 mD2=0.2GeV2 more data in 2009! p+ A1 suggests broader kT distributions for f1 compared to g1 p- A1 may require non-Gaussian kT-dependence for different helicities and/or flavors H. Avakian, DPWG, Feb 27

  13. cosf moment in A1-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. H. Avakian, DPWG, Feb 27

  14. Fits to unpolarized data Anselmino et al Collins et al Extracting widths from ALL Assuming the widths of f1/g1 x,z and flavor independent H. Avakian, DPWG, Feb 27

  15. A1 PT-dependence Anselmino Collins CLAS data suggests that width of g1 is less than the width of f1 H. Avakian, DPWG, Feb 27

  16. Summary double spin asymmetries measured at CLAS are consistent with HERMES and fits to world data, assuming the factorized picture PT-dependence of the double spin asymmetry provides access to kT-widths of transverse momentum dependent distributions of quarks. CLAS data suggests that the kT-width of the momentum distribution is wider than the width of the helicity distribution The suggestions of the review committee have been applied and the analysis note has been prepared for the next round of review. H. Avakian, DPWG, Feb 27

  17. Support slides…. H. Avakian, DPWG, Feb 27

  18. 50o 13o Experimental Setup (CLAS EG1+IC) Polarized target (eg1) • solid NH3 polarized target • proton polarization ~80% • high lumi ~ 21034 s-1cm-2 IC Inner Calorimeter (424 PbWO4 crystals) for the detection of high energy photons at forward lab angles (e1-DVCS). H. Avakian, DPWG, Feb 27

  19. p quark Collinear Fragmentation The only fragmentation function at leading twist for pions in eN→e’pX is D1(z) Ee =5.7 GeV No significant variation observed in z distributions of p+ for different x ranges (0.4<z<0.7, MX>1.5) and for A1p as a function of PT H. Avakian, DPWG, Feb 27

  20. p0 multiplicities ep→e’p0X M.Aghasyan DSS (Q2=2.5GeV2) DSS (Q2=25GeV2) p0 multiplicities consistent with SIDIS predictions H. Avakian, DPWG, Feb 27

  21. sinf SSA analysis for pi0 Measure both for 3 pions and combine to separate different contributions. With H1┴ (p0)≈0(or measured) Target (Beam) SSA can be a valuable source of info on HT T-odd distribution functions H. Avakian, DPWG, Feb 27

  22. Dilution factor in SIDIS Fraction of events from polarized hydrogen in NH3 Nu,Np -total counts from NH3 and carbon normalized by lumi ru, rp -total areal thickness of hydrogen (in NH3), and carbon target Cn=Nitr/Carbon ratio (~0.98) Diff. symbols for diff x-bins p- Multiple scattering and attenuation in nuclear environment introduces additional PT-dependence for hadrons H. Avakian, DPWG, Feb 27

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