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Harut Avakian (JLab)

SIDIS measurements of transverse and longitudinal spin azimuthal asymmetries related to higher twist PDFs. Harut Avakian (JLab). Transversity 2011, Aug 29, 2011. Outline. Higher twists in SIDIS quark-gluon correlations experimental results model calculations and lattice simulations

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Harut Avakian (JLab)

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  1. SIDIS measurements of transverse and longitudinal spin azimuthal asymmetries related to higher twist PDFs Harut Avakian (JLab) Transversity 2011, Aug 29, 2011 H. Avakian, Transversity 2011

  2. Outline Higher twists in SIDIS quark-gluon correlations experimental results model calculations and lattice simulations Future measurements measuring higher twist distributions in di-hadron production extraction of HT functions from azimuthal asymmetries Physics background to leading observables Summary Quark-gluon correlations (like kT-effects ) lead to azimuthal modulations in hadron production in hard scattering processes. H. Avakian, Transversity 2011

  3. SIDIS kinematical plane kT p┴ PT = p┴+zkT H. Avakian, INT, Nov 9

  4. Azimuthal distributions in SIDIS h.t. T h.t. h.t. EMC (1987) Large cosf modulations observed by EMC were reproduced in electroproduction of hadrons in SIDIS with unpolarized targets at COMPASS and HERMES H. Avakian, Transversity 2011

  5. Measurements of SS azimuthal asymmetries in SIDIS HERMES (2000) CLAS preliminary COMPASS 0.18<x<0.24 p+ p- p0 Large sinf modulations have been observed in electroproduction of hadrons in SIDIS with longitudinally polarized targets H. Avakian, Transversity 2011

  6. Beam SSA: ALU Jlab/HERMES/COMPASS HERMES CLAS W. Gohn(DIS2011) CLAS C.Schill(DIS2011) HT SSAs are comparable at JLab, HERMES and COMPASS 6 H. Avakian, Transversity 2011

  7. SSA at large xF CLAS COMPASS 0 moves to lower xF with energy? ANL s=4.9 GeV ANL s=4.9 GeV BNL s=6.6 GeV BNL s=6.6 GeV RHIC s=62.4 GeV RHIC s=62.4 GeV FNAL s=19.4 GeV FNAL s=19.4 GeV H. Avakian, Transversity 2011

  8. More polarized target HT SSAs Transversely polarized Longitudinally polarized How transversely polarized quarks were generated? Sivers type Collins type H. Avakian, Transversity 2011

  9. Contributions in large sinusoidal modulations observed in experiments from Collins fragmentation fh y PT fS=p x What makes them transversely polarized in the lepton plane? Collins Effect: azimuthal modulation of the fragmentation function FUT∞h1H1┴ sT(q×PT)↔H1┴ y PT fC sT fC fh D(z,PT)=D1(z,PT)+H1┴(z,PT)sin(fh- fS’) hadronizing quark pol. fS’ x fC sin(2fh) H. Avakian, Transversity 2011 Collinear twist-3 PDFs

  10. Transverse force on the polarized quarks Quark polarized in the x-direction with kT in the y-direction Force on the active quark right after scattering (t=0) Interpreting HT (quark-gluon-quark correlations) as force on the quarks (Burkardt hep-ph:0810.3589) 10 H. Avakian, Transversity 2011

  11. Beam SSA: ALU from CLAS @ JLab Photon Sivers Effect Afanasev & Carlson, Metz & Schlegel, Gamberg et al. Beam SSA from initial distribution(Boer-Mulders TMD) F.Yuan using h1┴ from MIT bag model 0.5<z<0.8 Beam SSA from hadronization (Collins effect) by Schweitzer et al. 11 H. Avakian, Transversity 2011

  12. H.A.,A.Efremov,P.Schweitzer,F.Yuan arXiv:1001.5467 Model predictions for higher twists “interaction dependent” Models agree on a large HT distributions H. Avakian, Transversity 2011

  13. Lattice calculations of HT distributions (PDFs in terms of Lorenz invariant amplitudes Musch et al, arXiv:1011.1213) Lattice provides important complementary information on FT for all HT distributions H. Avakian, Transversity 2011

  14. Lattice calculations of HT distributions Lattice provides important cross check with data and models for all HT TMDs (Musch et al, arXiv:1011.1213) Lattice results for u-d can be directly compared to models and data. H. Avakian, Transversity 2011

  15. Current Fragmentation h Twist-2 Twist-3 A. Bacchetta et al. hep-ph/0611265 • Several unknown distribution and fragmentation functions involved, making extraction model dependent • Factorization of higher twists in kT-dependent SIDIS not proved H. Avakian, Transversity 2011

  16. BGMP: extraction of kT-dependent PDFs Need: project x-section onto Fourier mods in bT-space to avoid convolution Boer, Gamberg, Musch &Prokudin arXiv:1107.5294 generated acceptance 0.3<x<0.36 0.5<z<0.6 Bessel weighting • provides a model independent way to study kinematical dependences of TMD • requires wide range in hadron PT H. Avakian, Transversity 2011

  17. h1 h2 Dihadron Fragmentation - fractions of energy carried by a hadrons • Factorization proven • Evolution known • Extracted at BELLE for pp pairs, • planned for pK pairs Dihadron productions offers exciting possibility to access HT effects H. Avakian, Transversity 2011

  18. Dihadron Fragmentation • Significant DiFF published by BELLE • Evolution effects small for DiFF/D1 • DiFF represent the easiest way to measure the polarization of a fragmenting quark • DiFF contain information on interferences between different channels H. Avakian, Transversity 2011

  19. Dihadron Fragmentation Dihadron production cross section in case of one photon exchange +.. H. Avakian, Transversity 2011

  20. SSA in Dihadron production Difference of asymmetries measured with unpolarized and longitudinally polarized targets depends only on the DiFF and HT functions H. Avakian, Transversity 2011

  21. Dihadron beam SSA with CLAS6 CLAS-e1dvcs CLAS-e1f p+p- p0p+ preliminary preliminary Significant dihadron asymmetries measured at 6 GeV by CLAS H. Avakian, Transversity 2011

  22. p p p K p p Dihadron production with CLAS12 Use the clasDIS (LUND based) generator + FASTMC to study ppandpK pairs xF- momentum in the CM frame CFR-CFR TFR Dihadron sample defined by SIDIS cuts+xF>0 (CFR) for both hadrons H. Avakian, Transversity 2011

  23. Dihadron production with CLAS12 spectator model cQSM JLab PR12-11-109: 54 days of unpolarized proton and deuteron running will allow precision measurement of HT distribution e bag model H. Avakian, Transversity 2011

  24. “flavor blind” HT effects as background: Boer-Mulders distribution Pasquini&Yuan(2010) Gamberg et al (2008) Sun et al (2008) Background contributions : Higher twist azimuthal moments kinematical HT (Cahn) dynamical HT (Berger-Brodsky) Radiative correction Acceptance Wide range in Q2 and PT accessible with CLAS12 are important for cos2f studies (all background contributions are HT) H. Avakian, Transversity 2011

  25. Azimuthal moments of A1 and flavor decomposition EIC Acceptance in f (and PT) may affect the A1 and flavor decomposition ( in particular Ds extractions) in SIDIS? 25 H. Avakian, Transversity 2011

  26. Summary • Latest experimental data indicate that quark-gluon/quark correlations leading to spin and azimuthal asymmetries may be very significant • Measurements of HT are consistent in sign and magnitude for SIDIS experiments at very different energies • Higher Twist distributions are accessible in single and double spin azimuthal asymmetries, can be calculated in models and lattice • Di-hadron production provide exciting possibility to measure HT functions in model independent way within collinear factorization • Higher twists are indispensable part of SIDIS analysis and their understanding is crucial for interpretation of SIDIS leading twist observables H. Avakian, Transversity 2011

  27. Support slides…. H. Avakian, Transversity 2011

  28. FAST-MC for CLAS12 SIDIS MC in 8D (x,y,z,f,fS,pT,l,p) Simple model with 10% difference between f1 (0.2GeV2) and g1 widths with a fixed width for D1 (0.14GeV2) CLAS12 acceptance & resolutions p┴ Events in CLAS12 PT = p┴+zkT Lund-MC Reasonable agreement of kinematic distributions with realistic LUND simulation H. Avakian, Transversity 2011

  29. Anselmino/Barone/Kotzinian arXiv:1107.2292 (2011) h1 h2 Fracture Function: conditional probabilities to find a quark with certain polarization and longitudinal momentum fraction xB and transverse momentum kT inside a nucleon fragmenting into a hadron carrying a fraction z of the nucleon longitudinal momentum and a transverse momentum PT h1 h2 Hadronization in current and target regions H. Avakian, Transversity 2011

  30. HT effects with transverse target H. Avakian, Transversity 2011

  31. Higher Twist SSAs Target sinf SSA (Bacchetta et al. 0405154) Discussed as main sources of SSA due to the Collins fragmentation In jet SIDIS only contributions ~ D1 survive The same unknown fragmentation function Beam sinf SSA With H1┴ (p0)≈0(or measured) Target and Beam SSA can be a valuable source of info on HT T-odd distribution functions H. Avakian, Transversity 2011

  32. Dihadron simulations with LUND-MC @6 GeV H. Avakian, Transversity 2011

  33. Azimuthal moments with unpolarized target quark polarization 33 H. Avakian, Transversity 2011 JLab, Nov 25

  34. Azimuthal moments with unpolarized target quark polarization 34 H. Avakian, Transversity 2011 JLab, Nov 25

  35. SSA with unpolarized target quark polarization 35 H. Avakian, Transversity 2011 JLab, Nov 25

  36. Measurements of SS azimuthal asymmetries in SIDIS Large cosf and sinf modulations have been observed in electroproduction of hadrons in SIDIS with polarized and unpolarized targets HERMES (2000) CLAS (2003) EMC (1987) Related to spin-orbit correlations in fragmentation? H. Avakian, Transversity 2011

  37. SSA with unpolarized target quark polarization 37 H. Avakian, Transversity 2011 JLab, Nov 25

  38. SSA with long. polarized target quark polarization H. Avakian, Transversity 2011

  39. SSA with long. polarized target quark polarization H. Avakian, Transversity 2011

  40. SSA with unpolarized target quark polarization H. Avakian, Transversity 2011

  41. SSA with unpolarized target quark polarization H. Avakian, Transversity 2011

  42. SSA with transversely polarized target quark polarization H. Avakian, Transversity 2011

  43. Twist-3 PDFs : “new testament” H. Avakian, Transversity 2011

  44. H. Avakian, Transversity 2011

  45. Studies of Dihadron Electroproduction in DIS with Unpolarized and Longitudinally Polarized Hydrogen and Deuterium Targets Harut Avakian (JLab) JLab PAC38, Aug 24, 2011 • Proposal PR12-11-109 • Measure hadron pairs in current and target fragmentation regions • Study higher-twist distribution functions and interference effects in hadronization Spokespersons: S. Anefalos-Pereira (LNF-INFN) , H. Avakian (JLab), A. Courtoy (U. Pavia) K. Griffioen (W&M), L. Pappalardo (INFN-Ferrara) H. Avakian, Transversity 2011

  46. Model predictions: polarized target • Models agree on a large target SSA for pppair production • Deuteron target measurements provide complementary information on flavor dependence H. Avakian, Transversity 2011

  47. The azimuthal terms at low Pt • No significant difference between the results for π- or π+ , or H and D. • At low Pt the azimuthal dependence is consistent with zero. σSIDIS=σDIS·∑ei2[qi(x,Q2)Di(z)]·be-bpT2{1+Acos(φ)+Bcos(2φ)} A and B are the weights of the azimuthal terms (σLT and σTT) • Solid lines are Cahan theoretical predictions • A ~ (Pt/Q)·ξ • B ~ (Pt2/Q2)·ξ2 • Where ξ= z2/(1+z2) • At <Pt> ~0.05 GeV • A ~ B ~ 0 for SIDIS A and B are much larger in exclusive pion production (open symbols) H. Avakian, Transversity 2011

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