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Harut Avakian (JLab)

SIDIS results from JLAB. Harut Avakian (JLab). Mainz, April 1, 2009. Outline. Describe the complex nucleon structure in terms of partonic degrees of freedom of QCD. Physics motivation Transverse Momentum Distributions (TMDs) of quarks and spin-azimuthal asymmetries in semi-inclusive DIS

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Harut Avakian (JLab)

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  1. SIDIS results from JLAB Harut Avakian (JLab) Mainz, April 1, 2009 IWHSS09, Apr 1

  2. Outline Describe the complex nucleon structure in terms of partonic degrees of freedom of QCD • Physics motivation • Transverse Momentum Distributions (TMDs) of quarks and spin-azimuthal asymmetries in semi-inclusive DIS • SIDIS results from JLab at 6 GeV • Tests of the applicability of the partonic picture • Studies of spin-orbit correlations with CLAS • Measurements of TMDs at 6 GeV • Longitudinally polarized proton target measurements (E05-113) • Transversely polarized 3He (E06-010/011) and proton targets (E08-015) • Summary IWHSS09, Apr 1

  3. SIDIS kinematical plane and observables z U unpolarized L long.polarized T trans.polarized sin2f moment of the cross section for unpolarized beam and longitudinal target Transverse spin effects are observable as correlations of transverse spin and transverse momentum of quarks. IWHSS09, Apr 1

  4. Wpu(k,rT) “Mother” Wigner distributions d2kT d2rT GPDs/IPDs TMD PDFs f1u(x,kT), .. h1u(x,kT) d2kT Structure of the Nucleon quark polarization PDFs f1u(x), .. h1u(x) • Gauge invariant definition (Belitsky,Ji,Yuan 2003) • Universality of kT-dependent PDFs (Collins,Metz 2003) • Factorization for small kT. (Ji,Ma,Yuan 2005) IWHSS09, Apr 1

  5. CLAS at JLAB Electron beam energy 6 GeV Lumi ~1034cm-2sec-1 IWHSS09, Apr 1

  6. e p- p+ 2 SIDIS with CLAS at 6 GeV Scattering of 5.7 GeV electrons off unpolarized and polarized proton and deuteron targets • DIS kinematics, Q2>1 GeV2, W2>4 GeV2, y<0.85 • 0.4>z>0.7, MX2>2 GeV2 • Polarized NH3/ND3 (~5 days) • Polarized H 30+30 days (2001/2005) epX IWHSS09, Apr 1

  7. p multiplicities in SIDIS ep→e’pX M.Aghasyan Hall-C DSS (Q2=2.5GeV2) DSS (Q2=25GeV2) p+/- multiplicities at large z diverge from SIDIS predictions p0 multiplicities less affected by higher twists 0.4<z<0.7 kinematical range, where higher twists are expected to be small IWHSS09, Apr 1

  8. Tests of partonic picture with p+/p- ratios Hall-C @ 6 GeV Rpd+ Rpd- Both ratios agree with PDF models for z<0.7 (Mx>1.4 GeV) IWHSS09, Apr 1

  9. 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 IWHSS09, Apr 1

  10. Quark longitudinal polarization BBS/LSS no OAM q Dq Du/u JMR model MR, R=s,a (dipole formfactor), J.Ellis, D-S.Hwang, A.Kotzinian BBS/LSS with OAM Effect of the orbital motion on the q- may be significant (H.A.,S.Brodsky, A.Deur,F.Yuan 2007) For given xthesignof the polarization is changing at large kT IWHSS09, Apr 1

  11. A1 PT-dependence in SIDIS 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 IWHSS09, Apr 1

  12. 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 IWHSS09, Apr 1

  13. A1 PT-dependence Anselmino Collins CLAS data suggests that width of g1 is less than the width of f1 IWHSS09, Apr 1

  14. ST Intial quark polarization fS fS’ = p-fS sin(fh+fS) spin of quark flips wrt y-axis y PT fS= p/2+fh fS fh x y PT fS=fh fh x fh y PT fS=p x Collins Effect: azimuthal modulation of the fragmentation function FUT∞h1H1┴ sT(q×PT)↔H1┴ y fC PT fC sT D(z,PT)=D1(z,PT)+H1┴(z,PT)sin(fh- fS’) fh hadronizing quark fS’ x fC sin(2fh) IWHSS09, Apr 1

  15. TMD PDFs SIDIS (g*p->pX) x-section at leading twist • Measure Boer-Mulders distribution functions and probe the polarized fragmentation function • Measurements from different experiments consistent IWHSS09, Apr 1

  16. Kotzinian-Mulders asymmetry Transversely polarized quarks in the longitudinally polarized nucleon curves, cQSM from Efremov et al More data needed to clarify the situation with negative pions • Data indicate that spin-orbit correlations with long.pol. target may be significant • Provide measurement of SSA for all 3 pions, extract the RSMT TMD (Ralston-Soper (1979), Mulders-Tangerman (1995) 16 IWHSS09, Apr 1

  17. What comes next • Hall-A Transversely polarized 3He target measurement • (E06-010/011) Hall-B Longitudinally polarized proton (NH3) target measurement (E05-113) Hall-B Transversely polarized proton target measurement (E08-015) Calibrating Currently running September 2011 Fixed bins in x/Q2 Wide kinematical coverage , multiple hadronic states Correlations of transverse and longitudinal momenta (PT-dependences) in ALL Collins asymmetry with longitudinally polarized (proton) target Exclusive asymmetries as background Sivers asymmetry Collins asymmetry with transverse proton target Shape of proton studies Exclusive asymmetries as background Sivers asymmetry Collins asymmetry with transverse (neutron) target 17 IWHSS09, Apr 1

  18. Target Single-Spin Asymmetry in Semi-Inclusiven↑(e, e’p+/-) E06-010: Reaction on a Transversely Polarized 3He Target • First measurement of the neutron Collins and Sivers asymmetries in SIDIS. • High density polarized 3He target. • Run in Hall A from 10/24/08-2/5/09. 110 shift workers, 7 Ph.D. students. 16o g* BigBite 30o HRSL p pt ~ 65% (proposal 42%) e’ Polarized 3He Target e Cell: Maureen Cell: Astral IWHSS09, Apr 1

  19. Experimental Setup 50o 13o Polarized target (NH3/ND3) • Polarized NH3 with IC 60 days • Polarized HD-Ice (no IC, 25 days) IC Inner Calorimeter (424 PbWO4 crystals) to detect high energy photons at forward lab angles. IWHSS09, Apr 1

  20. ALL PT-dependence in SIDIS E05-113 M.Anselmino et al hep-ph/0608048 m02=0.25GeV2 mD2=0.2GeV2 0.4<z<0.7 • study the PT-dependence for different quark helicities and flavors for bins in x, m2 (x) • flavor decomposition in PT-bins. 20 IWHSS09, Apr 1

  21. Kotzinian-Mulders asymmetry E05-113 Transversely polarized quarks in the longitudinally polarized nucleon curves, cQSM from Efremov et al 60 days of CLAS L=1.5.1034cm-2s-1 • Provide measurement of SSA for all 3 pions, extract the RSMT TMD (Ralston-Soper (1979), Mulders-Tangerman (1995) • Study Collins fragmentation with longitudinally polarized target 21 IWHSS09, Apr 1

  22. CLAS transversely polarized HD-Ice target HD-Ice target vs std nuclear targets Heat extraction is accomplished with thin aluminum wires running through the target (can operate at T~500-750mK) • Pros • 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 • much better FOM, especially for deuteron • Cons • HD target is highly complex and there is a need for redundancy due to the very long polarizing times (months). • Need to demonstrate that the target can remain polarized for long periods with an electron beam with currents of order of 1-2 nA • Additional shielding of Moller electrons necessary (use minitorus) HD-Ice target at ~2nA ~ NH3 at 5 nA IWHSS09, Apr 1

  23. Collins SSAs CLAS E08-015 Anselmino et al (2007) Boffi et al (2009) helicity-transversity=pretzelosity CLAS with a transversely polarized target will allow measurements of transverse spin distributions and constrain Collins fragmentation function 23 IWHSS09, Apr 1

  24. 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) 24 IWHSS09, Apr 1

  25. Summary Significant azimuthal moments in pion production in SIDIS are measured using CLAS with longitudinally polarized target. Measurements of azimuthal dependences of double and single spin asymmetries indicate that correlations between spin and transverse motion of quarks may be significant. PT-dependences of the double and single-spin asymmetries provide important input for studies of flavor and helicity dependence of quark transverse momentum dependent distributions. Upcoming CLAS SIDIS experiments at 6 GeV will significantly improve the statistical precision of longitudinally polarized target data, and will provide new data on transversely polarized target IWHSS09, Apr 1

  26. Support slides…. IWHSS09, Apr 1

  27. IWHSS09, Apr 1

  28. Rpd-for any z, x! Factorization studies Simple LO picture in valence region: Rpd+for any z, pt (if d and u have same pt dependence)! IWHSS09, Apr 1

  29. TheCLASDetector ~ 200 physicists 37 institutions • large kinematical coverage • high luminosity • multi-particle final states • charged particles: • p>0.2 GeV/c • 8o<q<140o • sp/p~0.5% (q<30o) • sp/p~1-2%(q>30o) • sq=1mrad • sf=4mrad IWHSS09, Apr 1

  30. Sivers effect: proton CLAS E08-015 Vogelsang & Yuan Schweitzer et al • CLAS will provide a superior measurements of Sivers asymmetry at large x, where the effect is large and models unconstrained by previous measurements. • Measure also asymmetries in target fragmentation region and for exclusive r,r+,w,p,h channels (background) 30 IWHSS09, Apr 1

  31. Collins fragmentation: Longitudinally polarized target Kotzinian-Mulders Asymmetry proton deuteron Pasquini et al. • Study the Collins function of kaons • Provides independent information on the RSMT TMD IWHSS09, Apr 1

  32. ST fS fS fS’ = p-fS sin(fh+fS) spin of quark flips wrt y-axis FUU∞h1 ┴H1┴ sT(p×kT)↔ h1┴ ┴ (sTkT)(pSL)↔ h1L ┴ FUL∞h1L H1┴ Collins Effect: azimuthal modulation of the fragmentation function FUT∞h1H1┴ sT(q×PT)↔H1┴ y fC PT fC sT D(z,PT)=D1(z,PT)+H1┴(z,PT)sin(fh- fS’) fh fS’ x sin(fh+fS) y y PT fS= p/2+fh PT fS=fh fh fh cos(2fh) sin(2fh) fC x x sin(2fh) IWHSS09, Apr 1

  33. Hall A E06-010: Neutron (3He) Transversity • First JLab transverse SSA measurement: running now to 2/09 • First world neutron(3He) measurement Sivers: Orbital Angular Momentum Collins: transversity 33 IWHSS09, Apr 1 JLab, Nov 25

  34. Contributions to sin Double Polarized SIDIS TMDs Mulders et al IWHSS09, Apr 1

  35. Spin densities in transverse proton from Lattice G.Miller/”pretzelosity” (QCDSF/UKQCD) Boer-Mulders TMD u-quark Spin of quark d-quark IWHSS09, Apr 1

  36. SSA with unpolarized target quark polarization IWHSS09, Apr 1

  37. SSA with unpolarized target quark polarization IWHSS09, Apr 1

  38. SSA with long. polarized target quark polarization IWHSS09, Apr 1

  39. SSA with long. polarized target quark polarization IWHSS09, Apr 1

  40. CLAS: Fraction from baryonic decays in SIDIS Significant fraction from target fragmentation at pion momenta below 2 GeV IWHSS09, Apr 1

  41. 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 IWHSS09, Apr 1

  42. Brodsky & Yuan (2006) Collins Effect: from asymmetries to distributions need CLAS12 Combined analysis of Collins fragmentation asymmetries from SIDIS and e+e- (BELLE) would allow separation of transverse spin distributions (Anselmino et al., arXiv:0707.1197 ) IWHSS09, Apr 1

  43. BBS/LSS with OAM JLab@12GeV: Inclusive DIS BBS/LSS no OAM PDF measurements at large x provide additional information on OAM IWHSS09, Apr 1

  44. Azimuthal Asymmetries in SIDIS Chay,Ellis,Stirling-1991 Why <cosf> < 0 ? f=0 p x f=180 p Due to color coherence the configuration with gluon inside the quark cone is more probable IWHSS09, Apr 1

  45. Fragmentationp+ p+ p0 HT and Semi-Exclusive Pion Production E. Berger, S. Brodsky 1979 (DY), E.Berger 1980, A.Brandenburg, V. Khoze, D. Muller 1995 A.Afanasev, C.Carlson, C. Wahlquist Phys.Lett.B398:393-399,1997 • Azimuthal asymmetries with opposite sign from HT effects • Effect may be suppressed for semi-exclusive p0 compared to p+/- IWHSS09, Apr 1

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