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H. Avakian , N. Kalantarians

CLAS & CLAS12 Measurements with Polarized Targets. H. Avakian , N. Kalantarians. Workshop on High Luminosity Polarized Targets for the 12GeV Era. JLab , June 18. Outline. Transverse structure of the nucleon and partonic correlations. Physics motivation

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H. Avakian , N. Kalantarians

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  1. CLAS & CLAS12 Measurements with Polarized Targets H. Avakian, N. Kalantarians Workshop on High Luminosity Polarized Targets for the 12GeV Era JLab, June 18 Jlab, June 18, 2010

  2. Outline Transverse structure of the nucleon and partonic correlations Physics motivation kT-effects with unpolarized and longitudinally polarized target data Double spin asymmetries Single Spin Asymmetries Physics with transversely polarized hadrons and quarks kT-effects and SSA in pion production correlations between transverse degrees of freedom Studies of 3D PDFs at CLAS at 6 GeV and beyond Summary Jlab, June 18, 2010

  3. Wpu(k,rT) “Mother” Wigner distributions d2rT Structure of the Nucleon d2kT TMD PDFs f1u(x,kT), .. h1u(x,kT) GPDs/IPDs H,E,…HT d2kT d2rT PDFs f1u(x), .. h1u(x) Analysis of SIDIS and DVMP are complementary Jlab, June 18, 2010

  4. kT-dependent PDFs and FFs: “new testament” No analog in twist-2 appear in sinf moment of ALU and AUL Baccetta, Diehl, Goeke, Metz, Mulders, Schlegel EPJ-2007 quark-gluon-quark correlations responsible for azimuthal moments in the cross section Jlab, June 18, 2010

  5. SIDIS: partonic cross sections kT p┴ PT = p┴+zkT Ji,Ma,Yuan Phys.Rev.D71:034005,2005 Is the info on x-kT correlations accessible in kT integrated observables? 5 5 Jlab, June 18, 2010

  6. 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 HT function related to force on the quark. M.Burkardt (2008) sin(2fh) Jlab, June 18, 2010

  7. Sivers mechanisms for SSA fS SIDIS Drell-Yan - M.Burkardt (2000) HT asymmetries (T-odd) PT FS Correlation between quark transverse momentum and the proton spin fkT Proton polarization x No leading twist, provide access to quark-gluon correlations 7 Jlab, June 18, 2010

  8. Quark distributions at large kT: lattice B.Musch arXiv:0907.2381 Analysis of same distributions using gaussian distributions in terms of f1&g1 and q+/q- yield different PDFs. 8 8 8 Jlab, June 18, 2010 H. Avakian, JLab, April 26 H. Avakian, JLab, May 3

  9. Quark distributions at large kT: lattice H. Mkrtchyan et al.Phys.Lett.B665:20-25,2008. B.Musch arXiv:0907.2381 Higher probability to find a d-quark at large kT 9 9 Jlab, June 18, 2010

  10. CLAS slightly lower, but may have bigger Anselmino et al from EMC data → = 0.25 Wider at smaller beam energies? Transverse momentum distributions of hadrons Gauss 10 Jlab, June 18, 2010 H. Avakian, JLab, May 3

  11. LTCC FTOF DC R1, R2, R3 Central Detector PCAL EC Solenoid 5T Forward Detector CTOF SVT HTCC TORUS CLAS12 Track resolution: dp (GeV/c) 0.003p + 0.001p2 dq (mr) < 1 df (mr) < 3 Wide detector and physics acceptance (current/target fragmentation) High beam polarization 85% High target polarization 85% Lumi > 1035cm-1s-1 Forward carriage Jlab, June 18, 2010

  12. CLAS Longitudinally Polarized Solid Target LHe transfer line He-4 Pump Out Needle Valves He-4 Pumping tube Heat shield Beam 10 cm Beam tube separator LHe fill tube Outer vacuum jacket 1 K heat exchanger wave guide • Horizontal DNP Polarized Target. • Field provided by warm bore solenoid. • Center of the target is at 2 m from the solenoid entrance, surrounded by SVT. • Beam along axis of refrigerator. • 4He Evaporation Refrigerator. • One target cell (no ladder). • UVa, ODU, CNU, JLab Jlab, June 18, 2010

  13. CLAS12: Kinematical coverage epX SIDIS kinematics Q2>1GeV2 W2>4 GeV2(10) y<0.85 MX>2GeV Large Q2 accessible with CLAS12 are important for separation of HT contributions Jlab, June 18, 2010

  14. Large sinf for all pions and no indication of sin2fforp0 s suggests Sivers dominance Longitudinal Target SSA measurements at CLAS (E05-113) • Complete azimuthal coverage crucial for separation of sinf, sin2f moments W2>4 GeV2 Q2>1.1 GeV2 y<0.85 0.4<z<0.7 MX>1.4 GeV PT<1 GeV 0.12<x<0.48 14 Jlab, June 18, 2010

  15. 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 • New experiment with 10 times more data will study the PT-dependence for different quark helicities and flavors for bins in x to check if m0< m2 15 Jlab, June 18, 2010

  16. 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 Jlab, June 18, 2010

  17. Multiple scattering and attenuation in nuclear environment introduces additional PT-dependence for hadrons p+ yield ratios to deuteron 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 HD-Ice target at ~2nA ~ NH3 at 5 Na (L~5.1033cm-2s-1) 17 Jlab, June 18, 2010

  18. Collins SSAs CLAS E08-015 (2011) H.A.,A.Efremov,P.Schweitzer,F.Yuan Anselmino et al helicity-transversity=pretzelosity CLAS with a transversely polarized target will allow measurements of transverse spin distributions and constrain Collins fragmentation function 18 Jlab, June 18, 2010

  19. 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) 19 Jlab, June 18, 2010

  20. Summary Measurements of azimuthal dependences of double and single spin asymmetries in SIDIS (TMDs) indicate that there are significant correlations between spin and transverse momentum distribution of quarks. Sizable higher twist asymmetries measured in SIDIS indicate the quark-gluon correlations may be significant at moderate Q2. Upcoming JLab SIDIS experiments at 6 and 12 GeV will significantly improve the statistical precision of polarized target data, allowing studies of correlations between longitudinal and transverse degrees of freedom Measurements  of TMDs at JLab in the valence region provide important input into the global analysis of Transverse Momentum Distributions (involving HERMES,COMPASS,RHIC,BELLE,BABAR+JPARC,GSI,EIC) Jlab, June 18, 2010

  21. Support slides…. 21 Jlab, June 18, 2010 JLab, Nov 25

  22. 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 Jlab, June 18, 2010

  23. e p 5-7 GeV 50-150 GeV - Boer-Mulders Asymmetry with CLAS12 & EIC Transversely polarized quarks in the unpolarized nucleon CLAS12 sin(fC) =cos(2fh) EIC Nonperturbative TMD Perturbative region CLAS12 and ELIC studies of transition from non-perturbative to perturbative regime will provide complementary info on spin-orbit correlations and test unified theory Jlab, June 18, 2010

  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 Jlab, June 18, 2010

  25. A1 PT-dependence Anselmino Collins CLAS data suggests that width of g1 is less than the width of f1 Jlab, June 18, 2010

  26. 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) Jlab, June 18, 2010

  27. sUL ~ KM Collins fragmentation: Longitudinally polarized target Transversely polarized quarks in the long. polarized nucleon Kotzinian-Mulders Asymmetry curves, cQSM from Efremov et al • KM sin2f moment, sensitive to spin-orbit correlations: the only leading twist azimuthal moment for longitudinally polarized target • More info will be available from SIDIS (COMPASS,EIC) and DY (RHIC,GSI) Jlab, June 18, 2010

  28. 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. 28 Jlab, June 18, 2010

  29. CLAS configurations ep→e’pX Inner Calorimeter e p- p+ Transversely polarized target Longitudinaly polarized target • Polarized NH3/ND3 (no IC, ~5 days) • Polarized NH3/ND3 with IC 60 days • Polarized HD-Ice (no IC, 25 days) • Polarizations: • Beam: ~80% • NH3 proton 80%,ND3 ~30% • HD (H-75%,D-25%) 29 Jlab, June 18, 2010

  30. Polarized target Helium tube Inner Calo CLAS Longitudinally polarized target run (eg1-dvcs) Jlab, June 18, 2010

  31. 7.5mm eg1-dvcs Run Conditions Beam polarization: >80% Target polarization: >75% Rastering: R=~7.mm eg1-dvcs Inner Calo Polarized target Helium tube Jlab, June 18, 2010

  32. eg1-dvcs: Monitoring polarizations HWP→IN HWP→OUT Monitoring the time dependence of the beam polarization using the single spin asymmetry in ep→e’pX Monitoring the time dependence of the product of target and beam polarizations using the elastic asymmetry Jlab, June 18, 2010

  33. 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 33 Jlab, June 18, 2010

  34. e1&eg1-dvcs: Monitoring and calibration IC operating in high background was stable. IC time and energy resolutions resolutions after calibration using 2 photon events. Jlab, June 18, 2010

  35. SSA with long. polarized target quark polarization Jlab, June 18, 2010

  36. SSA with long. polarized target quark polarization Jlab, June 18, 2010

  37. SSA with unpolarized target quark polarization Jlab, June 18, 2010

  38. SSA with unpolarized target quark polarization Jlab, June 18, 2010

  39. 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. Jlab, June 18, 2010

  40. 40 JLab, Nov 25 Jlab, June 18, 2010

  41. CLAS vs CLAS12? • Existing inconsistencies between HERMES and COMPASS require new independent input. CLAS data will be crucial in developing global analysis of 3D parton distributions, TMDs GPDs and Wigner distributions. • Study the Q2 dependence of different SSA at fixed Bjorken-x will require measurements with different beam energies, including 6 GeV. • Virtual photon has some angle with beam direction, so measurements with longitudinal and transverse target are important for each other. • Enables early understanding of higher order corrections and higher twist contributions. • CLAS data at 6 GeV will be important to analyze future CLAS12 data (different systematics). • Reaction asymmetries from events ray traced back to vertex gives tomographic decomposition of target polarization vs e running time. -> essential to optimize plans for 12 GeV experiments 41 Jlab, June 18, 2010 JLab, Nov 25

  42. 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) 42 Jlab, June 18, 2010 JLab, Nov 25

  43. SSA with unpolarized target quark polarization 43 Jlab, June 18, 2010 JLab, Nov 25

  44. SSA with unpolarized target quark polarization 44 Jlab, June 18, 2010 JLab, Nov 25

  45. SSA with unpolarized target quark polarization 45 Jlab, June 18, 2010 JLab, Nov 25

  46. SSA with unpolarized target quark polarization 46 Jlab, June 18, 2010 JLab, Nov 25

  47. Beam SSA: ALU from CLAS @ JLab Photon Sivers Effect Afanasev & Carlson, Metz & Schlegel Beam SSA from initial distribution(Boer-Mulders TMD) F.Yuan using h1┴ from MIT bag model 5.7 GeV p+ 4.3 GeV p+ 5.7 GeV p0 0.5<z<0.8 Beam SSA from hadronization (Collins effect) by Schweitzer et al. Beam SSA for p0 and p+ are comparable indicating small Collins type contributions 47 47 Jlab, June 18, 2010 JLab, Nov 25

  48. Inbendin/outbending configurations Different polarities increase the acceptance of positive and negative hadrons. 48 Jlab, June 18, 2010 JLab, Nov 25

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