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Transversity program at CLAS

Transversity program at CLAS. H.Avakian (JLab). GPD-2010 Trento, Oct 11-15. Physics motivation k T -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

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Transversity program at CLAS

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  1. Transversity program at CLAS H.Avakian (JLab) GPD-2010 Trento, Oct 11-15 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 Summary H. Avakian, Trento, Oct 11

  2. 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 How spin-orbit correlations are related to the longitudinal structure and nuclear effects? H. Avakian, Trento, Oct 11

  3. 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. 3 3 H. Avakian, Trento, Oct 11

  4. 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)… x-kT and x-rT correlations define the final x-distributions d2kT d2rT PDFsq(x), Dq(x)… In nuclear env. TMDs and GPDs modify 4 H. Avakian, Trento, Oct 11

  5. Nucleon TMDs quark polarization + Higher twist distribution functions 5 H. Avakian, Trento, Oct 11

  6. SIDIS kinematical plane and observables Target polarization Cross section is a function of scale variables x,y,z U unpolarized L long.polarized T trans.polarized z Beam polarization sin2f moment of the cross section for unpolarized beam and long. polarized target 6 H. Avakian, Trento, Oct 11

  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, Trento, Oct 11

  8. 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%) 8 H. Avakian, Trento, Oct 11

  9. 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. 9 H. Avakian, Trento, Oct 11

  10. 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, Trento, Oct 11

  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, Trento, Oct 11

  12. Quark distributions at large kT: lattice q Dq JMR model MR, R=s,a B.Musch arXiv:0907.2381 Du/u (dipole formfactor), J.Ellis, D-S.Hwang, A.Kotzinian 12 12 12 H. Avakian, Trento, Oct 11

  13. Quark distributions vs bT B.Musch arXiv:0907.2381 Difference in final distributions when using f1,g1 or q+,q- What we gain modeling + and – distributions for GPDs? 13 13 13 H. Avakian, Trento, Oct 11

  14. 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 14 14 H. Avakian, Trento, Oct 11

  15. 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+ 15 15 H. Avakian, Trento, Oct 11

  16. 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, Trento, Oct 11

  17. 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. Collins contribution should be suppressed → g┴ wanted !!! H. Avakian, Trento, Oct 11

  18. 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, Trento, Oct 11

  19. r+ p+ SSA from r Modulation exist even for vanishing helicity change amplitudes r0 p+ SSA has a significant dependence on the source process H. Avakian, Trento, Oct 11

  20. Exclusive pion beam SSA @CLAS6 Sign flip at z ~ 0.5 At z<0.5 struck quark in neutron H. Avakian, Trento, Oct 11

  21. HT and Semi-Exclusive Pion Production Fragmentationp+ p+ p0 HT effects and exclusive p0 suppressed A.Afanasev, C.Carlson, C. Wahlquist Phys.Lett.B398:393-399,1997 Dominant contribution to meson wave function is a perturbative one gluon exchange and approach its validity at factor ~3 lower Q2 than in case of hard exclusive scattering. How big is the rho semi-exclusive production compared to pion? 21 H. Avakian, Trento, Oct 11

  22. GPDs from cross section ratios M.Diehl et al. hep-ph/0506171 K*+ K+ • Study ratio observables: K/K*/r+,polarization transfer • Different final state mesons filter out different combinations of unpolarized (H,E) and polarized (H,E) GPDs. H. Avakian, Trento, Oct 11

  23. 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 23 H. Avakian, Trento, Oct 11

  24. 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 24 H. Avakian, Trento, Oct 11

  25. 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) 25 H. Avakian, Trento, Oct 11

  26. Quark distributions at large kT PT = p┴+zkT bigger effect at large z Higher probability to find a hadron at large PT in nuclei kT-distributions may be wider in nuclei? Understanding of modification of kT widths in nuclei is important also for nucleon TMDs 26 26 H. Avakian, Trento, Oct 11

  27. kT and FSI l’ l total transverse momentum broadening squared x,k’T l’T spectator system nucleus Tang,Wang & Zhou Phys.Rev.D77:125010,2008 l l’ BHS 2002 Collins 2002 Ji,Yuan 2002 x,kT lT spectator system proton soft gluon exchanges included in the distribution function (gauge link) • The difference is coming from final state interactions (different remnant) • Studies of DIS and SIDIS with nuclear targets provide info on kT 27 H. Avakian, Trento, Oct 11

  28. Modification of Cahn effect Bag model Gao, Liang & Wang arXiv:1001.3146 • Nuclear modification of Cahn may provide info on kT broadening and proton TMDs 28 28 H. Avakian, Trento, Oct 11

  29. LTCC DC R1, R2, R3 CHL-2 PCAL CLAS12 Beam Current: 90 µA Max Pass energy: 2.2 GeV Max Enery Hall A,B,C: 11 GeV Solenoid 5T Primary goal of experiments using CLAS12: study of the internal nucleon dynamics by accessing GPDs & TMDs  detector tuned for studies of exclusive and semi-inclusive reactions in a wide kinematic range. Large acceptance detector and high luminosity capabilities EC HTCC FTOF L = 1035 cm-2s-1 CEBAF @ 12 GeV and CLAS12 May 2012 6 GeV Accelerator Shutdown starts May 2013 Accelerator Commissioning starts 2013-2015 Pre-Ops (beam commissioning) H. Avakian, Trento, Oct 11

  30. 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 Project under development H. Avakian, Trento, Oct 11

  31. K/K* and L/S separations Detection of K+ crucial for separation of different final states (L,S,K*) H. Avakian, Trento, Oct 11

  32. 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 H. Avakian, Trento, Oct 11

  33. Longitudinally polarized target: Double spin asymmetries H. Avakian, Trento, Oct 11

  34. 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 H. Avakian, Trento, Oct 11

  35. 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. B. Pasquini et al. arXiv:0806.2298 H. Avakian, Trento, Oct 11

  36. 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, Trento, Oct 11

  37. A.Kotzinian High statistics of CLAS12 will allow studies of kinematic dependences of the Sivers effect in target fragmentation region Sivers effect in the target fragmentation xF>0 (current fragmentation) xF<0 (target fragmentation) h M Fracture Functions H. Avakian, Trento, Oct 11

  38. L production in the target fragmentation L polarization in TFR provides information on contribution of strange sea to proton spin (ud)-diquark is a spin and isospin singlet s-quark carries whole spin of L xF- momentum in the CM frame xF(L) Sivers-2009 Study polarized diquark fracture functions sensitive to the correlations between struck quark transverse momentum and the diquark spin. EIC CLAS12 Combination of CLAS12 and EIC would allow studies of hadronization in the target fragmentation region (fracture functions) in a wide range of x 38 H. Avakian, Trento, Oct 11

  39. Deeply Virtual Compton Scattering ep→e’p’g Polarized beam, unpolarized target: ~ DsLU~ sinf{F1H( x,x,t)+ x(F1+F2)H+kF2E} Kinematically suppressed Unpolarized beam, longitudinal target: ~ DsUL~ sinf{F1H+x(F1+F2)(H+.. } DVCS BH Kinematically suppressed Unpolarized beam, transverse target: DsUT~ cosf{k(F2H – F1E) + …..} x = xB/(2-xB ),k = t/4M2 Kinematically suppressed GPD combinations accessible as azimuthal moments of the total cross section. H. Avakian, Trento, Oct 11

  40. CLAS12-DVCS/BH Target Asymmetry e p epg Transversely polarized target Sample kinematics E = 11 GeV Q2=2.2 GeV2, xB = 0.25, -t = 0.5GeV2 DsUT~ cosfIm{k1(F2H– F1E) +…}df AUTx Target polarization in scattering plane AUTy Target polarization perpendicular to scattering plane DVCS Transverse asymmetry (function of momentum transfer to proton) is large and has strong sensitivity to GPD-E Meissner, Metz & Goeke (2007) H. Avakian, Trento, Oct 11

  41. 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, Trento, Oct 11

  42. Support slides…. H. Avakian, Trento, Oct 11

  43. SSA in ep->e’pX HERMES 27.5 GeV CLAS 5.7 GeV Strange pattern: p0 SSA bigger at very low and very large z H. Avakian, Trento, Oct 11

  44. Quark distributions at large kT bigger effect at large z PT = p┴+zkT Higher probability to find a hadron at large PT in nuclei kT-distributions may be wider in nuclei? Understanding of modification of kT widths in nuclei is important also for nucleon TMDs 44 44 H. Avakian, Trento, Oct 11

  45.   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, Trento, Oct 11

  46. 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, Trento, Oct 11

  47. + K+ - K- epe’K+X • K+ ampl. >p+ampl. • Unespected from u-quark dominance! • How large can the effect of s quarks be? S.Arnold et al. 0805.2137 /K measurement @ CLAS12 will provide a more detailed knowledge of Sivers effect M. Anselmino et al. 0805.2677 Kaon TMDs program @ 12 GeV in Hall B HERMES coll. PRL 103 (2009) H. Avakian, Trento, Oct 11

  48. kT and FSI l’ l total transverse momentum broadening squared x,k’T l’T spectator system nucleus Tang,Wang & Zhou Phys.Rev.D77:125010,2008 l l’ BHS 2002 Collins 2002 Ji,Yuan 2002 x,kT lT ~4 n, with ~4-6 MeV spectator system proton soft gluon exchanges included in the distribution function (gauge link) • The difference is coming from final state interactions (different remnant) • Studies of DIS and SIDIS with nuclear targets provide info on kT 48 H. Avakian, Trento, Oct 11

  49. Anselmino et al from EMC data → = 0.25 Wider at smaller beam energies? Transverse momentum distributions of hadrons Gauss CLAS slightly lower, but may have bigger 49 H. Avakian, Trento, Oct 11

  50. 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. 50 H. Avakian, Trento, Oct 11

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