Transverse distributions of polarized quarks

1. Transverse distributions of polarized quarks Harut Avakian (JLab) January 22-24, 2015 Thomas Jefferson National Accelerator Facility H. Avakian, JLab, Jan 23

2. Semi-Inclusive processes and transverse momentum distributions h TMDs 3D structure of the nucleon up down Hard exclusive processes and spatial distributions of partons Pasquini & Yuan g,h GPDs Combination of polarized and unpolarized targets and large acceptance coverage of CLAS12 allows studies of GPDs in a wide kinematic range. (QCDSF) H. Avakian, JLab, Jan 23

3. Quark distributions at large kT: lattice B.Musch et al arXiv:1011.1213 g1q=Dq=(q+-q-)/2 B.Pasquini et al arXiv:0705.4345 distributions of PDFs may depend on flavor and spin (lower fraction aligned with proton spin at large kT,bT) 3 Avakian, Jlab May 28

4. Flavor separation of form factors Quark transverse charge densities inside an unpolarized proton arXiv:1304.5926 space distributions depend on flavor and spin (modify in medium) G. Cates et al. PRL 106 (2011) 252003 Q4F2q/k Q4 F1q G. Miller et al (2011 ) • form factors of the nucleon fell off faster in nuclear matter H. Avakian, JLab, Jan 23

5. 3D structure: GPDs epe’pp0 CLAS e1dvcs DVCS asymmetries measured at HERMES & JLAB More measurements at JLab, Compass Transverse photon dominates the x-section for exclusive p0 production Lattice (QCDSF) Spin-azimuthal asymmetries in hard exclusive production of photons and pions give access to underlying GPDs H. Avakian, JLab, Jan 23

6. ~ Unpolarized beam, longitudinal target (TSA) : ~ ~ Im{Hp, Hp} DsUL ~ sinfIm{F1H +x(F1+F2)(H+ xB/2E) –xkF2E+…}df t-dependence of H H. Avakian, JLab, Jan 23

7. t-dependences of HT epe’pp0 Goldstein, Liuti et al P.Kroll & S. Goloskokov • The production amplitude at large Q2 factorizes into the hard subprocess and GPDs • Within the handbag approach g*Tp transitions are related to transversity (helicity-flip) GPDs accompanied by a twist-3 pion wave function Hard partonic subprocess A.Kim’s talk • CLAS12 can measure Q2 dependence of HT SSAs significantly extending the range of CLAS H. Avakian, JLab, Jan 23

8. Studies of Chiral-Odd GPDs in Hard Exclusive PseudoscalarMeson Production Using the CLAS12 Detector PAC42 LoI H. Avakian, JLab, Jan 23

9. Outline We propose a combination of measurements of cross sections, spin and azimuthal asymmetries with a longitudinally polarized beam and both unpolarized and longitudinally polarized proton target providing a flavor decomposition of underlying chiral-odd GPDs. • Exclusive production of pseudoscalar mesons • Chiral-Odd GPDs and transverse photon • Studies of Transversity and GPD ET • Exclusive kaon production and separation of different channels _ H. Avakian, JLab, Jan 23

10. Exclusive kaon production Unlike p+ the K+ x-section is totally dominated by the transverse photon pole contribution negligible Exclusive production of KL and KS provide access to different combinations of chiral-odd GPDs H. Avakian, JLab, Jan 23

11. SSAs in exclusive kaon production Goloskokov&Kroll KS asymmetries are predicted to be large and with opposite sign to KL Goldstein, Hernandez, & Liuti Beam and target asymmetries in exclusive production of KL and KS are very sensitive to chiral-odd GPDs. H. Avakian, JLab, Jan 23

12. K/K* and L/S separation L S Due to detector resolution clean separation of different channels (L,S,K*) will require detection of 4 particles H. Avakian, JLab, Jan 23

13. K+ L/S separation K+ Detection of K+ p and p- would allow to separate of different final states (L,S,K*) q L H. Avakian, JLab, Jan 23

14. Exclusive L/S separation L S Detection of the complete final sate allow separation of exclusive Ss H. Avakian, JLab, Jan 23

15. 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, Glasgow, May 13

16. Summary • Understanding of transverse space distributions of polarized quarks is crucial for interpretation of exclusive production of photons and pions • Identification of Kaons will significantly enhance CLAS12 capabilities to study exclusive processes involving kaons. • Combination of exclusive kaon and pion measurements from CLAS12 with unpolarized, longitudinally and transversely polarized targets would allow studies of chiral-odd GPDs • Measurements of hard-exclusive production of photons and pseudoscalar mesons will help to accomplish the CLAS12 program of studies of the 3D structure of the nucleon Nead GPD/CFF extraction framework with controlled systematics. H. Avakian, JLab, Jan 23

17. Support slides…. H. Avakian, JLab, Jan 23

18. Exclusive p0 rates higher for small W sT – dominates for p0. dsT /dt dsL /dt K2⊥/Q2corrections in the propagators of the hard subprocess amplitude are essential in the description of the cross section at low Q2. They decrease s by a factor of about 10 at Q2∼ 3GeV2 M 0+,++ amplitude is important in s T . H. Avakian, JLab, Jan 23

19. Exclusive p+ cross sections in modified perturbative approach • For π+ production the p → n transition GPDs are required which are given by the isovector combination of proton GPDs F(3) = Fu − Fd . • The γ∗q → πq subprocess amplitudes within the modified perturbative approach is defined Fourier transform to b space momentum fraction of the quark defined with respect to the meson momentum transverse cross section for large t (−t>∼ 0.2 GeV2) is larger than the longitudinal one H. Avakian, JLab, Jan 23

20. Transverse densities in the nucleon in nuclear matter Quark transverse charge densities inside an unpolarized proton arXiv:1304.5926 Skyrme model proton medium • form factors of the nucleon fell off faster in nuclear matter • the size of the nucleon tends to bulge out in nuclear matter. H. Avakian, JLab, Jan 23

21. Exclusive p+/p0 arXiv:0906.0460 Different transverse moments will give access to different combinations of GPDs H. Avakian, JLab, Feb 24