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

3D structure of the nucleon TMDs Semi-Inclusive processes and transverse momentum distributions 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

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 One of the biggest surprises from lattice was significant dependence of transverse momentum distributions on the spin orientation. You can see that ratio of u+(quark spin aligned with proton)/u- and quark spin antialigned is going down with K_T of the quark. distributions of PDFs may depend on flavor and spin (lower fraction aligned with proton spin at large kT,bT) 3 Avakian, Jlab May 28

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

3D structure: GPDs epe’pp0 CLAS e1dvcs Lattice (QCDSF) DVCS asymmetries measured at HERMES & JLAB More measurements at JLab, Compass using the handbag approach based on factorization in hard parton subprocesses and soft generalized parton distributions (GPDs) GPDs describing unpolarized and longitudina;ly polarized quarks can be accessed in the DVCS process. Transverse photon dominates the x-section for exclusive p0 production Spin-azimuthal asymmetries in hard exclusive production of photons and pions give access to underlying GPDs H. Avakian, JLab, Jan 23

Unpolarized beam, longitudinal target (TSA) : ~ t-dependence of H Unpolarized beam, longitudinal target (TSA) : DsUL ~ sinfIm{F1H +x(F1+F2)(H + xB/2E) –xkF2 E+…}df ~ Im{Hp, Hp} H. Avakian, JLab, Jan 23

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

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

flavor decomposition of underlying chiral-odd GPDs. 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

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

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

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

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

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

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

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 DVCS 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

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

Exclusive p0 rates higher for small W sT – dominates for p0. dsT /dt dsL /dt K2⊥/Q2 corrections 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

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

Transverse densities in the nucleon in nuclear matter Quark transverse charge densities inside an unpolarized proton arXiv:1304.5926 Skyrme model proton medium in-medium modied Skyrme model. 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

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