Studies of spin-orbit correlations at JLAB

Studies of single spin asymmetries for pion electroproduction in semi-inclusive deep-inelastic scattering are presented using the polarized \sim6 GeV electrons from at the Thomas Jefferson National Accelerator Facility (JLab) and the Continuous Electron Beam Accelerator Facility (CEBAF) Large Acceptance Spectrometer (CLAS) with the Inner Calorimeter. The cross section versus the azimuthal angle {\phi}_h of the produced neutral pion has a substantial sin {\phi}_h amplitude. The dependence of this amplitude on Bjorken x_B and on the pion transverse momentum is extracted and compared with published data.Comment: proceedings of SPIN2010 conference (September-October 2010, Juelich-Germany

Deep exclusive charged π\pi electroproduction above the resonance region

A description of exclusive charged pion electroproduction $(e,e'\pi^{\pm})$ off nucleons at high energies is proposed. The model combines a Regge pole approach with residual effect of nucleon resonances. The exchanges of $\pi$(140), vector $\rho(770)$ and axial-vector $a_1(1260)$ and $b_1(1235)$ Regge trajectories are considered. The contribution of nucleon resonances is described using a dual connection between the exclusive hadronic form factors and inclusive deep inelastic structure functions. The model describes the measured longitudinal, transverse and interference cross sections at JLAB and DESY. The scaling behavior of the cross sections is in agreement with JLAB and deeply virtual HERMES data. The results for a polarized beam-spin azimuthal asymmetry in $(\vec{e},e'\pi^{\pm})$ are presented. Model predictions for JLAB at 12 GeV are given.Comment: 29 page

Constraints on spin-dependent parton distributions at large x from global QCD analysis

We investigate the behavior of spin-dependent parton distribution functions (PDFs) at large parton momentum fractions x in the context of global QCD analysis. We explore the constraints from existing deep-inelastic scattering data, and from theoretical expectations for the leading x -> 1 behavior based on hard gluon exchange in perturbative QCD. Systematic uncertainties from the dependence of the PDFs on the choice of parametrization are studied by considering functional forms motivated by orbital angular momentum arguments. Finally, we quantify the reduction in the PDF uncertainties that may be expected from future high-x data from Jefferson Lab at 12 GeV.Comment: 14 pages, 3 figures, 1 tabl

Fully Differential Monte-Carlo Generator Dedicated to TMDs and Bessel-Weighted Asymmetries

We present studies of double longitudinal spin asymmetries in semi-inclusive deep inelastic scattering using a new dedicated Monte Carlo generator, which includes quark intrinsic transverse momentum within the generalized parton model based on the fully differential cross section for the process. Additionally, we apply Bessel-weighting to the simulated events to extract transverse momentum dependent parton distribution functions and also discuss possible uncertainties due to kinematic correlation effects.Comment: 3rd Workshop on the QCD Structure of the Nucleon (QCD-N'12) October 22-26, 2012, Bilbao, Spai

New results on SIDIS SSA from Jefferson Lab

We present studies of single-spin and double-spin asymmetries in semi-inclusive electroproduction of pions using the CEBAF 6 GeV polarized electron beam. Kinematic dependences of single and double spin asymmetries have been measured in a wide kinematic range at CLAS with a polarized NH$_3$ target. Significant target-spin $\sin2\phi$ and $\sin\phi$ asymmetries have been observed. The hypothesis of factorization has been tested with $z$-dependence of the double spin asymmetry.Comment: 4 pages, 6 figure

Beam spin asymmetry in deeply virtual π\pi production

An interpretation of the beam spin azimuthal asymmetries measured at JLAB in deep exclusive electroproduction of charged and neutral pions is presented. The model combines a Regge pole approach with the effect of nucleon resonances. The $s$- and $u$-channel contributions are described using a dual Bloom-Gilman connection between the exclusive form factors and inclusive deep inelastic structure functions. The results are in agreement with data provided the excitations of nucleon resonances are taken into account.Comment: 5 pages, 3 figures. Talk at the 19th International Spin Physics Symposium (SPIN2010), Sept.27-Oct.2, 2010, Juelich, German

Quark orbital angular momentum: can we learn about it from GPDs and TMDs?

It is known how to access information on quark orbital angular momentum from generalized parton distribution functions, in a certain specified framework. It is intuitively expected, that such information can be accessed also through transverse momentum dependent distribution functions, but not known how. Now quark models provide promising hints. Recent results are reviewed.Comment: proceeding of the "4th Workshop on Exclusive Reactions at High Momentum Transfer," 18-21 May 2010, Jefferson La

Predictions for Sivers single spin asymmetries in one- and two-hadron electroproduction at CLAS12 and EIC

The study of the Sivers effect, describing correlations between the transverse polarization of the nucleon and its constituent (unpolarized) parton's transverse momentum, has been the topic of a great deal of experimental, phenomenological and theoretical effort in recent years. Semi-inclusive deep inelastic scattering measurements of the corresponding single spin asymmetries (SSA) at the upcoming CLAS12 experiment at JLab and the proposed Electron-Ion Collider will help to pinpoint the flavor structure and the momentum dependence of the Sivers parton distribution function describing this effect. Here we describe a modified version of the $\tt{PYTHIA}$ Monte Carlo event generator that includes the Sivers effect. Then we use it to estimate the size of these SSAs, in the kinematics of these experiments, for both one and two hadron final states of pions and kaons. For this purpose we utilize the existing Sivers parton distribution function (PDF) parametrization extracted from HERMES and COMPASS experiments. Using this modified version of $\tt{PYTHIA}$, we also show that the the leading order approximation commonly used in such extractions may provide significantly underestimated values of Sivers PDFs, as in our Monte Carlo simulations the omitted parton showers and non-DIS processes play an important role in these SSAs, for example in the COMPASS kinematics.Comment: 18 pages, 27 figures. V2: updated to version published in PRD, two references have been added and some minor changes done to the tex