Related papers: Quark spin-orbit correlations
To understand orbital-angular-momentum contributions is becoming crucial for clarifying nucleon-spin issue in the parton level. Twist-two structure functions b_1 and b_2 for spin-one hadrons could probe orbital-angular-momentum effects,…
I review what is known about the quark and gluon spin distributions in the nucleon. I discuss in some detail (a) the existence of sum rules for angular momentum; (b) the interpretation and possible measurement of the nucleon's transversity…
We discuss the recent interpretation of quark distribution functions in the plane transverse to the light-cone direction. Such a mapping is model independent and allows one to build multidimensional pictures of the hadron and to develop a…
Several examples for the role of orbital angular momentum and spin-orbit correlations in hadron structure are discussed.
We present the first calculation in lattice QCD of the lowest two moments of transverse spin densities of quarks in the nucleon. They encode correlations between quark spin and orbital angular momentum. Our dynamical simulations are based…
We examine the single-spin asymmetry (SSA) caused by the five-quark components of the proton for semi-inclusive electroproduction of charged pions in deep-inelastic scattering on a transversely polarized hydrogen target. The large SSA is…
The polarized distribution functions of mesons, including pion, kaon and eta, using the proton structure function, are calculated. We are looking for a relationship between the polarized distribution of mesons and the polarized structure of…
We study the quark helicity distributions at large x in perturbative QCD, taking into account contributions from the valence Fock states of the nucleon which have nonzero orbital angular momentum. These states are necessary to have a…
In this brief note insightful remarks are made on the controversy on the decomposition of the proton spin into the spin and orbital angular momenta of quarks and gluons. It is argued that the difference in the perception on the nature of…
The phenomenological motivations, the expressions and the comparison with experiment of the parton distributions inspired by the quantum statistics are described. The Fermi-Dirac expressions for the quarks and their antiparticles…
Based on quantum fluctuations in momentum and of the proton into meson-baryon pairs, we develop a physical model for the non-perturbative x-shape of parton density functions in the proton. The model describes the proton structure function…
We check the $u$ and $d$ quark contributions to the spin content of the $\Lambda$ by means of the $q\to\Lambda$ fragmentation and find that the $u$ and $d$ quarks of the $\Lambda$ are likely positively polarized. The parton distributions in…
We study the Wigner functions of the nucleon which provide multidimensional images of the quark distributions in phase space and combine in a single picture all the information contained in the generalized parton distributions (GPDs) and…
We extract the individual contributions from u and d quarks to the Dirac and Pauli form factors of the proton, after a critical examination of the available measurements of electromagnetic nucleon form factors. From this data we determine…
We investigate the interaction of strong color fields in the glasma stage of high-energy nuclear collisions with the spins of quarks and antiquarks. We employ the perturbative solution of the quantum kinetic theory for the spin transport of…
We have examined the spin structure of the proton in the region of the nucleon resonances (1.085 GeV < W < 1.910 GeV) at an average four momentum transfer of Q^2 = 1.3 GeV^2. Using the Jefferson Lab polarized electron beam, a spectrometer,…
In the past year, polarized deep inelastic scattering experiments at CERN and SLAC have obtained structure function measurements off proton, neutron and deuteron targets at a level of precision never before achieved. The measurements can be…
The general parameterization of the quark-quark correlation function for a spin-1/2 hadron is considered. The presence of the Wilson line ensuring color gauge invariance of the correlator induces structures that were not given explicitly in…
It is shown that the momentum density of free electromagnetic field splits into two parts. One has no contribution to the net momentum due to the transversality condition. The other yields all the momentum. The angular momentum that…
The proton spin puzzle denotes the challenge of describing the proton's spin in terms of the angular momenta of the quarks and gluons which comprise it. These quarks and gluons carry a fraction $x$ of the proton's momentum. Contributions…