Related papers: Valence Quark Polarization In the Nucleon And the …
The spin 1/2 baryons are pictured as a composite system made out of a "core" of three valence quarks (as in the simple quark model) surrounded by a "sea" (of gluon and $q\bar{q}$ pairs) which is specified by its total quantum numbers. We…
I calculate the quark contributions to the axial and tensor charges and the spin structure of the proton. The result indicates that the valence current quark spins carry 1/3 of the proton spin, the total contribution of quark spins to the…
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…
Scattering of protons with transversal polarization $p_y^p$ on deuterons with tensor polarization $P_{xz}$ provides a null-test signal for time-reversal (T) invariance violating but parity (P) conserving effects. We calculate the…
We show that the contact couplings of neutral pseudoscalar and axial mesons to the nucleon are proportional to $\Delta s$, the fraction of nucleon spin carried by the strange quark sea, and thus are strongly suppressed relative to the…
We investigate the possibility to measure the spin content carried by the different quark flavors in a nucleon by means of polarized deep inelastic scattering with $W^\pm$ exchange at HERA. Such measurements require a polarized proton beam.…
The quark-gluon plasma produced by collisions between ultra-relativistic heavy nuclei is well described in the language of hydrodynamics. Non-central collisions are characterized by very large angular momentum, which in a fluid system…
Recent precision spin structure data from Jefferson Lab have significantly advanced our knowledge of nucleon structure in the valence quark (high-$x$) region and improved our understanding of higher-twist effects, spin sum rules and…
We start from an MIT-bag model calculation which provides information about the constituent quark distributions in the nucleon. The constituent quarks, however, are themselves considered as complex objects whose partonic substructure is…
Deep inelastic polarized and unpolarized structure functions for a free nucleon are obtained in a modified Center-of-Mass bag model, which includes the symmetry breaking effects from spin-dependent interactions. The quark distribution…
The spin-dependent structure function of the deuteron, g_1D, is calculated within a covariant framework. The off-shell structure of the bound nucleon gives corrections to the convolution model at a level of half a percent for x below 0.7,…
In the Framework of {\it{valon model}} we have calculated the parton distribution in a valon for both the polarized and unpolarized cases. These distributions are originated purely from the dressing of a valence quark in QCD and are common…
Since the announcement of the proton spin crisis by the European Muon Collaboration there has been considerable progress in unravelling the distribution of spin and orbital angular momentum within the proton. We review the current status of…
In recent decades, the spin and transverse momentum of quarks and gluons were found to play integral roles in the structure of the nucleon. Simultaneously, the onset of gluon saturation in hadrons and nuclei at high energies was predicted…
One of the main aims of the COMPASS experiment at CERN is the study of the spin structure of the nucleon and in particular the determination of the gluon polarization in the nucleon. We present some new results of 2002-2003 data analysis.…
We have studied the spin polarization of $\Lambda$ hyperons in heavy ion collisions at center-of-mass energies $\sqrt{s_{NN}} = 200$ GeV and $\sqrt{s_{NN}} = 5.02$ TeV carried out at RHIC and LHC colliders. We have calculated the mean spin…
Using a simple picture of the constituent quark as a composite system of point-like partons, we construct the polarized parton distributions by a convolution between constituent quark momentum distributions and constituent quark structure…
A first evaluation of the polarized valence quark distribution $\Delta u_v(x)+\Delta d_v(x)$ from the COMPASS experiment (CERN/SPS) is presented. The data were collected by COMPASS in the years 2002--2004 using a 160 GeV polarized muon beam…
The spin and orbital angular momentum carried by different quark flavors in the nucleon are calculated in the SU(3) chiral quark model with symmetry-breaking. The model is extended to all octet and decuplet baryons. In this model, the…
Based on a simple model which is compatible with the idea of the static quark model and the parton model, the polarized structure functions of proton and deuteron, two-spin asymmetries of $\pi ^0$ in polarized $pp$ reactions and inelastic…