Related papers: Proton spin content and QCD topological susceptibi…
We consider the cross section of the deep inelastic pion electroproduction on a proton target at threshold for Q^2 in the region 5-10 GeV^2. The corresponding amplitudes are described in terms of two form factors which we calculate using…
The proton is a composite object with spin one-half, understood to contain highly relativistic spin one-half quarks exchanging spin-one gluons, each possibly with significant orbital angular momenta. While their fundamental interactions are…
In light of recent experimental progress in determining the pressure and shear distributions in the proton, these quantities are calculated in a model with confined quarks supplemented by the pion field required by chiral symmetry. The…
Spin effects in exclusive and inclusive reactions provide an essential new dimension for testing QCD and unraveling hadron structure. Remarkable new experiments from SLAC, HERMES (DESY), and the Jefferson Laboratory present many challenges…
A dominant QCD mechanism for the single transverse-spin asymmetry in hard processes is induced by the twist-3 quark-gluon correlations inside nucleon, combined with the soft-gluonic poles to produce the interfering phase for the associated…
We report the measurement of near threshold neutral pion electroproduction cross sections and the extraction of the associated structure functions on the proton in the kinematic range $Q^2$ from 2 to 4.5 GeV$^2$ and $W$ from 1.08 to 1.16…
We calculate the twist-4 corrections to the integral of $g_1(x,Q^2)$ in the framework of QCD sum rules using an interpolating nucleon field which contains explicitly a gluonic degree of freedom. This information can be used together with…
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…
The near threshold photo or electroproduction of heavy vector quarkonium off the proton is studied in quantum chromodynamics. Similar to the high-energy limit, the production amplitude can be factorized in terms of gluonic Generalized…
Precise measurements of the spin structure functions of the proton $g_1^p(x,Q^2)$ and deuteron $g_1^d(x,Q^2)$ are presented over the kinematic range $0.0041 \leq x \leq 0.9$ and $0.18 $ GeV$^2$ $\leq Q^2 \leq 20$ GeV$^2$. The data were…
We report first calculations of the topological susceptibility measured using the field theoretic method on SU(3) gauge configurations produced by the UKQCD collaboration with two flavours of dynamical, improved, Wilson fermions. Using…
Nontrivial $q \bar q$ sea effects have their origin in the low-$Q^2$ dynamics of strong QCD. We present here a quark model calculation of the contribution of $s \bar s$ pairs arising from a {\it complete} set of OZI-allowed strong $Y^*K^*$…
It is shown that the proton spin problem raised by the Ellis-Jaffe sum rule violation does not in conflict with the SU(6) quark model, provided that the relativistic effect from the quark transversal motions, the flavor asymmetry between…
This paper contains three parts relating to the nucleon spin structure in a simple picture of the nucleon: (i) The polarized gluon distribution in the proton is dynamically predicted starting from a low scale by using a nonlinear QCD…
The electromagnetic form factors of the proton are obtained using a particular realization of QCD in the large $N_c$ limit (${QCD}_{\infty}$), which sums up the infinite number of zero-width resonances to yield an Euler's Beta function…
A proton spin-polarizability characterizing backward Compton scattering has been extracted from a dispersion analysis of data between 33 and 309 MeV. This backward spin-polarizability, "delta" = 27.1 +/-2.2(stat+sys) +2.8/-2.4(model) in…
We perform the first Lattice calculation about the charmed hadron spin decomposition using overlap fermions on a 2+1 flavor RBC/UKQCD domain-wall gauge configurations at 0.083 fm with 300 MeV pion mass. It is found that the contributions of…
The preliminary STAR data for proton cumulants for central collisions at \sqrt{s}=7.7 GeV are consistent with a two-component proton multiplicity distribution. We show that this two-component distribution is statistics friendly in that…
We present the results of our final analysis of the full data set of g_1^p(Q^2), the spin structure function of the proton, collected using CLAS at Jefferson Lab in 2000-2001. Polarized electrons with energies of 1.6, 2.5, 4.2 and 5.7 GeV…
We consider several single spin asymmetries in inclusive, transversely polarized proton(antiproton) - proton processes as higher twist QCD contributions, taking into account spin and intrinsic transverse momentum effects in the quark…