Related papers: Axial Anomaly and the Nucleon Spin
We calculate the nucleon parameters in isospin symmetric and asymmetric nuclear matter using the QCD sum rules. The higher moments of the nucleon structure functions are included. The complete set of the nucleon expectation values of the…
It is argued that the constituent quarks are expected to show a non-- trivial spin and flavor structure, due to the anomalous breaking of the chiral symmetry in the U(1) sector. CERN--TH.7079/93\\
We have measured the neutron spin asymmetry $A_1^n$ with high precision at three kinematics in the deep inelastic region at $x=0.33$, 0.47 and 0.60, and $Q^2=2.7$, 3.5 and 4.8 (GeV/c)$^2$, respectively. Our results unambiguously show, for…
We determine within lattice QCD, the nucleon spin carried by valence and sea quarks, and gluons. The calculation is performed using an ensemble of gauge configurations with two degenerate light quarks with mass fixed to approximately…
Removal of the quenched approximation in the mechanism which produced an analytic estimate of quark-binding potentials, along with a reasonable conjecture of the color structure of the nucleon formed by such a binding potential, is shown to…
We present a lattice calculation of the leading corrections to the masses of nucleons and $\Delta$ resonances. These are obtained in QCD+QED at $1$st order in the Isospin Breaking parameters $\alpha_{EM}$, the electromagnetic coupling, and…
In analogy to the Altarelli-Parisi equation for the quark and gluon helicity contributions to the nucleon spin, we derive an evolution equation for the quark and gluon orbital angular momenta. The solution of the combined equations yields…
The quark condensate in nuclear matter contains a term of order $\rho m_\pi$, arising from the contribution of low-momentum virtual pions to the $\pi N$ sigma commutator. Standard treatments of QCD sum rules for a nucleon in matter generate…
$\pi$-$N$ $\sigma$ term and proton axial vector matrix elements are calculated including disconnected contributions with a variant wall source method using the Wilson quark action at $\beta=5.7$ in quenched QCD. For the $\sigma$ term, we…
Based on a previous study of deriving the chiral Lagrangian (CL) from QCD, we illustrate the main feature of QCD predictions for the CL coefficients (CLC) in certain approximations. We first show that, in the large-N(c) limit, the anomaly…
C o n t e n t s 1. Introduction. 2. General Relations. 3. Small $x$ Domain -- Regge Behaviour. 4. The Parton Model. 5. Sum Rules in the Parton Model. 6. QCD Corrections to Sum Rules. 7. Nucleon Axial Coupling Constants. 8. The Experimental…
The proton spin problem triggered by the EMC experiment and its present status are closely examined. Recent experimental and theoretical progresses and their implications are reviewed. It is pointed out that the sign of the sea-quark…
{}From the deep-inelastic momentum sum rule and the trace anomaly of the energy-momentum tensor, I derive a separation of the nucleon mass into the contributions of the quark and gluon kinetic and potential energies, the quark masses, and…
We revisit the scale evolution of the quark and gluon spin contributions to the proton spin, $\frac{1}{2}\Delta \Sigma$ and $\Delta G$, using the three-loop results for the spin-dependent evolution kernels available in the literature. We…
We report results of our calculation on the $\pi N\sigma$ term and quark spin content of the nucleon on the quenched $16^3 \times 24$ lattice at $\beta = 6.0$. The disconnected insertions which involve contributions from the sea quarks are…
The part of the proton spin $\Sigma$ carried by $u, d, s$ quarks is calculated in the framework of the QCD sum rules in the external fields. The operators up to dimension 9 are accounted. An important contribution comes from the operator of…
We review the state of our knowledge concerning the contribution of strange quarks to various nucleon properties. In the case of the electric and magnetic form factors, the level of agreement between theory and experiment is very…
A review of the calculations of the proton's spin using lattice QCD is presented. Results for the three contributions, the quark contribution $\sum_{q=u,d,s,c} (\frac{1}{2} {\Delta q})$, the total angular momentum of the quarks $J_q$ and of…
It is shown that in both the gluonic and strange sea explanations of the Ellis-Jaffe sum rule violation discovered by the European Muon Collaboration (EMC), the spin of the proton, when viewed in in its rest reference frame, could by fully…
The chiral quark model with a nonet of Goldstone bosons can yield an adequate description of the observed proton flavor and spin structure. In a previous publication we have compared the results of a SU(3) symmetric calculation with the…