Electromagnetic Properties Of Nucleons Research Articles

Electromagnetic properties of nucleons from lattice QCD

A numerical simulation of QCD on a quenched 24×12×12×24 lattice is used to calculate, at small momentum transfer, the electric and magnetic form factors of a variety of hadrons.

U(2)V Yang-Mills approach to Skyrmions with vector mesons: Electromagnetic properties of nucleons.

We investigate the electromagnetic properties of nucleons in an extended Skyrme model including the vector mesons rho and ..omega... We show that after collective quantization of the soliton in the presence of the vector mesons, the isovector charge is properly normalized. We calculate the electric form factor of the proton and the neutron which are in good and fair agreement with experiment, respectively. Finally, we discuss problems connected with the magnetic form factors in this minimal model. We argue that complete vector-meson dominance is not realized in low-energy hadron physics.

Constituent quark mass and nucleon properties in nuclei

It is shown that the Nolen-Schiffer anomaly, the quenching of gA and the increase in some electromagnetic properties of nucleons in nuclei can all be explained qualitatively in a constituent quark model if the quark mass is assumed to depend on its confinement size.

Experimental systematics of particle lifetimes and widths

By comparing the lifetimes of the metastable (τ>10−17 s) elementary particles with one another, we find experimentally that these lifetimes occur both as ratios of 2 and as ratios of α=e2/ħc, with supposedly dissimilar particles grouped together, and with no experimental counterexamples. When short-lived (τ ∼ 10−22 s) meson and baryon resonances are studied, it is found that the width is a key identification symbol. Grouping together resonances that have similar (narrow) widths, we obtain very accurate linear mass intervals. This mapping can be extended to include essentially all of the observed narrow-width meson and baryon resonances in a comprehensive pattern. These results suggest a weak-binding-energy approach to elementary-particle structure. This is the same conclusion that emerges from a broad overview of the successes of the quark model. The empirical level spacings point to the existence of two basic mass quanta, a spinless quantum μ ⋍ 70 MeV and a spin-1/2 quantumS ⋍ 330 MeV. Electromagnetic properties of nucleons also indicate the existence of the 330 MeV mass quantum. In reconciling a 330 MeV mass quantumS with a 939 MeV nucleon mass and a 1795 MeV\(\bar pn\) bound-state mass, we are led to the Fermi and Yang formulation of the nucleon rather than to the formulation of Gell-Mann and Zweig. The observed spectrum of narrow-width meson and baryon resonances can be reproduced by forming suitable combinations of the quanta μ andS. Broad-width resonances are interpreted as rotational excitations. Basis states 3 ≡ 3μ and 4 ≡ 4μ, initially selected to account for observed level spacings in hyperon resonances, are shown to have significance with respect to strangeness quantum numbers and with respect to basic characteristics of baryon and meson resonances. These basis states can also be used to account phenomenologically for the observed factors of 2 and α in the lifetimes of the metastable resonances. The predictive power of the present linear systematics is illustrated in a «meson excitation tower» for narrow-width resonances. First published in 1970, this excitation tower is shown with separate groupings for the resonances that were identified in 1970 and for the resonances that have subsequently been identified.

Sum rules for the mixing angles of the baryons in SU(3) ⊗ SU(3) chiral algebra at infinite momentum

Under the assumption that axial charges couple the baryon octet only to one-particle states belonging to 1, 8, 10 SU(3) representations, sum rules for the mixing angles of the baryon wave function are derived. The results obtained from their saturation are in good agreement with the known electromagnetic properties of nucleons.

Electromagnetic properties of nucleons and barion-heavy meson interactions

Electromagnetic properties of nucleons and barion-heavy meson interactions

Influence of "New Unstable Particles" on the Electromagnetic Properties of Nucleons

Influence of "New Unstable Particles" on the Electromagnetic Properties of Nucleons

Electromagnetic Properties of the Nucleon in a Finite Source Theory

Some electromagnetic properties of nucleons are investigated under the assumption that the nucleon consists of a spin one-half core particle in interaction with the pion field through a gauge-invariant, non-relativistic, pseudoscalar, finite source interaction. Recoil of the nucleon core is neglected and the weak coupling approximation is used. A method is presented for making the finite source interaction between two particle fields gauge-invariant by introducing filaments of current in the region of the source function. The theoretical contributions of interaction currents to the magnetic moments of the proton and neutron are calculated and found to be small compared to the observed anomalous moments and of the opposite sign. The model is used to calculate, in the limit of zero source size, the total and differential cross sections for scattering of gamma rays from nucleons. The results, which are presented graphically, are found to be in accord with the conditions imposed on a finite theory in the preceding paper. They are compared to the results obtained by Sachs and Foldy on the basis of a point-source theory.

The Electron-Neutron Interaction

The known electromagnetic properties of nucleons, assuming that the electron-neutron interaction is fundamentally of electromagnetic origin, are fitted into the phenomenological framework developed in the preceding paper and the results compared with predictions of weak coupling meson theories. The detailed comparison shows that the intrinsic electron-neutron interaction is somewhat smaller than predicted and it is suggested that even in the more favorable cases, the rough agreement as to order of magnitude may be largely due to a fortuitious cancellation of different contributions, which may easily be upset when higher order effects are included in the theory. Even apart from the detailed calculations, it is indicated that the observed intrinsic electron-neutron interaction is considerably smaller than order-of-magnitude expectations from general meson-theoretical principles. The results emphasize the importance of more accurate experimental determinations of the electron-neutron interaction, since a smaller value of the intrinsic interaction will either pose a very stringent test for any meson theory or require a critical re-evaluation of our present ideas regarding nucleonic structure. Some phenomena related to the electron-neutron interaction and the possibility that the intrinsic interaction may be nonelectromagnetic in origin are briefly discussed.

On the Electromagnetic Properties of Nucleons

The methods recently developed by Schwinger for dealing with problems in quantum electrodynamics have been applied to an investigation of the electromagnetic properties of nucleons in interaction with pseudoscalar mesons. The calculated values of the magnetic moments of the neutron and proton are in agreement with results previously obtained by Case, Luttinger, and Slotnick and Heitler using different calculational procedures. Our result for the neutron-electron interaction is identical with that obtained by Case. Included in this paper are the anomalous proton-electron interaction and a qualitative discussion of the scattering of high energy nucleons. The large coupling constants necessary to fit any of the experimental data show that the results obtained by a second order perturbation calculation are not quantitatively reliable.

On the Electromagnetic Properties of Nucleons, I

On the Electromagnetic Properties of Nucleons, I