Electroweak properties of baryons in a covariant chiral quark model (original) (raw)

Covariant electroweak nucleon form factors in a chiral constituent-quark model

The European Physical Journal A - Hadrons and Nuclei, 2002

Results for the proton and neutron electric and magnetic form factors as well as the nucleon axial and induced pseudoscalar form factors are presented for the chiral constituent quark model based on Goldstone-boson-exchange dynamics. The calculations are performed in a covariant framework using the point-form approach to relativistic quantum mechanics. The direct predictions of the model yield a remarkably consistent picture of the electroweak nucleon structure.

Covariant nucleon electromagnetic form factors from the Goldstone-boson-exchange quark model

Physics Letters B, 2001

We present a study of proton and neutron electromagnetic form factors for the recently proposed Goldstone-boson-exchange constituent quark model. Results for charge radii, magnetic moments, and electric as well as magnetic form factors are reported. The calculations are performed in a covariant framework using the point-form approach to relativistic quantum mechanics. All the predictions by the Goldstone-boson-exchange constituent quark model are found in remarkably good agreement with existing experimental data.

Relativistic study of nucleon electroweak properties in a constituent-quark model

The European Physical Journal A - Hadrons and Nuclei, 2003

We discuss the predictions of the Goldstone-boson-exchange constituent-quark model for the proton and neutron electric and magnetic form factors as well as the nucleon axial and induced pseudoscalar form factors. The results are calculated in a covariant framework using the point-form approach to relativistic quantum mechanics. The only input into the calculations is the nucleon wave function from the constituent-quark model. A remarkably consistent picture, with all aspects of the electroweak nucleon structure close to existing experimental data, is obtained.

Electroweak properties of the nucleon in a chiral constituent quark model

2002

Results for all elastic electroweak nucleon form factors are presented for the chiral constituent quark model based on Goldstone-boson-exchange dynamics. The calculations are performed in a covariant framework using the point-form approach to relativistic quantum mechanics. The direct predictions of the model yield a remarkably consistent picture of the electroweak nucleon structure.

Covariant axial form factor of the nucleon in a chiral constituent quark model

Physics Letters B, 2001

The axial form factor G A of the nucleon is investigated for the Goldstoneboson-exchange constituent quark model using the point-form approach to relativistic quantum mechanics. The results, being covariant, show large contributions from relativistic boost effects. The predictions are obtained directly from the quark-model wave functions, without any further input such as vertex or constituent-quark form factors, and fall remarkably close to the available experimental data.

Nucleon form factors in a covariant diquark-quark model

Nuclear Physics A, 1997

In a model where constituent quarks and diquarks interact through quark exchange the Bethe-Salpeter equation in ladder approximation for the nucleon is solved. Quark and diquark confinement is effectively parametrized by choosing appropriately modified propagators. The coupling to external currents is implemented via nontrivial vertex functions for quarks and diquarks to ensure gauge invariance at the constituent level. Nucleon matrix elements are evaluated in a generalised impulse approximation, and electromagnetic, pionic and axial form factors are calculated.

Nucleon electroweak form factors: Analysis of their spectral functions

Nuclear Physics A, 1996

We investigate the imaginary parts of the nucleon electromagnetic and axial form factors close to threshold in the framework of heavy baryon chiral perturbation theory. For the isovector electromagnetic form factors, we recover the well known strong enhancement near threshold. For the isoscalar ones, we show that there is no visible enhancement due to the three-pion continuum. This justifies the use of vector meson poles only in dispersion-theoretical calculations. We also calculate the imaginary part of the nucleon isovector axial form factor and show that it is small in the threshold region.

Current conservation in the covariant quark-diquark model of the nucleon

2000

The description of baryons as fully relativistic bound states of quark and glue reduces to an effective Bethe-Salpeter equation with quark-exchange interaction when irreducible 3-quark interactions are neglected and separable 2-quark (diquark) correlations are assumed. This covariant quark-diquark model of baryons is studied with the inclusion of the quark substructure of the diquark correlations. In order to maintain electromagnetic current conservation it is then necessary to go beyond the impulse approximation. A conserved current is obtained by including the coupling of the photon to the exchanged quark and direct "seagull" couplings to the diquark structure. Adopting a simple dynamical model of constituent quarks and exploring various parametrisations of scalar diquark correlations, the nucleon Bethe-Salpeter equation is solved and the proton and neutron electromagnetic form factors are calculated numerically. The resulting magnetic moments are still about 50% too small, the improvements necessary to remedy this are discussed. The results obtained in this framework provide an excellent description of the electric form factors (and charge radii) of the proton, up to a photon momentum transfer of 3.5GeV 2 , and the neutron.

Nucleon shape and electromagnetic form factors in the chiral constituent quark model

2010

The electromagnetic form factors are the most fundamental quantities to describe the internal structure of the nucleon and the shape of a spatially extended particle is determined by its intrinsic quadrupole moment which can be related to the charge radii. We have calculated the electromagnetic form factors, nucleon charge radii and the intrinsic quadrupole moment of the nucleon in the framework of chiral constituent quark model. The results obtained are comparable to the latest experimental studies and also show improvement over some theoretical interpretations.