Relativistic study of nucleon electroweak properties in a constituent-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.

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 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.

Electroweak properties of baryons in a covariant chiral quark model

2001

The proton and neutron electromagnetic form factors and the nucleon axial form factor have been calculated in the Goldstone-boson exchange constituent-quark model within the point-form approach to relativistic quantum mechanics. The results, obtained without any adjustable parameter nor quark form factors, are, due to the dramatic effects of the boost required by the covariant treatment, in striking agreement with the data.

Nucleon electromagnetic and axial form factors in point-form relativistic quantum mechanics

2002

Results for the proton and neutron electric and magnetic form factors as well as the nucleon axial form factor are presented for constituent quark models, based on either one-gluon-exchange and Goldstone-boson-exchange dynamics. The calculations are performed in a covariant framework using the point-form approach to relativistic quantum mechanics. The only input to the calculations is the nucleon wave function of the corresponding constituent quark model. A comparison is given to results of the instanton-induced constituent quark model treated with the Bethe-Salpeter equation.

Relativistic quark spin coupling effects in the correlations between nucleon electroweak properties

Nuclear Physics A, 2001

We investigate the effect of different relativistic spin couplings of constituent quarks on nucleon electroweak properties. Within each quark spin coupling scheme the correlations between static electroweak observables are found to be independent of the particular shape of the momentum part of the nucleon light-front wave function. The neutron charge form factor is very sensitive to different choices of spin coupling schemes once the magnetic moment is fitted to the experimental value. However, it is found rather insensitive to the details of the momentum part of the three-quark wave function model.

Nucleon electromagnetic form factors in a relativistic quark-pair-creation model

Nuclear Physics A, 2001

We study the effects of the |qqq qq component of the hadronic wave function on the description of the electromagnetic structure of the nucleon. Starting with a 3q baryonic wave function which describes the baryonic and mesonic low energy spectrum, the extra qq pair is generated through a relativistic version of the 3 P 0 model. It is shown that this model leads to a renormalization of the quark mass that allows one to construct a conserved electromagnetic current. We conclude that these dynamical relativistic corrections play an important role in reproducing the Q 2 dependence of the electromagnetic form factors at low Q 2 .

A relativistic study of the nucleon form factors

European Physical Journal A

We perform a calculation of the relativistic corrections to the electromagnetic elastic form factors of the nucleon obtained with various Constituent Quark Models. With respect to the non relativistic calculations a substantial improvement is obtained up to Q 2 ≃ 2(GeV /c) 2 .

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 properties in the covariant quark-diquark model

The European Physical Journal A, 2000

In the covariant quark-diquark model the effective Bethe-Salpeter (BS) equations for the nucleon and the ∆ are solved including scalar and axialvector diquark correlations. Their quark substructure is effectively taken into account in both, the interaction kernel of the BS equations and the currents employed to calculate nucleon observables. Electromagnetic current conservation is maintained. The electric form factors of proton and neutron match the data. Their magnetic moments improve considerably by including axialvector diquarks and photon induced scalar-axialvector transitions. The isoscalar magnetic moment can be reproduced, the isovector contribution is about 15% too small. The ratio µ GE/GM and the axial and strong couplings gA, gπNN , provide an upper bound on the relative importance of axialvector diquarks confirming that scalar diquarks nevertheless describe the dominant 2-quark correlations inside nucleons. PACS. 11.10.St (Bound states; Bethe-Salpeter equations) -12.39.Ki (Relativistic quark model) -12.40.Yx (Hadron mass models and calculations) -13.40.Em (Electric and magnetic moments) -13.40.Gp (Electromagnetic form factors) -13.75.Gx (Pion-baryon interactions) -14.20.Dh (Protons and neutrons)