18 research outputs found
Electromagnetic form factors of the baryon octet in the perturbative chiral quark model
We apply the perturbative chiral quark model at one loop to analyze the
electromagnetic form factors of the baryon octet. The analytic expressions for
baryon form factors, which are given in terms of fundamental parameters of
low-energy pion-nucleon physics (weak pion decay constant, axial nucleon
coupling, strong pion-nucleon form factor), and the numerical results for
baryon magnetic moments, charge and magnetic radii are presented. Our results
are in good agreement with experimental data.Comment: 15 pages, 6 figures, to be published in Eur. Phys. J.
Axial form factor of the nucleon in the perturbative chiral quark model
We apply the perturbative chiral quark model (PCQM) at one loop to analyze
the axial form factor of the nucleon. This chiral quark model is based on an
effective Lagrangian, where baryons are described by relativistic valence
quarks and a perturbative cloud of Goldstone bosons as dictated by chiral
symmetry. We apply the formalism to obtain analytical expressions for the axial
form factor of the nucleon, which is given in terms of fundamental parameters
of low-energy pion-nucleon physics (weak pion decay constant, strong
pion-nucleon form factor) and of only one model parameter (radius of the
nucleonic three-quark core).Comment: 23 pages, 5 figures, accepted for publication in J. Phys.
Light baryon magnetic moments and N -> Delta gamma transition in a Lorentz covariant chiral quark approach
We calculate magnetic moments of light baryons and N -> Delta gamma
transition characteristics using a manifestly Lorentz covariant chiral quark
approach for the study of baryons as bound states of constituent quarks dressed
by a cloud of pseudoscalar mesons.Comment: 29 pages, 10 figures, accepted for publication in Phys. Rev.
The neutron electric dipole form factor in the perturbative chiral quark model
We calculate the electric dipole form factor of the neutron in a perturbative
chiral quark model, parameterizing CP-violation of generic origin by means of
effective electric dipole moments of the constituent quarks and their
CP-violating couplings to the chiral fields. We discuss the relation of these
effective parameters to more fundamental ones such as the intrinsic electric
and chromoelectric dipole moments of quarks and the Weinberg parameter. From
the existing experimental upper limits on the neutron EDM we derive constraints
on these CP-violating parameters.Comment: 20 pages, 3 figure
Nucleon polarizabilities in the perturbative chiral quark model
The nucleon polarizabilities alpha(E) and beta(M) are studied in the context
of the perturbative chiral quark model. We demonstrate that meson cloud effects
are sufficient to explain the electric polarizability of nucleon. Contributions
of excite quark states to the paramagnetic polarizability are dominant and
cancel the diamagnetic polarizability arising from the chiral field. The
obtained results are compared to data and other theoretical predictions.Comment: 25 pages, 18 figures, 2 table
Electromagnetic nucleon-delta transition in the perturbative chiral quark model
We apply the perturbative chiral quark model to the gamma N -> Delta
transition. The four momentum dependence of the respective transverse helicity
amplitudes A(1/2) and A(3/2) is determined at one loop in the pseudoscalar
Goldstone boson fluctuations. Inclusion of excited states in the quark
propagator is shown to result in a reasonable description of the experimental
values for the helicity amplitudes at the real photon point.Comment: 25 page
Dependence of nucleon properties on pseudoscalar meson masses
We discuss the sensitivity of nucleon properties (mass, magnetic moments and
electromagnetic form factors) on the variation of the pseudoscalar meson masses
in the context of the perturbative chiral quark model. The obtained results are
compared to data and other theoretical predictions.Comment: 18 pages, 12 figures, accepted for publication in J. Phys.
Strong CP violation and the neutron electric dipole form factor
We calculate the neutron electric dipole form factor induced by the CP
violating theta-term of QCD, within a perturbative chiral quark model which
includes pion and kaon clouds. On this basis we derive the neutron electric
dipole moment and the electron-neutron Schiff moment. From the existing
experimental upper limits on the neutron electric dipole moment we extract
constraints on the theta-parameter and compare our results with other
approaches.Comment: 18 pages, 2 figures, accepted for publication in Phys. Atom. Nuc