Pion mass dependence of nucleon magnetic moments

Abstract

The relevance of the pion mass, provenient from a term which explicitely breaks chiral symmetry in the Lagrangian, for nucleon magnetic moment in the frame work of the Skyrme model in two different versions: the usual one model and a modified one which includes a coupling to a light scalar meson field, the sigma σ( 500 − 600 MeV). Results are compared to other calculations. Our main motivation comes from usual extrapolations for values of low energy QCD observables obtained in lattices with large values of pion/quark masses toward realistic value of m π which do not allow it. We do a comparison with results from the Cloudy Bag Model and a chiral hadronic model from chiral perturbation theory. There are several resulting extrapolations from the region of large pion mass to the realistic value depending on the considered model for low energy QCD.

Effect of the A-Term on the Nucleon Properties in the Extended Linear Sigma Model

“…During the last few years, there has been intense interest in various chiral quark models to the description of nucleon properties, such as the perturbative chiral quark model [9][10][11][12], extended Skyrme model [13,14] and extended linear sigma model [15][16][17]. The perturbative chiral quark model is an effective model of baryons based on chiral symmetry.…”

“…[9][10][11][12]). The original Skyrme model Lagrangian consists of the non-linear sigma model term and the fourth-order derivative term, which guarantees the stabilization of the soliton so that the degree of freedom of the sigma field may be replaced by a variable chiral radius, which becomes the new dynamic degree of freedom that plays an important role in the modified Skyrmion Lagrangian density, in which the dependence of the observables on the values of the scalar meson mass and on the fourth-order coupling term e were also considered [13,14]. On the other hand, Broniowski and Golli [15] analyzed a particular extension of the linear sigma model coupled to valence quarks, which contained an additional term with gradients of the chiral fields and investigated the dynamic consequence of this term and its relevance to the phenomenology of the soliton models of the nucleon.…”