Modification of the masses of the lightest neutral mesons in a hadronic medium under an external magnetic field

The effects of the Dirac sea of the nucleons are investigated within a covariant model of the hadronic interaction. I extend the usual Mean Field Approximation and present a procedure to deal with divergences which are proportional to polynomials on the magnetic field intensity. For this purpose a nucleon propagator is used which takes account of the full effect of the magnetic field as well as the presence of the anomalous magnetic moments of both protons and neutrons. I examine single-particle properties and bulk thermodynamical quantities and conclude that within a reasonable range of densities and magnetic intensities the effects found are moderate. energy approaches the QCD scale, i.e. qB ≈ (220M eV ) 2 [4, 5, 7, 10]. One of the features of the QHD models is the simplicity of conceptual resources and procedures. The crucial point for these models is the Mean Field Approximation (MFA) where the meson fields are replaced by their in medium-mean values. In addition, the bilinear products of fermion fields are replaced by their expectation values. In the last case the contributions coming from the Dirac sea of fermions are usually disregarded. The procedure is completed with the requirement of self-consistency of the scalar meson fields, which are not directly related to conserved charges. The same procedure was adopted for a model based on the chiral SU(3) symmetry of the strong interaction [18], which was used to study different aspects of hadronic matter subject to an external magnetic field [19,20,21]. Some attempts has been made to incorporate the vacuum contribution within this scheme [9,10]. However, in [9] the AMM of the nucleons are neglected, although very strong magnetic intensities are considered (q B ≈ (500M eV ) 2 ). Furthermore, there is no contribution of the neutron. On the other hand, in [10] a low magnetic intensity expansion is proposed for the nucleon propagator, where the discrete energy spectrum of the protons due to the Landau quantization is not taken into account. The technical difficulties arising when the vacuum contributions in the presence of an external magnetic field are included have recently been considered within the Nambu and Jona-Lasinio model of the quark interaction [16].An analysis of the magnitude of the vacuum effects under the influence of strong magnetic fields, taking into account all the physical ingredients in a coherent manner, is necessary to discuss the validity of the usual MFA. This is precisely the aim of the present work. Here a version of the QHD model with polynomial meson interactions is used; it is known as FSUGold [22]. Contributions of the vacuum are evaluated by using a nucleon propagator which includes the anomalous magnetic moments and the full interaction with the external magnetic field [23,24]. This propagator has been used to evaluate meson properties [20,24] and the effect of the AMM within the Nambu and Jona-Lasinio model [17]. Within this scheme I evaluate the effective nucleon mass and statistical properties such as the grand canonical potent...

Vacuum effects on the properties of nuclear matter under an external magnetic field

Aguirre

2019

D mesons in strongly magnetized asymmetric nuclear matter

Dhale

et al. 2018

The medium modifications of the open charm mesons (D andD) are studied in isospin asymmetric nuclear matter in the presence of strong magnetic fields, using a chiral effective model. The mass modifications of these mesons in the effective hadronic model, arise due to their interactions with the protons, neutrons and the scalar mesons (non-strange isoscalar σ, strange isoscalar, ζ and non-strange isovector, δ), in the magnetized nuclear matter. In the presence of magnetic field, for the charged baryon, i.e., the proton, the number density as well as the scalar density have contributions due to the summation over the Landau energy levels. For a given value of the baryon density, ρ B , and isospin asymmetry, the scalar fields are solved self consistently from their coupled equations of motion. The modifications of the masses of the D andD mesons are calculated from the medium modifications of the scalar fields and the nucleons. The effects of the anomalous magnetic moments of the nucleons on the masses of the open charm mesons are also investigated in the present work. The effects of isospin asymmetry as well as of the anomalous magnetic moments are observed to be prominent at high densities for large values of magnetic fields. * Electronic address: sushruth.

Open bottom mesons in asymmetric nuclear matter in the presence of strong magnetic fields

Dhale

et al. 2018

The modifications of the masses of the B andB mesons in asymmetric nuclear matter in the presence of strong magnetic fields, are investigated using a chiral effective model. The medium modifications of these open bottom mesons arise due to their interactions with the scalar mesons and the nucleons. In the magnetized nuclear matter, the proton has contributions from the Landau levels. In the chiral effective model, the masses of the B andB mesons are calculated from the leading term, namely the vectorial Weinberg Tomozawa term as well as from the next to leading order contributions, i.e., due to the scalar exchange and the range terms. Due to the Weinberg-Tomozawa term, theB mesons experience an attractive interaction in the symmetric nuclear matter, whereas the B mesons have a repulsive interaction. Inclusion of the contributions from the scalar exchange and the range terms as well, leads to drop of the masses of both B and B mesons. The effect of the isospin asymmetry breaks the mass degeneracy of the B + and B 0 (as well as of the B − andB 0 ) mesons, and its effect is observed to be large at high densities. The effects of anomalous magnetic moments of the nucleons are taken into account in the present study of the masses of the open bottom mesons in magnetized nuclear matter. * Electronic address: