Finite size effect on Dissociation and Diffusion of chiral partners in Nambu-Jona-Lasinio model

The masses of pion and sigma meson modes, along with their dissociation in the quark medium, provide detailed spectral structures of the chiral partners. One has seen collectivity in pA and pp systems both at LHC and RHIC. In this article, we study the restoration of chiral symmetry by investigating the finite size effect on the detailed structure of the chiral partners in the framework of the Nambu-Jona-Lasinio model. Their diffusions and conductions have been studied through this dissociation mechanism. It is found that the masses, widths, diffusion coefficients, conductivities of chiral partners merge at different temperatures in the restoration phase of chiral symmetry. However, merging points are shifted to lower temperatures when one introduces the finite size effect into the picture. The strengths of diffusions and conductions are also reduced once the finite size is introduced in the calculations.

Thermodynamic properties of light mesons and phase transition in an extended SU(2) NJL model

In this work, we study the temperature and chemical potential dependence of the masses of sigma and pion mesons as well as the quark condensate by using a SU(2) flavor version of the Nambu–Jona–Lassino model, introducing a prescription that mimics confinement. We have found that as the temperature increases, the mass of sigma shifts down, while the pion mass remains almost constant. On the other hand, the quark condensate decreases as the temperature and chemical potential increases. We have also analyzed the temperature and chemical potential dependence of the spectral function of the sigma meson, from which we observe at low values of T and [Formula: see text] an absence of a peak. Furthermore, as the Mott temperature is reached, its value increases abruptly and a distinct peak emerges, which is related with the dissociation of the sigma. For the case of [Formula: see text], the Mott dissociation is exhibited about the temperature of 189 MeV. We have also obtained the chiral phase diagram and the meson dissociation for different values of [Formula: see text]. From these results, we can state a relation between chiral symmetry restoration and Mott dissociation.

The sigma-meson exchange contribution to the muonic hydrogen Lamb shift

The sigma(ξ)meson exchange contribution to the potential of the muon-proton interactionin muonichydrogen inducedbythe ξ-meson coupling to two photons is estimated. The transition form factor ξ → γγ is deduced from the quark model and experimental data on the decay widths Γσγγ. It is shown that scalar meson exchange contribution to the Lamb shift in muonic hydrogen, △ELs(2P−2S ),is rather large and relevant for a comparison with coming precise experimental data.

The linear radial spectrum of scalar mesons from QCD sum rules in the planar limit

We discuss calculations of large-Nc masses of light scalar mesons from the QCD sum rules. Two methods based on the use of linear radial Regge trajectories are presented. We point out the appearance of state near 0.5 GeV in the scalar isoscalar channel which emerges in both methods and presumably corresponds to the lightest scalar particle - the sigma-meson.

The sigma meson from lattice QCD with two-pion interpolating operators

In this paper, we describe our studies of the sigma meson, [Formula: see text], using two-pion correlation functions. We use lattice quantum chromodynamics in the quenched approximation with so-called clover fermions. By working at unphysical pion masses we are able to identify a would-be resonance with mass less than [Formula: see text], and then extrapolate to the physical point. We include the most important annihilation diagram, which is “partially disconnected” or “single annihilation”. Because this diagram is quite expensive to compute, we introduce a somewhat novel technique for the computation of all-to-all diagrams, based on momentum sources and a truncation in momentum space. In practice, we use only [Formula: see text] modes, so the method reduces to wall sources. At the point where the mass of the pion takes its physical value, we find a resonance in the [Formula: see text] two-pion channel with a mass of approximately [Formula: see text] MeV, consistent with the expected properties of the sigma meson, given the approximations we are making.

QCD monopole and sigma meson coupling

Under the assumption of the Abelian dominance in QCD, we show that chiral condensate is locally present around a QCD monopole. The appearance of the chiral condensate around a GUT monopole was shown in the previous analysis of the Rubakov effect. We apply a similar analysis to the QCD monopole. It follows that the condensation of the monopole carrying the chiral condensate leads to the chiral symmetry breaking as well as quark confinement. To realize the result explicitly, we present a phenomenological linear sigma model coupled with the monopoles, in which the monopole condensation causes the chiral symmetry breaking as well as confinement. The monopoles are assumed to be described by a model of dual superconductor. Because the monopoles couple with mesons, we point out the presence of an observable color singlet monopole coupled with the mesons.