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Data on the form factors for K decay make it possible to fix the value of a parameter that is not determined by the theory itself and which is contained in the Lagrangian for the system formed by 0 and 0 mesons. This makes it possible to find the mass of the lightest σ meson: mσ = 663 MeV. As for the nature of spin-1 mesons, which also contribute to the form factors for K decay, data on them give no way to interpret spin-1 mesons as gauge bosons of chiral theory [ABSTRACT FROM AUTHOR]

Abstract: The is a flavor partner of the meson which contains the strange quark. Because of the quasi-bound state which lies below the threshold, the interaction of the and the nucleon is considered to be strongly attractive, leading to the possibility of the bound nuclei. On the other hand, the is the Nambu–Goldstone boson of spontaneous breaking of chiral SU(3)×SU(3) symmetry in QCD. We discuss the dynamics of the interaction and the systems from the viewpoint of chiral symmetry. [ABSTRACT FROM AUTHOR]

We calculate the S -wave scattering lengths for charmed mesons scattering off Goldstone bosons and explore their quark mass dependence using the chiral perturbation theory up to next-to-leading order as well as a unitarized version of it. The quark mass dependence of all scattering lengths determined in a recent lattice calculation can be reproduced by the unitarized version. We also discuss signals of possible bound states in these observables. [ABSTRACT FROM AUTHOR]

By describing within the chiral unitary approach the s -wave interaction of the vector meson nonet with the octet of pseudoscalar Goldstone bosons, we find that the main component of the axial-vector mesons -- b1(1235) , h1(1170) , h1(1380) , a1(1260) , f1(1285) and the two states associated to the K1(1270) -- does not follow the QCD dependence on the number of colors for ordinary q $ \bar{{q}}$ mesons. [ABSTRACT FROM AUTHOR]

The chiral effective Lagrangian for pseudoscalar meson nonet including eight Goldstone bosons and a SU(3) singlet η0 is constructed with the breaking effect of chiral symmetry in both quark condensate and quark mass differences taken into account. The $\tilde{\pi}^0-\eta-\eta^\prime$ mixing is discussed. By solving the mass equations of pseudoscalar mesons, the quark mass ratios are obtained and the quark condensate ratios are constrained in ranges. The mass split of π0-π± is discussed. [ABSTRACT FROM AUTHOR]

In the framework of the Nambu-Jona-Lasinio model with two quark flavors, we investigate the spectrum of meson and diquark excitations of dense quark matter in the phase with color superconductivity. The color SUc(3) symmetry is spontaneously broken to SUc(2) in this phase. But instead of the expected five Goldstone bosons in the mass spectrum, we observe only three, among which two bosons obey the quadratic dispersion law. We find the doublet of light diquark states with the mass ∼ 15 MeV and also the heavy diquark resonance (SUc(2) singlet) with the mass ∼ 1100 MeV. The π-and σ-mesons have the mass ∼ 330 Mev in the phase with color superconductivity. The π-mesons are then stable particles, while the σ-meson is stable only in the chiral limit in which the current quark mass m0 becomes zero. If m0 ≠ 0, then the σ-meson mixes with diquarks in the phase with color superconductivity and becomes a resonance with the width ∼ 30 MeV. [ABSTRACT FROM AUTHOR]

The chiral symmetry is applied to an extended constituent quark potential model. With random phase approximation (RPA), a small component effect is added to the constituent quark model. To obtain the pseudoscalar π meson as a Goldstone boson, the quark effective potentials are modified in the model to account for the dynamical breaking of chiral symmetry. Also the vector ρ meson is calculated and the KSRF relation about π and ρ meson decay constants is derived in the model. [Copyright &y& Elsevier]