Related papers: How can one understand the lightest scalars, espec…
The formulae needed to parametrise sigma, kappa, a0(980) and f0(980) are reviewed. For sigma and kappa, the Adler zero due to Chiral Symmetry Breaking plays a crucial role. The f0(980) and a0(980) are locked to the KK threshold by a cusp…
Within the context of a generalized linear sigma model that includes two nonets of scalar mesons (a two-quark nonet and a four-quark nonet) and two nonets of pseudoscalar mesons (a two-quark nonet and a four-quark nonet) a collective…
As an interpretation of the 750 GeV diphoton excesses recently reported by both ATLAS and CMS collaborations, we consider a simple extension of the Standard Model with a Dirac fermion dark matter where a singlet complex scalar field…
We investigate the isospin-violating mixing of the light scalar mesons a0(980) and f0(980) within the unitarized chiral approach. Isospin-violating effects are considered to leading order in the quark mass differences and electromagnetism.…
We consider mesons composed of light and heavy quarks and discuss the construction of the corresponding meson wave functions in soft-wall AdS/QCD. We specifically take care that constraints imposed by chiral symmetry breaking and by the…
The $s-$wave meson-baryon scattering is analyzed for the isospin-strangeness $I=1/2, S=0$ and $I=0,S=-1$ sectors, in a Bethe-Salpeter coupled channel formalism incorporating Chiral Symmetry. For both sectors, four channels have been…
A coupled channel model is used to study the nature of the f0(980) resonance. It is shown that the existence of two poles close to KKbar threshold, as found in many data fits and confirmed here, can be reconciled with the KKbar molecular…
After a brief summary of the QCD phase structure with light quarks, we discuss two recent developments on in-medium hadrons. First topic is the sigma-meson which is a fluctuation of the chiral order parameter \bar{q}q. Although sigma is at…
We study basic properties of scalar hadronic resonances within a quantum field theoretical toy model. In particular, we focus on the spectral function, the mass and the decay width of the resonance $f_{0}(500)$. In this work, this meson is…
We develop a scheme for the extraction of the properties of the scalar mesons $f_0(600)$, $f_0(980)$, and $a_0(980)$ from lattice QCD data. This scheme is based on a two-channel chiral unitary approach with fully relativistic propagators in…
In the SU(3) symmetry limit, the ratio $R\equiv\frac{{\cal B}(D^+\to f_0l^+\nu)+ {\cal B}(D^+\to \sigma l^+\nu)}{{\cal B}(D^+\to a_0^0l^+\nu)}$ is equal to 1 if the scalar mesons are $\bar qq$ states, while it is 3 if these mesons are…
We review our recent dispersive and model independent determination of the lightest two scalars, in terms of poles and residues - or mass, width and coupling- by means of once and twice subtracted Roy equations, using as input constrained…
We study the structure of the $\Lambda_c(2595)$ and $\Lambda_c(2625)$ resonances in the framework of an effective field theory consistent with heavy quark spin and chiral symmetries, that incorporates the interplay between…
It is presented a critical consideration of all unusual properties of the scalar $a_0(980)$ and $f_0(980)$-mesons in the four-quark, two-quark and molecular models. The arguments are adduced that the four-quark model is more preferable. It…
This talk is a brief account of recent developments on light scalar meson spectroscopy. I mostly focus on the major revision of the $\sigma$ or $f_0(500)$ meson in the Review of Particle Physics, driven by new data and the accummulation of…
The scalar mesons $\sigma(600)$, $\kappa(800)$, $f_0(980)$ and $a_0(980)$ together with the pseudo Goldstone bosons $\pi$, $K$, and $\eta$ may be considered as the Higgs sector of strong interaction. After a long time of uncertainty about…
The $S$-wave $\Lambda K$ and $\Sigma K$ states with isospin $I=1/2$ are dynamically investigated within the framework of the chiral SU(3) quark model by solving a resonating group method (RGM) equation. The model parameters are taken from…
We study the mass, width and couplings of the lightest resonance multiplet with I(J^{PC})=1(1^{--}) quantum numbers. Effective field theories based on chiral symmetry are employed in order to describe the form factor associated with the…
We calculate low-energy meson decay processes and pion-pion scattering lengths in a two-flavour linear sigma model with global chiral symmetry, exploring the scenario in which the scalar mesons $f_0$(600) and $a_0$(980) are assumed to be…
We first discuss the theoretical and phenomenological significance of the sigma meson ($\sigma$) in QCD. It is indicated that if the collective modes with the mass 500-600 MeV exists in the $I=J=0$ channel, various empirical facts in hadron…