Related papers: Possible Classification of the Chiral Scalar sigma…
Underlying mixing of scalar mesons is studied in $\eta'\rightarrow \eta\pi\pi$ decay within a generalized linear sigma model of low-energy QCD which contains two nonets of scalar mesons and two nonets of pseudoscalar mesons (a…
Based on the recently proposed Roy-Steiner equations for pion-nucleon scattering, we derive a system of coupled integral equations for the pi pi --> N-bar N and K-bar K --> N-bar N S-waves. These equations take the form of a two-channel…
First I review some previous work on the lightest scalars below 1.5 GeV, and how these scalars can be understood as unitarized nonet states. The bare scalars are strongly distorted by hadronic mass shifts, and the lightest I=0 state becomes…
Within a linear sigma model framework, possible mixing between two chiral nonets (a two quark nonet, and a four quark nonet) below 2 GeV is studied. Incorporating the U(1)$_A$ behavior of the underlying QCD, and working in the isospin…
We first review the work of the Syracuse group, which uses an effective chiral Lagrangian approach, on meson-meson scattering. An illustration providing evidence for the existence of a strange scalar resonance of mass around 900 MeV is…
The highlights of studies of mixing among scalar mesons below and above 1 GeV within a nonlinear chiral Lagrangian framework is briefly presented. Two scalar meson nonets are introduced to explore the mass spectrum and decay properties of…
We consider mixing of the antidecuplet with three J^P=1/2^+ octets (the ground-state octet, the octet containing N(1440), \Lambda(1600), \Sigma(1660) and \Xi(1690) and the octet containing N(1710), \Lambda(1800), \Sigma(1880) and \Xi(1950))…
We show that the application of Regge phenomenology to SU(4) meson multiplets leads to a new Gell-Mann-Okubo mass-mixing formula in the SU(3) sector, 3m_1^2 + (cos theta)^2 m_0^2 + (sin theta)^2 m_{0'}^2 + sqrt{2} sin(2theta) (m_0^2 -…
Our method of analysis, which led to existence of sigma and kappa mesons, is reviewed and examined from a viewpoint of general S-matrix. It is shown that the method is consistent with the constraints from chiral symmetry and unitarity.…
We enforce chiral Ward identities on the vertices of the linear sigma model to take into account the width of the scalar sigma, considered as a true physical resonance. We consider pion scattering at very low energies and, from a fit to the…
We study the feasibility of having the $\Sigma^*(1430)$ state, predicted within the chiral unitary approach and recently reported by the Belle Collaboration, as corresponding to a state of non-molecular nature. Starting from this…
The radiative $\phi\to\pi^0\eta\gamma$ decay is discussed emphasizing the effects of the $a_0$(980) scalar resonance which dominates the high values of the $\pi^0\eta$ invariant mass spectrum. In its lowest part, the proposed amplitude…
Scalar-isoscalar mesons are studied using an unitary model in three channels: pi-pi, K-anti K and an effective 2pi-2pi. All the solutions, fitted to the pi-pi and K-anti K data, exhibit a wide f0(500), a narrow f0(980) and two relatively…
We present that there should exist a light strange-scalar meson kappa', in addition to the kappa(800), which has a mass around 1.1-1.2 GeV, a rather narrow width, and couples strongly to kappa(800)sigma(600) (Kpipipi) but weakly to Kpi,…
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…
The complementarity between Chiral Perturbation Theory and the Linear Sigma Model in the scalar channel is exploited to study $\pi^0\pi^0$ production in $\rho$ and $\omega$ radiative decays, where the effects of a low mass scalar resonance…
We investigate the $a_0(980)$ resonance within chiral effective field theory through a three-coupled-channel analysis, namely $\pi\eta$, $K\bar{K}$ and $\pi\eta'$. A global fit to recent lattice finite-volume energy levels from $\pi\eta$…
A consistent description of the pi0 pi0 invariant mass distribution in the phi(1020) -> f0(980) gamma -> pi0 pi0 gamma decay and the pi0 eta in phi(1020) -> a0(980) gamma -> pi0 eta gamma is suggested. A search for the consequences of the…
In the I=0 sector there are more scalar mesons than can fit in one $q{\bar q}$ nonet. Consequently, many have claimed that there is in fact more than one multiplet, perhaps both $q{\bar q}$ and $qq{\bar {qq}}$. Such proposals require the…
A novel, nonperturbative, way to generate chiral symmetry breaking within the linear sigma model for 3 flavours is discussed. After spontaneous chiral symmetry breaking in the vacuum at the tree level the scalar nonet obtains mass, while…