Related papers: Multichannel Description of Light and Intermediate…
I give a brief introduction to light $q\bar{q}$ resonances. The properties of $q\bar{q}$ states are discussed in the context of the constituent quark model, including predictions for mass and partial decay widths. Problems and puzzles in…
In this talk I briefly review the recent developments on light scalar meson spectroscopy, paying particular attention to the causes of major revision of the $\sigma$ or $f_0(500)$ meson in the Review of Particle Phsycis. This resonance,…
We evaluate lower bounds on the sum of the up and down quark masses. The bounds follow from the constraints provided by the dispersion relation obeyed by the two--point function of the scalar current density when combined with properties of…
Based on the largest event sample of diffractively produced $\pi^-\pi^-\pi^+$, obtained by a pion beam of $190~\rm{GeV/c}$ momentum, the COMPASS collaboration has performed the most advanced partial wave analysis on multi-body final states,…
Light scalar mesons are found to fit rather well a diquark-antidiquark description. The resulting nonet obeys mass formulae which respect, to a good extent, the OZI rule. OZI allowed strong decays are reasonably reproduced by a single…
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 present results for the spectrum of light and strange mesons on configurations with two flavors of mass-degenerate Chirally Improved sea quarks. The calculations are performed on seven ensembles of lattice size 16^3x32 at three different…
It is shown that the recent data on the $K^0_S K^+$ correlation in Pb-Pb interactions agree with the data on the $\gamma\gamma\to\eta\pi^0$ and $\phi\to\eta\pi^0\gamma$ reactions and support the four-quark model of the $a_0(980)$ meson. It…
A short review on light scalar mesons is performed both in experiment and theory. A naive model, constrained by D branching ratios, is derived in order to make predictions on the wave functions of the $f_0(600)$ and $a_0(980)$ mesons. This…
A theory of lepton decay constants based on the path-integral formalism is given for chiral and vector mesons. Decay constants of the pseudoscalar and vector mesons are calculated and compared to other existing results.
The partial width of the decay channels $f_0(500) \to \pi \pi$, $f_0(980) \to \pi \pi$ and $f_0(980) \to K \bar K$ are calculated using QCD light-cone sum rules method and a technique of the soft meson approximation. The scalar particles…
We investigate the implications of large N_c and chiral symmetry for the mass spectra of meson resonances. Unlike for most other mesons, the mass matrix of the light scalars deviates strongly from its large-N_c limit. We discuss the…
I review a proposed pattern of the light scalar mesons with q\bar{q} mesons and glueball above 1 GeV and tetraquark mesoniums below 1 GeV. Several challenges and caveats of calculating these light scalar mesons with dynamical fermions are…
Outline: 1. Introduction, 2. Confinement, chiral dynamics and light scalar mesons, 3. Chiral shielding of the \sigma(600), chiral constraints (the CGL band), the \sigma(600) and the f0(980) in \pi\pi->\pi\pi, \pi\pi->KKbar,…
Resonances appearing in hadronic scattering processes are described by a two-phase model. In the one phase, scattering products are observed, whereas the other phase describes confinement. A so-called ``Resonance-Spectrum Expansion'' is…
The $f_0$ mesons are studied in a combined analysis of data on the isoscalar S-wave processes $\pi\pi\to\pi\pi,K\overline{K},\eta\eta$ and on decays $J/\psi\to\phi(\pi\pi, K\overline{K})$, $\psi(2S)\to J/\psi(\pi\pi)$, and…
Outline: 1. Introduction, 2. Confinement, chiral dynamics and light scalar mesons, 3. Chiral shielding of \sigma(600), chiral constraints, \sigma(600), f_0(980) and their mixing in \pi\pi\to\pi\pi, \pi\pi\to K\bar K, and…
A separable potential model of three coupled channels (pion-pion, kaon-antikaon and an effective four pion) has been constructed and applied in the analysis of the isoscalar S-wave pion-pion and kaon-antikaon phase shifts and inelasticities…
The study of two-pseudoscalar and two-photon decays for the scalar meson nonet below 1 GeV is performed within an effective approach in which the scalar resonances are described as (Jaffe's) tetraquark states. The dominant (fall apart…
The decays of a light scalar meson into a vector meson and a photon ($S\to V\gamma)$ are evaluated in the tetraquark and quarkonium assignments of the scalar states. A link with the radiative decays $\phi\to S\gamma$ is established:…