Related papers: Problem of Light Scalar Mesons
In this paper the spectrum of quark-antiquark systems, including light mesons and tachyons, is studied in the true vacuum and in the chiral invariant vacuum. The mass gap equation for the vacua and the Salpeter-RPA equation for the mesons…
Charmed scalar mesons are studied. By assigning the newly observed charmed strange meson with a narrow width to one of the iso-triplet four-quark mesons, decays of the multiplet members are investigated and, as the consequence, existence of…
Weak decays of charm mesons has been used for studies of light quark spectroscopy, with particular emphasis on the J^{PC}=0^{++} states. Recent results on light scalars are summarized and some conceptual issues are discussed, especially the…
We study the properties of the lowest multiplet of light-flavor tensor meson resonances, i.e. $f_2(1270)$, $a_2(1320)$, $K_2^*(1430)$, and $f_2'(1525)$, within the resonance chiral theory approach. The higher-order resonance chiral…
We study pi eta scattering in a model which starts from the tree diagrams of a non-linear chiral Lagrangian including appropriate resonances. Previously, models of this type were applied to pi pi and pi K scattering and were seen to require…
In the light scalar meson sector (M < 1.8 GeV) one expects at least one q qbar nonet and a glueball, possibly also multi-quark states. We discuss the present phenomenological evidence for sigma and kappa particles; if real, they could be…
We work out the Linear Sigma Model (LSM) predictions for the 2 gamma decay rates of the a_0(980),f_0(980) mesons under the assumption that they are respectively the I=1 and I=0 members of the bar q q scalar nonet. Agreement with…
We consider the contribution of scalar resonances to hadronic light-by-light scattering in the anomalous magnetic moment of the muon. While the $f_0(500)$ has already been addressed in previous work using dispersion relations, heavier…
Electromagnetic decays of the scalar mesons are shown to be constrained by chiral symmetry as a consequence of the fact that, in the chiral limit, the two and three-point functions $<SS-PP>$ and $<VVS>$ satisfy super-convergent dispersion…
We consider chiral perturbation theory with an explicit broad $\sigma$-meson and study its contribution to the scalar form factors of the pion and the nucleon. Our goal is to learn more about resonance saturation in the scalar sector.
We discuss the classification of the light scalar mesons with mass below 2 GeV into q qbar nonets and glueballs. The information on production and decay of these states, in particular recent information on f_0(980), f_0(400-1200) (or…
Two-photon decays of light scalar mesons are discussed within the quarkonium and tetraquark asignements: in both cases the decay rate of the sigma resonances turns out to be smaller than 1 keV.
The light scalar meson spectrum is studied using the improved ladder QCD with the UA(1) breaking Kobayashi-Maskawa-'t Hooft interaction by solving the Schwinger-Dyson and Bethe-Salpeter equations. The dynamically generated…
In this talk, an overview of the status of the light scalar mesons in the context of the non linear chiral Lagrangian of references [1-3] is presented. The evidence for the existence of a scalar nonet below 1 GeV is reviewed, and it is…
The surprising thing is that arising almost 50 years ago from the linear sigma model (LSM) with spontaneously broken chiral symmetry, the light scalar meson problem has become central in the nonperturbative quantum chromodynamics (QCD) for…
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…
We study light scalar mesons in the AdS/QCD soft-wall model with a background dilaton field, to investigate the features of this approach in describing QCD properties in the strong coupling regime. We find that the masses and decay…
In this review I discuss the role of chiral extrapolations for the determination of several phenomenologically relevant quantities, including light quark masses, meson decay constants and the axial charge of the nucleon. In particular, I…
Despite the apparent simplicity of meson spectroscopy, light scalar mesons cannot be accommodated in the usual $q\bar q$ structure. We study the description of the scalar mesons below 2 GeV in terms of the mixing of a chiral nonet of…
We study pseudoscalar and scalar mesons using a practical and symmetry preserving truncation of QCD's Dyson-Schwinger equations. We investigate and compare properties of ground and radially excited meson states. In addition to exact results…