A unitarized nonrelativistic meson model which is successful for the description of the heavy and light vector and pseudoscalar mesons yields, in its extension to the scalar mesons but for the same model parameters, a complete nonet below 1 GeV. In the unitarization scheme, real and virtual meson-meson decay channels are coupled to the quark-antiquark confinement channels. The flavor-dependent harmonic-oscillator confining potential itself has bound states ǫ(1.3 GeV), S(1.5 GeV), δ(1.3 GeV), κ(1.4 GeV), similar to the results of other bound-state qq models. However, the full coupled-channel equations show poles at ǫ(0.5 GeV), S(0.99 GeV), δ(0.97 GeV), κ(0.73 GeV). Not only can these pole positions be calculated in our model, but also cross sections and phase shifts in the meson-scattering channels, which are in reasonable agreement with the available data for ππ, ηπ and Kπ in S-wave scattering.

The very recently observed D * sJ (2317) + meson is described as a quasi-bound scalar cs state in a unitarized meson model, owing its existence to the strong 3 P 0 OZI-allowed coupling to the nearby S-wave DK threshold. By the same mechanism, a scalar D * 0 (2100-2300) resonance is predicted above the Dπ threshold. These scalars are the charmed cousins of the light scalar nonet f 0 (600), f 0 (980), K * 0 (800), and a 0 (980), reproduced by the same model. The standard cn and cs charmed scalars D 0 and D s0

A potential model for mesons is presented, which combines quark confinement and strong decay in a realistic approach. The multichannel Schrodinger formalism is employed to describe a system of one or more permanently closed quark-antiquark channels in interaction with several two-meson channels. For the potential in the qQ channels a harmonic oscillator with constant frequency is taken. As for the meson channels only Okubo-Zweig-Iizuka-rule-allowed decays into two mesons of the pseudoscalar or vector type are considered. Final-state interactions between these mesons are not yet taken into account. The communication between confined and free channels is supposed to take place via the 3~o mechanism, for which a locally approximated transition potential is derived. In order to obtain an analytic solution for the S matrix, the transition potential is treated by using a multi-8-shell method. Kinematically relativistic corrections and color splitting allow a fairly successful treatment of pseudoscalar as well as vector mesons for all quark flavors. The results are confronted with the data and discussed.

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We argue that the low-lying scalar-meson nonet makes part of a subset of a family of infinitely many scalar-meson nonets, which in turn makes part of a family of infinitely many quark-antiquark bound states and resonances. We outline the properties of this subset.Comment: Talk presented at the workshop on "Scalar Mesons and Related Topics" honoring the 70th birthday of Michael Scadron, 11 pages, 7 figure