How we discovered the nonet of light scalar mesons

TL;DR

This paper discusses the discovery and theoretical prediction of a nonet of light scalar mesons, confirming their existence through lattice QCD and experimental data, and exploring their role within the meson spectrum.

Contribution

The paper introduces a model related to the RSE that predicts a complete nonet of light scalar mesons, integrating them into the ordinary meson spectrum and confirming their presence through recent experimental analyses.

Findings

Confirmation of light scalar meson poles in experimental data

Prediction of a nonet of light scalar mesons within the meson spectrum

Identification of these mesons as part of the ordinary meson spectrum

Abstract

As has been confirmed meanwhile by lattice-QCD calculations (see e.g. hep-lat/0702023), the confinement spectrum of non-exotic quark-antiquark systems has its ground state for scalar mesons well above 1 GeV in the Resonance Spectrum Expansion (RSE). For instance, in the S-wave Kaon-pion RSE amplitude, a broad resonance was predicted slightly above 1.4 GeV [hep-ex/0106077], which is confirmed by experiment as the K*0(1430). However, a complete nonet of light scalar mesons was predicted (Zeit.Phys.C30,615 [http://www-spires.slac.stanford.edu/spires/find/hep?key=1573454]) as well, when a model strongly related to the RSE and initially developed to describe the heavy quarkonia resonance spectra (Phys.Rev.D21,772 [http://www-spires.slac.stanford.edu/spires/find/hep?key=363162]) was applied in the light-quark sector. Thus, it was found that the light scalar-meson nonet constitutes part of the ordinary meson spectrum, albeit represented by "extraordinary" [hep-ph/0701038] poles [hep-ex/0106077]. Similar resonances and bound states appear in the charmed sector [hep-ph/0305035], and are predicted in the B-meson spectrum [hep-ph/0312078, hep-ph/0406242]. A recent work [hep-ph/0703286] confirmed the presence of light scalar-meson poles in the RSE amplitude for S-wave and P-wave pion-pion and Kaon-pion contributions to three-body decay processes measured by the BES, E791 and FOCUS collaborations.