Hanhart, ChristophKubis, BastianPeláez Sagredo, José Ramón2023-06-202023-06-202007-101550-799810.1103/PhysRevD.76.074028https://hdl.handle.net/20.500.14352/51719©2007 The American Physical Society. We wish to thank Timo Lähde for very helpful communications and Email exchanges, and, in particular, for making preliminary fit results and numbers on the threechannel generalization of Ref. [24] available to us. B. K. and J. R. P. are grateful for the hospitality of the Institut für Kernphysik at the Forschungszentrum Jülich in the initial stage, and B. K. for that of the Facultad de Ciencias Físicas at the Universidad Complutense Madrid in the final stage of this project. The authors acknowledge partial financial support by the EU I3HP Project (RII3-CT-2004-506078). B. K. was supported by the DFG (SFB/TR 16). The research of J. R. P. was partially funded by Spanish CICYT Contracts No. FPA2005-02327 and No. FIS2006-03438, as well as Banco Santander/Complutense Contract No. PR27/ 05-13955-BSCH.We investigate the isospin-violating mixing of the light scalar mesons a_0(980) and f_0(980) within the unitarized chiral approach. Isospin-violating effects are considered to leading order in the quark mass differences and electromagnetism. In this approach both mesons are generated through meson-meson dynamics. Our results provide a description of the mixing phenomenon within a framework consistent with chiral symmetry and unitarity, where these resonances are not predominantly qq̅ states. Amongst the possible experimental signals, we discuss observable consequences for the reaction J/ ψ→Øπ^0 ɳ in detail. In particular, we demonstrate that he effect of a_(0) –f_(0) mixing is by far the most important isospinbreaking effect in the resonance region and can indeed be extracted from experiment.engjournal articlehttp://dx.doi.org/10.1103/PhysRevD.76.074028http://journals.aps.orgopen access51-73Chiral perturbation-theoryPion-kaon scatteringScalar mesonsIsospin violationElastic-scatteringMultiquark hadronsRadiative decaysVirtual photonsNucleon-nucleonThresholdFísica-Modelos matemáticosFísica matemática