The non-ordinary Regge behavior of the K_(0)^(*)(800) or κ-meson versus the ordinary K_(0)^(*) (1430)

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The Regge trajectory of an elastic resonance can be calculated from dispersion theory, instead of fitted phenomenologically, using only its pole parameters as input. This also provides a correct treatment of resonance widths in Regge trajectories, essential for very wide resonances. In this work we first calculate the K_(0)^(*)(1430) Regge trajectory, finding the ordinary almost real and linear behavior, typical of q (q) over bar resonances. In contrast, for the K_(0)^(*)(800) meson, the resulting Regge trajectory is non-linear and has a much smaller slope than ordinary resonances, being remarkably similar to that of the f_(0)(500) or σ meson. The slope of these unusual Regge trajectories seems to scale with themeson masses rather than with scales typical of quark degrees of freedom. We also calculate the range of the interaction responsible for the formation of these resonances. Our results strongly support a non- ordinary, predominantly meson-meson- like, interpretation for the lightest strange and non-strange resonances.
©Springer. Work supported by the Spanish Projects FPA2014-53375-C2-2, FPA2016-75654-C2-2-P and the group UPARCOS and the Spanish Excellence network HADRONet FIS2014-57026-REDT. A. Rodas would also like to acknowledge the financial support of the Universidad Complutense de Madrid through a predoctoral scholarship.
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