# The non-ordinary Regge behavior of the K*0(800) or Kappa-meson versus the ordinary K*0(1430)

## TL;DR

This paper calculates the Regge trajectories of the K*0(1430) and K*0(800) mesons, revealing ordinary quark-antiquark behavior for the former and non-ordinary, meson-meson-like behavior for the latter, challenging traditional resonance models.

## Contribution

It introduces a dispersion theory-based method to compute Regge trajectories directly from pole parameters, highlighting non-ordinary behavior of the K*0(800) meson.

## Key findings

- K*0(1430) has an almost real, linear Regge trajectory typical of quark-antiquark states.
- K*0(800) exhibits a non-linear, small-slope trajectory similar to the sigma meson.
- The Regge slope correlates with meson mass rather than quark degrees of freedom.

## Abstract

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 quark-antiquark 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 f0(500) or sigma meson. The slope of these unusual Regge trajectories seems to scale with the meson 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.