Complex Meson Spectroscopy
  We do meson spectroscopy by studying the behavior of S-matrix poles in the complex-energy plane, as a function of the coupling strength for triplet-P-zero quark-pair creation. Thereto, a general formula for non-exotic hadron-hadron scattering involving arbitrary quark confinement is used, which can be applied to all flavors. We find two distinct types of poles, which we call "confinement" and "continuum" poles, respectively. Together, they suffice to understand the experimental meson spectrum. 
Eef van Beveren, Frieder Kleefeld, George Rupp