Pole Analysis on Unitarized SU(3) × SU(3) One Loop χPT Amplitudes

We analyze ππ-KK-bar and πη-KK-bar couple channel [1,1] matrix Padé amplitudes of SU(3) × SU(3) chiral perturbation theory. By fitting phase shift and inelasticity data, we determine pole positions in different channels (f0(980), a0(980), f0(600), K*0(800), K*(892), ρ(770)) and trace their Nc trajectories. We stress that a couple channel Breit-Wigner resonance should exhibit two poles on different Riemann sheets and meet each other on the real axis when Nc = ∞. Poles are hence classified using this criteria and we conclude that K* (892) and ρ(770) are unambiguous Breit-Wigner resonances. For scalars the situation is much less clear. We find that f0(980) is a molecular state rather than a Breit-Wigner resonance, while a0(980), though behave oddly when varying Nc, do maintain a twin pole structure. (physics of elementary particles and fields)