Abstract :
We show that the κ, a0(980), σ and the f0(980) resonances constitute the lightest scalar nonet in three different and complementary ways. First, by establishing the continuous movement of the poles from the physical to a generic SU(3) limit. Second, by performing an analysis of the couplings of the scalar mesons to pairs of pseudoscalars and third, by analysing the couplings of the scalars with meson–meson SU(3) scattering eigenstates. Both of the last two methods agree that the mixing angle between the singlet and the octet I=0 states is θ=19°±5 degrees, so that the σ is mainly the singlet and the f0(980) the isosinglet octet state.
