The nature of σ, κ, a0(980) and f0(980)

Masses and widths of the four light scalar mesons σ, κ, a0(980) and f0(980) may be reproduced in a model where mesons scatter via a qq¯ loop. A transition potential is used to couple mesons to qq¯ at a radius of ∼0.57fm. Inside this radius, there is an infinite bare spectrum of confined qq¯ states, for which a harmonic oscillator is chosen here. The coupled-channel system approximately reproduces the features of both light and heavy meson spectroscopy. The generation of σ, κ, a0(980) and f0(980) is a balance between attraction due to the qq¯ loop and suppression of the amplitudes at the Adler zeros. Phase shifts increase more rapidly as the coupling constant to the mesons increases. This leads to resonant widths which decrease with increasing coupling constant-a characteristically non-perturbative effect.