Evidence that the a0(980) and f0(980) are not elementary particles

We study the interesting problem of whether it is possible to distinguish composite from elementary particles. In particular we generalize a model-independent approach of Weinberg to the case of unstable particles. This allows us to apply our formalism to the case of the a(0)(980) and f(0)(980) resonances and to address the question whether these particles are predominantly genuine, confined quark states (of (q) over barq or qq (q) over bar(q) over bar structure) or governed by mesonic components. (C) 2004 Elsevier B.V. All rights reserved.