Symmetrization selection rules for the decay of four-quark states to two J=0 mesons are analysed in a non - field theoretic context with isospin symmetry. The OZI allowed decay of an isoscalar J^PC = (1,3,...)^{-+} exotic state to eta' eta or f_0' f_0 is only allowed for four-quark components of the state containing one s sbar pair, providing a filter for strangeness content in these states. Decays of four-quark a_0 states are narrower than otherwise expected. If the experimentally observed 1^{-+} enhancement in eta pi is resonant, it is qualitatively in agreement with being a four-quark state.
@article{arxiv.hep-ph/0007216,
title = {Filter for strangeness in J^{PC} exotic four-quark states},
author = {Philip R. Page},
journal= {arXiv preprint arXiv:hep-ph/0007216},
year = {2009}
}