δ(980)as a four-quark state and the radiative decays of vector and scalar mesons

Abstract

A large phenomenological value for the decay rate $\ensuremath{\Gamma}(\ensuremath{\delta}\ensuremath{\rightarrow}\ensuremath{\gamma}\ensuremath{\gamma})$ contradicts the very small values obtained in a model assuming the $\ensuremath{\delta}(980)$ is a two-quark state, implying that the $\ensuremath{\delta}$ should be treated as a four-quark state. The Okuba-Zweig-Iizuka rule then gives a large ratio of the $\ensuremath{\delta}\ensuremath{-}\ensuremath{\rho}\ensuremath{-}\ensuremath{\varphi}$ to $\ensuremath{\delta}\ensuremath{-}\ensuremath{\rho}\ensuremath{-}\ensuremath{\omega}$ couplings which is opposite to previous estimates based on vector dominance. Previous calculations of $\ensuremath{\delta}$ radiative decays and three-body radiative decays of vector mesons are modified and new decay rates are obtained.