Consequences of quark-line (Okubo-Zweig-Iizuka) rule

Consequences of the validity of the quark-line (Okubo-Zweig-Iizuka) rule have been studied both theoretically and experimentally. The present experimental data are consistent with the validity of the rule for 1^- and possibly 2⁺ nonets. With respect to the 0^- nonet, the rule is in reasonable agreement, if we consider a suitable mixing scheme for the η-η^' complex. Theoretical implications of these facts are also discussed. The possible violation of the rule has been estimated to be 6% for the 1^- nonet and 15% for the 0^- nonet.