Okubo-Zweig-Iizuka rule and lack of evidence for glueballs inπ−p→φφn

The Okubo-Zweig-Iizuka rule is a consequence of QCD. It is shown that in general disconnected diagrams are suppressed only if the gluons couple to the quark-antiquark pair of a single vector or tensor meson. Other disconnected diagrams are not strongly suppressed. It is shown that the threshold enhancement observed in ${\pi }^{-}p\to \phi \phi n$ is consistent with phenomenological expectations in the absence of resonances and thus does not contain any evidence for glueballs.