Three flavours of Hybrid or $\pi$ exhange: which is more attractive?

Abstract

This review summarises issues that have arisen since the appearance of "Rumsfeld Hadrons". We show that signals $\phi(2175)$; Y(4260) and $\Upsilon(10890)$ in the \ssbar, \cc and \bb share features that point to the possible role of $\pi$ exchange forces between flavoured mesons generating effects that can mimic hybrid mesons. The flavour dependence of these phenomena may help to resolve this question.