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 $\varphi (2175)$; Y(4260) and ${\rm Y}(10890)$ 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.

Plenary talk at XII Conference on Hadron Spectroscopy, Frascati 2007