Evidence on $qq\bar{q}\bar{q}$ Hadron Spectrum from $\gamma \gamma \to vectormesonvectormeson$ Reactions?

Abstract

The $\gamma \gamma \to {\rho }^0{\rho }^0\to 4\pi$ reaction shows a broad "resonance"at 1.5 GeV with no counterpart in the ${\rho }^{+}{\rho }^{-}$ channel. This $(J^P,J_z)=(2^{+},2)$, $I=0$, and $2$ resonance is considered as a candidate for a $qq\bar{q}\bar{q}$ state. We show, however, that it can also be explained by potential scattering of ${\rho }^0{\rho }^0$ via the $\sigma -$ exchange.

Comments: talk presented at the Int. Conf. on Quark Confinement and Hadron Spectrum, Como, 20.-24.6.1994, to be published in the Proceedings, 3 pages, 1 figure (available from the authors upon request)