Evidence of $Q^2{\overline{Q}}^2$ Mesons in $\overline{p}n$ Annihilations and $\gamma \gamma$ Reactions

A new resonance at 1480 MeV with a width of 110 MeV is found in $\overline{p}n$ annihilations in the channel $\overline{p}n\to {\pi }^{-}{X}_0\mathrm{}\left(1480\right)\mathrm{}\to {\pi }^{-}{\rho }^0{\rho }^0$. Its mass, width, spin, and parity are shown to be consistent with the ${\rho }^0{\rho }^0$ enhancement observed in $\gamma \gamma$ reactions. Together with the suppression in the $\gamma \gamma \to {\rho }^{+}{\rho }^{-}$ data which requires the admixture of an isotensor structure, this ${\rho }^0{\rho }^0$ resonance in $\overline{p}n$ annihilation and $\gamma \gamma$ reactions and their small $\pi \pi$ branching ratios represent the best evidence yet for $Q^2{\overline{Q}}^2$ states. A ${\rho }^{-}{\rho }^{-}$ resonance in $\overline{p}n$ annihilations which would betray the exotic isotensor nature of the resonance is predicted.