First observation of the $\ddot{I}•\to \ddot{I}{€}^{+}\ddot{I}{€}^{-}{\hat{I}}^3$ decay

Abstract

Radiative decays of the $\ddot{I}•$ meson have been studied using a data sample of about 20 million $\ddot{I}•$ decays collected by the CMD-2 detector at VEPP-2M collider in Novosibirsk. From selected $e^{+}{e}^{-}\to \ddot{I}{€}^{+}\ddot{I}{€}^{-}{\hat{I}}^3$ events the $\ddot{I}•\to \ddot{I}{€}^{+}\ddot{I}{€}^{-}{\hat{I}}^3$ decay has been observed for the first time. \par Under the assumption that the intermediate $f_0(980){\hat{I}}^3$ state dominates in the $\ddot{I}•\to \ddot{I}{€}^{+}\ddot{I}{€}^{-}{\hat{I}}^3$ decay, the corresponding branching ratio is $Br(\ddot{I}•\to f_0(980){\hat{I}}^3)=(1.93\pm 0.46\pm 0.50)\times 10^{-4}$. \par Selected $e^{+}{e}^{-}\to \hat{I}{¼}^{+}\hat{I}{¼}^{-}{\hat{I}}^3$ events were used to obtain $Br(\ddot{I}•\to \hat{I}{¼}^{+}\hat{I}{¼}^{-}{\hat{I}}^3)=(1.43\pm 0.45\pm 0.14)\times 10^{-5}$ for $E_{\hat{I}}^3>20$ MeV. \par Using the same data sample, upper limits at 90% CL have been obtained for the C-violating decay of the $\ddot{I}•$: $Br(\ddot{I}•\to \ddot{I}{\hat{I}}^3)<1.2\times 10^{-5}$; and for the P- and CP-violating decay of the $\hat{I}\cdot$: \par $Br(\hat{I}\cdot \to \ddot{I}{€}^{+}\ddot{I}{€}^{-})<3.3\times 10^{-4}$.

16 pages, 10 figures, Submitted to Phys. Lett. B