Study of the $\ddot{I}€\ddot{I}€$ mass spectra in the process $e^{+}{e}^{-}\to \ddot{I}{€}^{+}\ddot{I}{€}^{-}\ddot{I}{€}^0$ at $\sqrt[]{s}\simeq 1020$ MeV

Abstract

The invariant mass spectra of the $\ddot{I}{€}^{+}\ddot{I}{€}^{-}$ and $\ddot{I}{€}^{\pm }\ddot{I}{€}^0$ pairs in the process $e^{+}{e}^{-}\to \ddot{I}{€}^{+}\ddot{I}{€}^{-}\ddot{I}{€}^0$ were studied in the SND experiment at the VEPP-2M collider in the energy region $\sqrt[]{s}\simeq 1020$ MeV. These studies were based on about $0.5\times 10^6$ experimental events. The spectra were analyzed in the framework of the vector meson dominance model. It was found that the experimental data can be described with $e^{+}{e}^{-}\to \ddot{I}\ddot{I}€\to \ddot{I}{€}^{+}\ddot{I}{€}^{-}\ddot{I}{€}^0$ transition only. Upper limit on the branching ratio of the $\ddot{I}•(1020)\to \ddot{I}{€}^{+}\ddot{I}{€}^{-}\ddot{I}{€}^0$ decay through intermediate states different from $\ddot{I}\ddot{I}€$ was obtained at the 90 % confidence level: $B(\ddot{I}•\to \ddot{I}{€}^{+}\ddot{I}{€}^{-}\ddot{I}{€}^0)<6\cdot 10^{-4}$. The $\ddot{I}$-meson mass and width which follow from the spectra analysis are $m_{\ddot{I}}=775.0\pm 1.3$ MeV, $\hat{I}{“}_{\ddot{I}}=150.4\pm 3.0$ MeV. Neutral and charged $\ddot{I}$-mesons mass difference was found to equal $m_{\ddot{I}{}^{\pm }}-m_{\ddot{I}{}^0}=-1.3\pm 2.3$ MeV. In the $\ddot{I}{€}^{+}\ddot{I}{€}^{-}$ mass spectrum the $\ddot{I}-\ddot{I}‰$ interference was seen at two standard deviations level.

22 pages REVTEX and 19 figures