Study of dynamics of the process $e^{+}{e}^{-}\to \ddot{I}{€}^{+}\ddot{I}{€}^{-}\ddot{I}{€}^0$ in the energy range 1.15--2.00 GeV

Abstract

The dynamics of the process $e^{+}{e}^{-}\to \ddot{I}{€}^{+}\ddot{I}{€}^{-}\ddot{I}{€}^0$ is studied in the energy region from 1.15 to 2.00 GeV using data accumulated with the SND detector at the VEPP-2000 $e^{+}{e}^{-}$ collider. The Dalitz plot distribution and $\ddot{I}{€}^{+}\ddot{I}{€}^{-}$ mass spectrum are analyzed in a model including the intermediate states $\ddot{I}(770)\ddot{I}€$, $\ddot{I}(1450)\ddot{I}€$, and $\ddot{I}‰\ddot{I}{€}^0$. As a result, the energy dependences of the $\ddot{I}(770)\ddot{I}€$ and $\ddot{I}(1450)\ddot{I}€$ cross sections and the relative phases between the $\ddot{I}(770)\ddot{I}€$ amplitude and the $\ddot{I}(1450)\ddot{I}€$ and $\ddot{I}‰\ddot{I}{€}^0$ amplitudes are obtained. The $\ddot{I}(1450)\ddot{I}€$ cross section has a peak in the energy region of the $\ddot{I}‰(1650)$ resonance (1.55-1.75 GeV). In this energy range the contributions of the $\ddot{I}(770)\ddot{I}€$ and $\ddot{I}(1450)\ddot{I}€$ states are of the same order of magnitude. No resonance structure near 1.65 GeV is observed in the $\ddot{I}(770)\ddot{I}€$ cross section. We conclude that the intermediate state $\ddot{I}(1450)\ddot{I}€$ gives a significant contribution to the decay of $\ddot{I}‰(1650)\to \ddot{I}{€}^{+}\ddot{I}{€}^{-}\ddot{I}{€}^0$, whereas the $\ddot{I}(770)\ddot{I}€$ mechanism dominates in the decay $\ddot{I}‰(1420)\to \ddot{I}{€}^{+}\ddot{I}{€}^{-}\ddot{I}{€}^0$.

9 pages, 7 figures, 3 tables