Study of the process $e^{+}{e}^{-}\to \ddot{I}{€}^{+}\ddot{I}{€}^{-}\ddot{I}{€}^0$ in the energy region $\sqrt[]{s}$ below 0.98 GeV

Abstract

The cross section of the process $e^{+}{e}^{-}\to \ddot{I}{€}^{+}\ddot{I}{€}^{-}\ddot{I}{€}^0$ was measured in the Spherical Neutral Detector (SND) experiment at the VEPP-2M collider in the energy region $\sqrt[]{s}$ below 980 MeV. This measurement was based on about $1.2\times 10^6$ selected events. The obtained cross section was analyzed together with the SND and DM2 data in the energy region $\sqrt[]{s}$ up to 2 GeV. The $\ddot{I}‰$-meson parameters: $m_{\ddot{I}}‰=782.79\pm 0.08\pm 0.09$ MeV, $\hat{I}{“}_{\ddot{I}}‰=8.68\pm 0.04\pm 0.15$ MeV and $\ddot{I}ƒ(\ddot{I}‰\to 3\ddot{I}€)=1615\pm 9\pm 57$ nb were obtained. It was found that the experimental data cannot be described by a sum of only $\ddot{I}‰$, $\ddot{I}•$, $\ddot{I}{‰}^{\prime }$ and $\ddot{I}{‰}^{\prime \prime }$ resonances contributions. This can be interpreted as a manifestation of $\ddot{I}\to 3\ddot{I}€$ decay, suppressed by $G$-parity, with relative probability $B(\ddot{I}\to 3\ddot{I}€)=(1.01{\pm }_{0.36}^{0.54}\pm 0.034)\times 10^{-4}$.

41 pages REVTEX and 34 figures