Measurement of the $e^{+}{e}^{-}\to \ddot{I}{€}^{+}\ddot{I}{€}^{-}\ddot{I}{€}^0$ cross section in the energy region from 0.56 to 1.1 GeV with the SND detector

Abstract

The precise measurement of the $e^{+}{e}^{-}\to \ddot{I}{€}^{+}\ddot{I}{€}^{-}\ddot{I}{€}^0$ cross section is performed in the center-of-mass energy range $E=560$--1100 MeV using a data sample of 66 pb${}^{-1}$ collected in the experiment with the SND detector at the VEPP-2000 $e^{+}{e}^{-}$ collider. The systematic uncertainty of the cross section measurement is 0.9\% at the maximum of the $\ddot{I}‰$ resonance and 1.2\% at the maximum of the $\ddot{I}•$ resonance. The leading-order hadronic contribution to the muon magnetic anomaly calculated using the $e^{+}{e}^{-}\to \ddot{I}{€}^{+}\ddot{I}{€}^{-}\ddot{I}{€}^0$ cross section measured by SND from 0.62 to 1.975 GeV is $(45.95\pm 0.06\pm 0.46)\times 10^{-10}$. From the fit to the cross section data with the vector meson dominance model, the parameters of the $\ddot{I}‰$, $\ddot{I}$, and $\ddot{I}•$ resonances are obtained. The obtained values of $\mathcal{B}(\ddot{I}‰\to e^{+}{e}^{-})\mathcal{B}(\ddot{I}‰\to 3\ddot{I}€)$, mass and width of the $\ddot{I}‰$ meson, and $\mathcal{B}(\ddot{I}\to 3\ddot{I}€)$ have accuracy better than the current world average values.

39 pages, 18 figures