Study of the decay $J/\ddot{I}ˆ\to \ddot{I}•\ddot{I}{€}^0\hat{I}\cdot$

Abstract

Based on $(10.09\pm 0.04)\times 10^9$ $J/\ddot{I}ˆ$ events collected with the BESIII detector operating at the BEPCII collider, a partial wave analysis of the decay $J/\ddot{I}ˆ\to \ddot{I}•\ddot{I}{€}^0\hat{I}\cdot$ is performed. We observe for the first time two new structures on the $\ddot{I}•\hat{I}\cdot$ invariant mass distribution, with statistical significances of $24.0\ddot{I}ƒ$ and $16.9\ddot{I}ƒ$; the first with $J^{\mathrm{PC}}$ = $1^{+-}$, mass M = (1911 $\pm$ 6 (stat.) $\pm$ 14 (sys.))~MeV/$c^2$, and width $\hat{I}“=$ (149 $\pm$ 12 (stat.) $\pm$ 23 (sys.))~MeV, the second with $J^{\mathrm{PC}}$ = $1^{--}$, mass M = (1996 $\pm$ 11 (stat.) $\pm$ 30 (sys.))~MeV/$c^2$, and width $\hat{I}“$ = (148 $\pm$ 16 (stat.) $\pm$ 66 (sys.))~MeV. These measurements provide important input for the strangeonium spectrum. In addition, the $f_0(980)-a_0(980{)}^0$ mixing signal in $J/\ddot{I}ˆ\to \ddot{I}•f_0(980)\to \ddot{I}•a_0(980{)}^0$ and the corresponding electromagnetic decay $J/\ddot{I}ˆ\to \ddot{I}•a_0(980{)}^0$ are measured with improved precision, providing crucial information to understand the nature of $a_0(980{)}^0$ and $f_0(980)$.