Study of light scalar mesons through $D_s^{+}\to \ddot{I}{€}^0\ddot{I}{€}^0{e}^{+}\hat{I}{½}_e$ and $K_S^0{K}_S^0{e}^{+}\hat{I}{½}_e$ decays

Abstract

Using 6.32~fb${}^{-1}$ of $e^{+}{e}^{-}$ collision data recorded by the BESIII detector at center-of-mass energies between $4.178$ to $4.226$ GeV, we present the first measurement of the decay $D_s^{+}\to f_0(980)e^{+}\hat{I}{½}_e,f_0(980)\to \ddot{I}{€}^0\ddot{I}{€}^0$. The product branching fraction of $D_s^{+}\to f_0(980)e^{+}\hat{I}{½}_e,f_0(980)\to \ddot{I}{€}^0\ddot{I}{€}^0$ is measured to be $(7.9\pm 1.4_{\mathrm{stat}}\pm 0.3_{\mathrm{syst}})\times 10^{-4}$, with a statistical significance of $7.8\ddot{I}ƒ$. Furthermore, the upper limits on the product branching fractions of $D_s^{+}\to f_0(500)e^{+}\hat{I}{½}_e$ with $f_0(500)\to \ddot{I}{€}^0\ddot{I}{€}^0$ and the branching fraction of $D_s^{+}\to K_S^0{K}_S^0{e}^{+}\hat{I}{½}_e$ are set to be $7.3\times 10^{-4}$ and $3.8\times 10^{-4}$ at 90\% confidence level, respectively. Our results provide valuable inputs to the understanding of the structures of light scalar mesons.