Observation of $a^{0}_{0}(980)$-$f_{0}(980)$ Mixing
We report the first observation of $a^{0}_{0}(980)$-$f_{0}(980)$ mixing in the decays of $J/ψ\toϕf_{0}(980)\toϕa^{0}_{0}(980)\toϕηπ^{0}$ and $χ_{c1}\to a^{0}_{0}(980)π^{0}\to f_{0}(980)π^{0}\toπ^{+}π^{-}π^{0}$, using data samples of $1.31\times10^{9}$ $J/ψ$ events and $4.48\times10^{8}$ $ψ(3686)$ events accumulated with the BESIII detector. The signals of $f_{0}(980)\to a^{0}_{0}(980)$ and $a^{0}_{0}(980)\to f_{0}(980)$ mixing are observed at levels of statistical significance of $7.4σ$ and $5.5σ$, respectively. The corresponding branching fractions and mixing intensities are measured and the constraint regions on the coupling constants, $g_{a_{0}K^{+}K^{-}}$ and $g_{f_{0}K^{+}K^{-}}$, are estimated. The results improve the understanding of the nature of $a^{0}_{0}(980)$ and $f_{0}(980)$.