Study of the decay ${D}_{s}^{+}\to {K}_{S}^{0}{K}_{S}^{0}{\pi }^{+}$ and observation of an isovector partner to ${f}_{0}\left(1710\right)$

Using ${e}^{+}{e}^{-}$ annihilation data corresponding to a total integrated luminosity of $6.32\text{}\text{}f{b}^{-1}$ collected at center-of-mass energies between 4.178 and 4.226 GeV with the BESIII detector, we perform an amplitude analysis of the decay ${D}_{s}^{+}\to {K}_{S}^{0}{K}_{S}^{0}{\pi }^{+}$ for the first time. An enhancement is observed in the ${K}_{S}^{0}{K}_{S}^{0}$ mass spectrum near $1.7\text{}\text{}\mathrm{GeV}/{c}^{2}$, which was not seen in ${D}_{s}^{+}\to {K}^{+}{K}^{-}{\pi }^{+}$ in an earlier work, implying the existence of an isospin one partner of the ${f}_{0}\left(1710\right)$. The branching fraction of the decay ${D}_{s}^{+}\to {K}_{S}^{0}{K}_{S}^{0}{\pi }^{+}$ is determined to be $B\left({D}_{s}^{+}\to {K}_{S}^{0}{K}_{S}^{0}{\pi }^{+}\right)=\left(0.68±0.0{4}_{\mathrm{stat}}±0.0{1}_{\mathrm{syst}}\right)%$.