Measurements of $\Sigma $ electromagnetic form factors in the timelike region using the untagged initial-state radiation technique

The process ${e}^{+}{e}^{-}\to {\Sigma }^{+}{\overline{\Sigma }}^{-}$ is studied from threshold up to $3.04\text{}\text{}\mathrm{GeV}/{c}^{2}$ via the initial-state radiation technique using data with an integrated luminosity of $12.0\text{}\text{}{\mathrm{fb}}^{-1}$, collected at center-of-mass energies between 3.773 and 4.258 GeV with the BESIII detector at the BEPCII collider. The pair production cross sections and the effective form factors of $\Sigma $ are measured in eleven ${\Sigma }^{+}$${\overline{\Sigma }}^{-}$ invariant mass intervals from threshold to $3.04\text{}\text{}\mathrm{GeV}/{c}^{2}$. The results are consistent with the previous results from Belle and BESIII. Furthermore, the branching fractions of the decays $J/\psi \to {\Sigma }^{+}{\overline{\Sigma }}^{-}$ and $\psi \left(3686\right)\to {\Sigma }^{+}{\overline{\Sigma }}^{-}$ are determined and the obtained results are consistent with the previous results of BESIII.