Measurement of Σ

Using collision data collected with the BESIII detector at seven energy points ranging from 3.68 to 3.71 GeV and corresponding to an integrated luminosity of 652 1 pb 1 , we present an energy-dependent measurement of the transverse polarization, relative phase and modulus ratio of the electromagnetic form factors of the Σ hyperon in the → reaction. At each energy point, no evident polarization is observed. These results are helpful to understand the production mechanism of the Σ - pairs.