Study of e plus e--> sigma 0 sigma over bar 0 and sigma plus sigma over bar - by initial state radiation method at Belle

The processes e+e-→ς0ς¯0 and e+e-→ς+ς¯- are studied using initial-state-radiation events in a sample of 980 fb-1 collected with the Belle detector at the KEKB asymmetric-energy e+e- collider. The cross sections from the mass threshold to 3 GeV/c2 and the effective form factors of ς0 and ς+ are measured. In the charmonium region, we observe the decays J/ψ→ς0ς¯0 and J/ψ→ς+ς¯- and determine the respective branching fractions.