Production of σ in ψ(2S)→π+π−J/ψ

Using 14M ψ(2S) events accumulated by BESII at the BEPC, a covariant helicity amplitude analysis is performed for ψ(2S)→π+π−J/ψ, J/ψ→μ+μ−. The π+π− mass spectrum, distinctly different from phase space, suggests σ production in this process. Two different theoretical schemes are used in the global fit to the data. The results are consistent with the existence of the σ. The σ pole position is determined to be (552−106+84)−i(232−72+81) MeV/c2.