Identifying $Σ(1380)$ and $Σ(1430)$ in the $J/ψ\to Λπ\barΣ$ reaction

We study the $J/\psi \to \Lambda \pi \bar{\Sigma}$ reaction by looking at the $\pi^+ \Lambda$ mass distribution at low energies, in search of signals for the low lying $\Sigma^+$ states. Apart from a clear signal of the $\Sigma(1385) (3/2^+)$ state, we find a smaller peak for the predicted $\Sigma(1430) (1/2^-)$, which has already been confirmed by the Belle Collaboration. A first analysis, considering only the $\pi\Lambda$ interaction, shows that the low energy part of the spectrum is better reproduced including contributions from the $\Sigma(1430)$ and the predicted $\Sigma(1380)(1/2^-)$ state that has been claimed before from analyses of different experiments. However, when we consider the $\pi\bar{\Sigma}$ interaction the need for the $\Sigma(1380)$ disappears.