Researchers have studied the decay of the J/ψ meson into ΛπΣ̄ to identify excited states of the Sigma (Σ) baryon. This analysis focused on the invariant mass distribution of the πΛ system at low energies. In addition to a clear signal of the well-established Σ(1385) (J^P = 3/2^+) state, a smaller peak corresponding to the Σ(1430) (J^P = 1/2^-) was detected, whose existence had been previously confirmed by the Belle Collaboration.

The initial study, which only considered the πΛ interaction, suggested that the low-energy part of the spectrum is better reproduced by including contributions from both the Σ(1430) and a theoretically predicted Σ(1380) (J^P = 1/2^-) state, whose existence had been previously claimed from analyses of different experiments. However, when the πΣ̄ interaction was incorporated into the model, the need to include the Σ(1380) disappeared, indicating that the interpretation of these resonances can significantly depend on the interactions considered in the analysis.

The identification and characterization of these excited baryonic states are crucial for understanding the internal structure of hadrons and strong interactions. Sigma baryons are particles composed of three quarks (uds or uus), and their excited states provide valuable information about quark models and quantum chromodynamics at low energies. This type of experiment contributes to refining our knowledge of the hadronic mass spectrum and testing the predictions of the theory of strong interactions.