Study of the spectrum of the Σ(1193) excited states, Σ^*, with isospin I = 1 and strangeness S = −1 is one of the most important issues in hadronic physics. The Λp->ΛpΠ⁰reaction is a very good isospin 1 filter for studying Σ^*resonances decaying to ΛΠ, and provides a useful tool for testing Σ^*baryon models.

Researchers at the Institute of Modern Physics, Chinese Academy of Sciences (IMP) study the Λp->ΛpΠ⁰reaction near threshold within an effective Lagrangian method and the isobar model. The production process is described by single-pion and single-kaon exchange. In addition to the role played by the Σ^*(1385) resonance of spin-parity J^P= 3/2⁺, the effects of a newly proposed Σ^*(J^P= 1/2⁻) state with mass and width around 1380 MeV and 120 MeV are investigated. It is found that the model leads to a good description of the experimental data on the total cross section (see Fig. 1) of the Λp->ΛpΠ⁰reaction by including the contributions from the possible Σ^*(1/2⁻) state. However, the theoretical calculations by considering only theΣ^*(1385) resonance fail to reproduce the experimental data, especially for the enhancement close to the reaction threshold, which indicates that the Λp->ΛpΠ⁰data support the existence of this Σ^*(1380) state, and more accurate data for this reaction can be used to improve our knowledge of the Σ^*(1380) properties. The present calculation offers some important clues for the mechanisms of the Λp->ΛpΠ⁰reaction and is the first effort at studying the role of the Σ^*(1380) state in a relevant reaction.

The related results have been published inPhys. Rev. C 90, 055204 (2014).

DOI：http://journals.aps.org/prc/abstract/10.1103/PhysRevC.90.055204