Analysis of $Σ^*$ via isospin selective reaction $K_Lp \to π^+Σ^0$

Abstract

The isospin-selective reaction $K_Lp \to π^+Σ^0$ provides a clean probe for investigating $I=1$ $Σ^*$ resonances. In this work, we perform an analysis of this reaction using an effective Lagrangian approach for the first time, incorporating the well-established $Σ(1189) 1/2^+$, $Σ(1385) 3/2^+$, $Σ(1670) 3/2^-$, $Σ(1775) 5/2^-$ states, while also exploring contributions from other unestablished states. By fitting the available differential cross section and recoil polarization data, adhering to partial-wave phase conventions same as PDG, we find that besides the established resonances, contributions from $Σ(1660) 1/2^+$, $Σ(1580) 3/2^-$ and a $Σ^*(1/2^-)$ improve the description. Notably, a $Σ^*(1/2^-)$ resonance with mass around 1.54 GeV, consistent with $Σ(1620)1/2^-$, is found to be essential for describing the data in this channel, a stronger indication than found in previous analyses focusing on $πΛ$ final states. While providing complementary support for $Σ(1660) 1/2^+$ and $Σ(1580) 3/2^-$, our results highlight the importance of the $Σ(1620) 1/2^-$ region in $K_Lp \to π^+Σ^0$. Future high-precision measurements are needed to solidify these findings and further constrain the $Σ^*$ spectrum.