Evidence for a new $\Sigma^{*}$ resonance with $J^P=1/2^-$ in the old data of $K^-p\to\Lambda\pi^+\pi^-$ reaction

TL;DR

Reanalysis of old $K^-p o \Lambda\pi^+\pi^-$ data suggests evidence for a new $\Sigma^* ext{ }(1/2^-)$ resonance near 1385 MeV, differing from the well-known $\Sigma^*(1385)$ with $3/2^+$.

Contribution

This study provides evidence for a previously unconfirmed $\Sigma^* ext{ }(1/2^-)$ resonance, challenging existing quark model predictions and highlighting the need for higher-statistics data.

Findings

Evidence for a new $\Sigma^*$ resonance with $J^P=1/2^-$.

The new resonance is around 1385 MeV, similar to the $\Sigma^*(1385)$ mass.

Indications of a broader decay width for the new state.

Abstract

Distinctive patterns are predicted by quenched quark models and unquenched quark models for the lowest SU(3) baryon nonet with spin parity $J^P=1/2^-$. While the quenched quark models predict the lowest $1/2^-$ $\Sigma^*$ resonance to be above 1600 MeV, the unquenched quark models predict it to be around $\Sigma^*(1385)$ energy. Here we re-examine some old data of the $\kp \to \la$ reaction and find that besides the well established $\Sigma^{*}(1385)$ with $J^P=3/2^+$, there is indeed some evidence for the possible existence of a new $\Sigma^{*}$ resonance with $J^P=1/2^-$ around the same mass but with broader decay width. Higher statistic data on relevant reactions are needed to clarify the situation.