Evidence of the low-lying baryon $\Sigma^*(1/2^-)$ in the process $\Lambda_c^+\to \eta\pi^+\Lambda$

TL;DR

This paper investigates the process $\Lambda_c^+ o \eta\pi^+\Lambda$ and provides evidence supporting the existence of the low-lying baryon $\Sigma^*(1/2^-)$, using Belle experimental data and theoretical modeling.

Contribution

It introduces the consideration of the predicted $\Sigma^*(1/2^-)$ baryon in analyzing the decay process, improving the fit to experimental data and making new predictions.

Findings

The $\Sigma^*(1/2^-)$$ contribution improves data fit.

Predicted invariant mass and angular distributions differ with/without $\Sigma^*(1/2^-)$.

Dalitz plot analysis supports the existence of $\Sigma^*(1/2^-)$.

Abstract

Motivated by the Belle measurements of the process $\Lambda_c^+\to \eta\pi^+\Lambda$, we investigate this process by considering the contributions from the $\Lambda(1670)$, $a_0(980)$, and $\Sigma(1385)$. In addition, we also consider the predicted low-lying baryon $\Sigma^*(1/2^-)$. Our results involving the $\Sigma^*(1/2^-)$ are favored by fitting to the Belle data of the $\eta\Lambda$ and $\pi^+\Lambda$ invariant mass distributions. Furthermore, we predict the $\eta\pi^+$ invariant mass distribution and the angular distribution $d\Gamma/d{\rm cos}\theta$, which are significantly different depending on whether or not the contribution from the $\Sigma^*(1/2^-)$ is considered. Finally, we show that, with the contribution from the $\Sigma^*(1/2^-)$, the calculated Dalizt plot agrees with the Belle measurements. Future precise measurements of the process $\Lambda_c^+\to \eta\pi^+\Lambda$ could shed further light on the existence of the low-lying $\Sigma^*(1/2^-)$.