Evidence of the low-lying baryon ${\Sigma }^{\ast }(1/2^{-})$ in the process ${\Lambda }_c^{+}\to \eta {\pi }^{+}\Lambda$

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 ${\Sigma }^{\ast }(1/2^{-})$. Our results involving the ${\Sigma }^{\ast }(1/2^{-})$ 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 $d\Gamma /d\cos \theta$, which are significantly different depending on whether or not the contribution from the ${\Sigma }^{\ast }(1/2^{-})$ is considered. Finally, we show that, with the contribution from the ${\Sigma }^{\ast }(1/2^{-})$, 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 ${\Sigma }^{\ast }(1/2^{-})$.

Comments: 11 pages, 14 figures, comments are welcome