Evidence of the low-lying baryon Σ^*(1/2^-) in the process Λ_c^+→ηπ^+Λ

Motivated by the Belle measurements of the process Λ_c^+→ηπ^+Λ, we investigate this process by considering the contributions from the Λ(1670), a_0(980), and Σ(1385). In addition, we also consider the predicted low-lying baryon Σ^*(1/2^-). Our results involving the Σ^*(1/2^-) are favored by fitting to the Belle data of the ηΛ and π^+Λ invariant mass distributions. Furthermore, we predict the ηπ^+ invariant mass distribution and the angular distribution dΓ/d cosθ, which are significantly different depending on whether or not the contribution from the Σ^*(1/2^-) is considered. Finally, we show that, with the contribution from the Σ^*(1/2^-), the calculated Dalizt plot agrees with the Belle measurements. Future precise measurements of the process Λ_c^+→ηπ^+Λ could shed further light on the existence of the low-lying Σ^*(1/2^-).