Even though the Standard Model has achieved great success, its application to the field of low energy still lacks solid foundation due to our limited knowledge on nonperturbative QCD. Practically, all theoretical calculations of the hadronic transition matrix elements are based on various phenomenological models. There indeed exist some anomalies in the field that are waiting for interpretations. The goal of this work is trying to solve one of the anomalies: the discrepancy between the theoretical prediction on the sign of the up-down asymmetry parameter of Λ c → Σ π and the experimental measurement. In the literatures several authors calculated the rate and determined the asymmetry parameter within various schemes, but there exist obvious loopholes in those adopted scenarios. To solve the discrepancy between theory and data, we suggest that not only the direct transition process contributes to the observed Λ c → Σ π , but also other portals such as Λ c → Λ ρ play a substantial role via an isospin-conserving rescattering Λ ρ → Σ π . Taking into account the effects induced by the final state interaction, we reevaluate the relevant quantities. Our theoretical prediction based on this scenario involving an interference between the direct transition of Λ c → Σ π and the portal Λ c → Λ ρ → Σ π can make both the decay rate and sign of the asymmetry parameter to be consistent with data.
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