Search for the Σ⁎ state in Λc+→π+π0π−Σ+ decay by triangle singularity

Abstract

A Σ⁎ resonance with spin-parity JP=1/2− and mass in the vicinity of the K¯N threshold has been predicted in the unitary chiral approach and inferred from the analysis of CLAS data on the γp→K+π0Σ0 reaction. In this work, based on the dominant Cabibbo favored weak decay mechanism, we perform a study of Λc+→π+π0Σ⁎ with the possible Σ⁎ state decaying into π−Σ+ through a triangle diagram. This process is initiated by Λc+→π+K¯⁎N, then the K¯⁎ decays into K¯π and K¯N produce the Σ⁎ through a triangle loop containing K¯⁎NK¯ which develops a triangle singularity. We show that the π−Σ+ state is generated from final state interaction of K¯N in S-wave and isospin I=1, and the Λc+→π+π0π−Σ+ decay can be used to study the possible Σ⁎ state around the K¯N threshold. The proposed decay mechanism can provide valuable information on the nature of the Σ⁎ resonance and can in principle be tested by facilities such as LHCb, BelleII and BESIII.