Remarks on the Pc structures and triangle singularities

Abstract

It was proposed that the narrow Pc(4450) structure observed by the LHCb Collaboration in the reaction Λb→ J/ ψpK might be due to a triangle singularity around the χc1-proton threshold at 4.45 GeV. We discuss the occurrence of a similar triangle singularity in the J/ ψp invariant mass distribution for the decay Λb→ J/ ψpπ, which could explain the bump around 4.45 GeV in the data. More precise measurements of this process would provide valuable information towards an understanding of the Pc structures.