Double triangle cusps relevant to Pc(4312)+ , Pc(4380)+, and Pc(4457)+

A novel scenario is proposed for hidden charm pentaquark (Pc)-like structures in Λ 0 b → J/ψpK−. The scenario is based on kinematical singularities arising from double triangle mechanisms. Anomalous threshold cusps due to the singularities are, compared with ordinary P(∗) c D¯(∗) one-loop thresh-old cusp, significantly more singular. It is demonstrated that an interference among the double triangle mechanisms and other common mechanisms generates peaks very similar to the Pc(4312)+, Pc(4380)+, and Pc(4457)+ peak structures. While hadron molecules and compact pentaquarks have been common models to explain the Pc states, the present model is a completely different one. The present model includes only one pentaquark state Pc(4440)+. However, we find that the Pc(4440)+ width and strength are significantly smaller than those from the LHCb analysis. The P + c signals are searched for in J/ψ photoproduction but not found. A search was also made in Λ 0 b → J/ψpπ− data, finding only a possible P c(4440)+-like signal. The present model is consistent with the experimental situation