Understanding the newly observed heavy pentaquark candidates

We find that several thresholds can contribute to the enhancements of the newly observed heavy pentaquark candidates P-c(+)(4380) and P-c(+)(4450) via the anomalous triangle singularity (ATS) transitions in the specific kinematics of Lambda(b) -> J/psi K(-)p. Apart from the observed two peaks we find that another peaks around 4.5 GeV can also be produced by the ATS. We also show that the Sigma(()(c)*()) can be produced at leading order in Lambda(b) decay. This process is different from the triangle diagram and its threshold enhancement only appears as CUSP effects if there is no pole structure or the ATS involved. The threshold interaction associated with the presence of the ATS turns out to be a general phenomenon and plays a crucial role in the understanding of candidates for exotic states. (C) 2016 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/). Funded by SCOAP(3).