Hidden charm pentaquark and Λ(1405) in the Λb0→ηcK−p(πΣ) reaction

We have performed a study of the Λb0→ηcK−p and Λb0→ηcπΣ reactions based on the dominant Cabibbo favored weak decay mechanism. We show that the K−p produced only couples to Λ⁎ states, not Σ⁎ and that the πΣ state is only generated from final state interaction of K¯N and ηΛ channels which are produced in a primary stage. This guarantees that the πΣ state is generated in isospin I=0 and we see that the invariant mass produces a clean signal for the Λ(1405) of higher mass at 1420 MeV. We also study the ηcp final state interaction, which is driven by the excitation of a hidden charm resonance predicted before. We relate the strength of the different invariant mass distributions and find similar strengths that should be clearly visible in an ongoing LHCb experiment. In particular we predict that a clean peak should be seen for a hidden charm resonance that couples to the ηcp channel in the invariant ηcp mass distribution.