Pentaquarks from intrinsic charms in Λb decays

We study the three-body ΛbΛb decays of Λb→J/ψpMΛb→J/ψpM with M=K−M=K− and π−π−. The two new states Pc1≡Pc(4380)+Pc1≡Pc(4380)+ and Pc2≡Pc(4450)+Pc2≡Pc(4450)+ observed recently as the resonances in the J/ψpJ/ψp invariant mass spectrum of Λb→J/ψpK−Λb→J/ψpK− can be identified to consist of five quarks, uudcc¯, being consistent with the existence of the pentaquark states. We argue that, in the doubly charmful ΛbΛb decays of Λb→J/ψpK−Λb→J/ψpK− through b→cc¯s, apart from those through the non-resonant Λb→pK−Λb→pK− and resonant Λb→Λ⁎→pK−Λb→Λ⁎→pK− transitions, the third contribution with the non-factorizable effects is not the dominant part for the resonant Λb→K−Pc1,c2,Pc1,c2→J/ψpΛb→K−Pc1,c2,Pc1,c2→J/ψp processes, such that we propose that the Pc1,c2Pc1,c2 productions are mainly from the charmless ΛbΛb decays through b→u¯us, in which the cc¯ content in Pc1,c2Pc1,c2 arises from the intrinsic charms within the ΛbΛb baryon. We hence predict the observables related to the branching ratios and the direct CP violating asymmetries to be B(Λb→π−(Pc1,c2→)J/ψp)/B(Λb→K−(Pc1,c2→)J/ψp)=0.58±0.05B(Λb→π−(Pc1,c2→)J/ψp)/B(Λb→K−(Pc1,c2→)J/ψp)=0.58±0.05, ACP(Λb→π−(Pc1,c2→)J/ψp)=(−7.4±0.9)%ACP(Λb→π−(Pc1,c2→)J/ψp)=(−7.4±0.9)%, and ACP(Λb→K−(Pc1,c2→)J/ψp)=(+6.3±0.2)%ACP(Λb→K−(Pc1,c2→)J/ψp)=(+6.3±0.2)%, which can alleviate the inconsistency between the theoretical expectations from the three contributions in the doubly charmful ΛbΛb decays and the observed data.