Pentaquarks in semileptonic Λb decays

In terms of Pc1,c2=Pc(4380,4450)+ as the hidden charm pentaquark states to consist of cc̄uud, we study the semileptonic Λb→(Pc1,c2→)J∕ψpℓ−ν̄ℓ decays. In our discussion, while the main contribution to Λb→K−J∕ψp is from the non-perturbative process via the doubly charmful b→cc̄s transition, we propose that the Λb→Pc1,c2→J∕ψp transitions partly contribute to the Λb→K−(Pc1,c2→)J∕ψp decays, in which the required cc̄ pair is formed by the sea quarks, intrinsic charm, or both. We predict that B(Λb→J∕ψpℓ−ν̄ℓ)=(2.04−1.57+4.82,1.75−1.35+4.14)×10−6 for ℓ=(e,μ), which are about two orders of magnitude smaller than the observed decay of Λb→pμν̄μ. We also explore the angular correlations for the J∕ψp and ℓ−ν̄ℓ pairs. Our results of the decay branching ratios and angular asymmetries in Λb→J∕ψpℓ−ν̄ℓ, accessible to the ongoing experiments at the LHCb, can be used to improve the understanding of the hidden charm pentaquark states.