Production rates of hidden-charm pentaquark molecules in Λb decays

The partial decay widths and production mechanism of the three pentaquark states, PψN(4312), PψN(4440), and PψN(4457), discovered by the LHCb Collaboration in 2019, are still under debate. In this work, we employ the contact-range effective field theory approach to construct the D¯(∗)ςc(∗), D¯∗Λc, D¯Λc, J/ψp, and ηcp coupled-channel interactions to dynamically generate the multiplet of hidden-charm pentaquark molecules by reproducing the masses and widths of PψN(4312), PψN(4440), and PψN(4457). Assuming that the pentaquark molecules are produced in the Λb decay via the triangle diagrams, where Λb first decays into Ds(∗)Λc, then Ds(∗) scatters into D¯(∗)K, and finally the molecules are dynamically generated by the D¯(∗)Λc interactions, we calculate the branching fractions of the decays Λb→PψNK using the effective Lagrangian approach. With the partial decay widths of these pentaquark molecules, we further estimate the branching fractions of the decays Λb→(PψN→J/ψp)K and Λb→(PψN→D¯∗Λc)K. Our results show that the pentaquark states PψN(4312), PψN(4440), and PψN(4457) as hadronic molecules can be produced in the Λb decay, and on the other hand their heavy quark spin symmetry partners are invisible in the J/ψp invariant mass distribution because of the small production rates. Our studies show that it is possible to observe some of the pentaquark states in the Λb→D¯∗ΛcK decays.