Measurement of the shape of the Λ⁰_b → Λ⁺_c µ⁻ν_µ differential decay rate

A measurement of the shape of the differential decay rate and the associated Isgur-Wise function for the decay Λ⁰_b → Λ⁺_c µ⁻ν_µ is reported, using data corresponding to 3 fb⁻¹ collected with the LHCb detector in proton-proton collisions. The Λ⁺_c µ⁻ν_µ(+ anything) final states are reconstructed through the detection of a muon and a Λ⁺_c baryon decaying into pK⁻π⁺, and the decays Λ⁰_b → Λ⁺_c π⁺π⁻µ⁻ν_µ are used to determine contributions from Λ⁰_b → Λ^∗_c⁺ µ⁻ν_µ decays. The measured dependence of the differential decay rate upon the squared four-momentum transfer between the heavy baryons, q², is compared with expectations from heavy-quark effective theory and from unquenched lattice QCD predictions.