Determination of the quark coupling strength /V_ub/ using baryonic decays

In the Standard Model of particle physics, the strength of the couplings of the b quark to the u and c quarks, /V_ub/ and /V_cb/, are governed by the coupling of the quarks to the Higgs boson. Using data from the LHCb experiment at the Large Hadron Collider, the probability for the Λ_b ⁰ baryon to decay into the pμ^-v_μ final state relative to the Λ_c ⁺μ^-v_μ final state is measured. Combined with theoretical calculations of the strong interaction and a previously measured value of /V_cb/, the first /V_ub/ measurement to use a baryonic decay is performed. This measurement is consistent with previous determinations of /V_ub/ using B meson decays to specific final states and confirms the existing incompatibility with those using an inclusive sample of final states.