Measurement of the shape of the $\Lambda^0_b \to \Lambda^+_c\mu^-\overline{ν}_{\mu}$ differential decay rate

Abstract

A measurement of the shape of the differential decay rate and the associated Isgur-Wise function for the decay $\Lambda^0_b \to \Lambda^+_c\mu^-\overline{ν}_{\mu}$ is reported, using data corresponding to 3 fb$^{−1}$ collected with the LHCb detector in proton-proton collisions. The $\Lambda^+_c \mu^-\overline{ν}_{\mu} (+ anything)$ final states are reconstructed through the detection of a muon and a $\Lambda^+_c$ baryon decaying into $pK^-\pi^+$, and the decays $\Lambda^0_b \to \Lambda^+_c\pi^+\pi^-\mu^-\overline{ν}_{\mu}$ are used to determine contributions from $\Lambda^0_b \to \Lambda^{*+}_c\mu^-\overline{ν}_{\mu}$ decays. The measured dependence of the differential decay rate upon the squared four-momentum transfer between the heavy baryons, $q^2$, is compared with expectations from heavy-quark effective theory and from unquenched lattice QCD predictions.