The branching fraction of the rare decay $\Lambda_{ b}^{ 0}\to \Lambda(1520) \mu^{ +}\mu^{ -}$ is measured for the first time, in the squared dimuon mass intervals, $q^2$, excluding the $J/\psi$ and $\psi(2S)$ regions. The data sample analyzed was collected by the LHCb experiment at center-of-mass energies of 7, 8, and 13 TeV, corresponding to a total integrated luminosity of $9\ \mathrm{ fb}^{ -1}$. The result in the highest $q^{ 2}$ interval, $q^{ 2} >15.0\ \mathrm{ GeV}^2/c^4$, where theoretical predictions have the smallest model dependence, agrees with the predictions.
Categories: hep-ex