Observation of the $\Lambda _{b}^{0} \to J{\text{/}}\psi \Lambda \phi $ Decay in the CMS Experiment

This study is devoted to the observation of the $\Lambda _{b}^{0} \to J{\text{/}}\psi \Lambda \phi $ decay using proton-proton (pp) collision data collected at $\sqrt s = 13$ TeV by the CMS experiment at the Large Hadron Collider in 2018, which corresponds to the integrated luminosity of 60fb$^{–1}$. The branching fraction ratio $\mathcal{B}(\Lambda _{b}^{0} \to J{\text{/}}\psi \Lambda \phi ){\text{/}}\mathcal{B}(\Lambda _{b}^{0} \to \psi (2S)\Lambda )$ = $(8.26 \pm 0.90({\text{stat}}) \pm 0.68({\text{syst}}{\text{.}}) \pm 0.11(\mathcal{B})) \times {{10}^{{ - 2}}}$ was measured; the first uncertainty is statistical, the second is systematic, and the third one reflects the uncertainties in the world-average branching fractions of ϕ and $\psi (2S)$ decays to reconstructed final states.