Observation of the Bs0→X(3872)ϕ Decay

Using a data sample of proton-proton collisions at $\sqrt{s}=13\text{ }\text{ }\mathrm{TeV}$, corresponding to an integrated luminosity of $140\text{ }\text{ }{\mathrm{fb}}^{\ensuremath{-}1}$ collected by the CMS experiment in 2016--2018, the ${B}_{s}^{0}\ensuremath{\rightarrow}X(3872)\ensuremath{\phi}$ decay is observed. Decays into $J/\ensuremath{\psi}{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}$ and ${K}^{+}{K}^{\ensuremath{-}}$ are used to reconstruct, respectively, the $X(3872)$ and $\ensuremath{\phi}$. The ratio of the product of branching fractions $\mathcal{B}[{B}_{s}^{0}\ensuremath{\rightarrow}X(3872)\ensuremath{\phi}]\mathcal{B}[X(3872)\ensuremath{\rightarrow}J/\ensuremath{\psi}{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}]$ to the product $\mathcal{B}[{B}_{s}^{0}\ensuremath{\rightarrow}\ensuremath{\psi}(2S)\ensuremath{\phi}]\mathcal{B}[\ensuremath{\psi}(2S)\ensuremath{\rightarrow}J/\ensuremath{\psi}{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}]$ is measured to be $[2.21\ifmmode\pm\else\textpm\fi{}0.29(\mathrm{stat})\ifmmode\pm\else\textpm\fi{}0.17(\mathrm{syst})]%$. The ratio $\mathcal{B}[{B}_{s}^{0}\ensuremath{\rightarrow}X(3872)\ensuremath{\phi}]/\mathcal{B}[{B}^{0}\ensuremath{\rightarrow}X(3872){K}^{0}]$ is found to be consistent with one, while the ratio $\mathcal{B}[{B}_{s}^{0}\ensuremath{\rightarrow}X(3872)\ensuremath{\phi}]/\mathcal{B}[{B}^{+}\ensuremath{\rightarrow}X(3872){K}^{+}]$ is two times smaller. This suggests a difference in the production dynamics of the $X(3872)$ in ${B}^{0}$ and ${B}_{s}^{0}$ meson decays compared to ${B}^{+}$. The reported observation may shed new light on the nature of the $X(3872)$ particle.

Observation of the Bs0→X(3872)ϕ Decay | Litlas