Observation of the $\mathrm{B}^{*}_{\mathrm{s}2}(5840)^0\rightarrow\mathrm{B}^0\mathrm{K}^0_{\mathrm\scriptscriptstyle S}$ decay and studies of excited $\mathrm{B}^0_\mathrm{s}$ mesons in proton-proton collisions at $\sqrt{s}=8\,\mathrm{TeV}$

The observation of the $\mathrm{B}^{*}_{\mathrm{s}2}(5840)^0\rightarrow\mathrm{B}^0\mathrm{K}^0_{\mathrm\scriptscriptstyle S}$ decay is presented and a measurement of its relative branching fraction to the $\mathrm{B}^{*}_{\mathrm{s}2}(5840)^0\rightarrow\mathrm{B}^+\mathrm{K}^{-}$ decay using a data sample of $19.6\,\mathrm{fb}^{-1}$ collected with the CMS detector in proton-proton collision at the centre-of-mass energy $8\,\mathrm{TeV}$. The analysis is performed by studying P-wave $\mathrm{B}^{0}_\mathrm{s}$ meson decays into $\mathrm{B}^+\mathrm{K}^-$ and $\mathrm{B}^0 \mathrm{K}^0_{\mathrm\scriptscriptstyle S}$ states, where the ground-state $\mathrm{B}$ mesons are identified using the decays $\mathrm{B}^+ \rightarrow \mathrm{J}/\psi\mathrm{K}^+$ and $\mathrm{B}^0 \rightarrow \mathrm{J}/\psi\mathrm{K}^+ \pi^-$. The masses of P-wave $\mathrm{B}^0_\mathrm{s}$ meson states are measured and the natural width of the $\mathrm{B}^{*}_{\mathrm{s}2}(5840)^0$ state is determined to be $\Gamma(\mathrm{B}^{*}_{\mathrm{s}2}(5840)^0)=(1.52\pm0.34\mathrm{(stat.)}\pm0.30\mathrm{(syst.)})\,\mathrm{MeV}$. The first measurement of the mass difference between the charged and neutral $\mathrm{B}^*$ mesons is also presented.