Studies of B${}_{\mathrm{s}2}^{\ast }(5840{)}^0$ and B${}_{\mathrm{s}1}(5830{)}^0$ mesons including the observation of the B${}_{\mathrm{s}2}^{\ast }(5840{)}^0\to$ B${}^0$K${}_{\mathrm{S}}^0$ decay in proton-proton collisions at $\sqrt{s}=$ 8 TeV

Measurements of ${\mathrm{B}}_{\mathrm{s}2}^{\ast }(5840{)}^0$ and ${\mathrm{B}}_{\mathrm{s}1}(5830{)}^0$ mesons are performed using a data sample of proton-proton collisions corresponding to an integrated luminosity of 19.6 fb${}^{-1}$, collected with the CMS detector at the LHC at a centre-of-mass energy of 8 TeV. The analysis studies $P$-wave ${\mathrm{B}}_{\mathrm{S}}^0$ meson decays into ${\mathrm{B}}^{(\ast )+}{\mathrm{K}}^{-}$ and ${\mathrm{B}}^{(\ast )0}{\mathrm{K}}_{\mathrm{S}}^0$, where the ${\mathrm{B}}^{+}$ and ${\mathrm{B}}^0$ mesons are identified using the decays ${\mathrm{B}}^{+}\to \mathrm{J}\mathrm{/}\psi {\mathrm{K}}^{+}$ and ${\mathrm{B}}^0\to \mathrm{J}\mathrm{/}\psi {\mathrm{K}}^{\ast }(892{)}^0$. The masses of the $P$-wave ${\mathrm{B}}_{\mathrm{S}}^0$ meson states are measured and the natural width of the ${\mathrm{B}}_{\mathrm{s}2}^{\ast }(5840{)}^0$ state is determined. The first measurement of the mass difference between the charged and neutral ${\mathrm{B}}^{\ast }$ mesons is also presented. The ${\mathrm{B}}_{\mathrm{s}2}^{\ast }(5840{)}^0$ decay to ${\mathrm{B}}^0{\mathrm{K}}_{\mathrm{S}}^0$ is observed, together with a measurement of its branching fraction relative to the ${\mathrm{B}}_{\mathrm{s}2}^{\ast }(5840{)}^0\to {\mathrm{B}}^{+}{\mathrm{K}}^{-}$ decay.