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

Measurements of ${\mathrm {B}} ^{*{\mathrm {s}}2}(5840)^0$ 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 , collected with the CMS detector at the LHC at a centre-of-mass energy of $8\,\text {TeV}$ . The analysis studies P-wave ${\mathrm {B}} ^0_{\mathrm {s}}$ meson decays into ${\mathrm {B}} ^{(*)+} \mathrm {K} ^-$ and ${\mathrm {B}} ^{(*)0} \mathrm {K} ^0_{\mathrm {S}}$ , where the ${\mathrm {B}} ^+$ and ${\mathrm {B}} ^0$ mesons are identified using the decays ${\mathrm {B}} ^+ \rightarrow {\mathrm {J}}/\psi \mathrm {K} ^+$ and ${\mathrm {B}} ^0 \rightarrow {\mathrm {J}}/\psi \mathrm {K} ^{*}(892)^0$ . The masses of the 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. The first measurement of the mass difference between the charged and neutral ${\mathrm {B}} ^{*}$ mesons is also presented. The ${\mathrm {B}} ^{*{\mathrm {s}}2}(5840)^0$ decay to ${\mathrm {B}} ^0 \mathrm {K} ^0_{\mathrm {S}}$ is observed, together with a measurement of its branching fraction relative to the ${\mathrm {B}} ^{*{\mathrm {s}}2}(5840)^0 \rightarrow {\mathrm {B}} ^+ \mathrm {K} ^-$ decay.