Observation of the decay B¯s0→χc2K+K−$$ {\overline{B}}_s^0\to {\chi}_{c2}{K}^{+}{K}^{-} $$ in the ϕ mass region

A bstractThe B¯s0→χc2K+K−$$ {\overline{B}}_s^0\to {\chi}_{c2}{K}^{+}{K}^{-} $$ decay mode is observed and its branching fraction relative to the corresponding χc1 decay mode, in a ±15 MeV/c2 window around the ϕ mass, is found to be ℬB¯s0→χc2K+K−ℬB¯s0→χc1K+K−=17.1±3.1±0.4±0.9%,$$ \frac{\mathrm{\mathcal{B}}\left({\overline{B}}_s^0\to {\chi}_{c2}{K}^{+}{K}^{-}\right)}{\mathrm{\mathcal{B}}\left({\overline{B}}_s^0\to {\chi}_{c1}{K}^{+}{K}^{-}\right)}=\left(17.1 \pm 3.1\pm 0.4\pm 0.9\right)\%, $$ where the first uncertainty is statistical, the second systematic and the third due to the knowledge of the branching fractions of radiative χc decays. The decay mode B¯s0→χc1K+K−$$ {\overline{B}}_s^0\to {\chi}_{c1}{K}^{+}{K}^{-} $$ allows the Bs0 mass to be measured as mBs0=5366.83±0.25±0.27MeV/c2,$$ m\left({B}_s^0\right)=5366.83\pm 0.25\pm 0.27\ \mathrm{M}\mathrm{e}\mathrm{V}/{c}^2, $$ where the first uncertainty is statistical and the second systematic. A combination of this result with other LHCb determinations of the Bs0 mass is made.