Amplitude analysis and the branching fraction measurement of $\bar{B}^0_s \to J/\psi K^+K^-$

An amplitude analysis of the final state structure in the $\overline{B}_s^0 \to J/\psi K^+K^-$ decay mode is performed using $1.0~\rm fb^{-1}$ of data collected by the LHCb experiment in 7 TeV center-of-mass energy $pp$ collisions produced by the LHC. A modified Dalitz plot analysis of the final state is performed using both the invariant mass spectra and the decay angular distributions. Resonant structures are observed in the $K^+K^-$ mass spectrum as well as a significant non-resonant S-wave contribution. The largest resonant component is the $\phi(1020)$, accompanied by $f_0(980)$, $f_2'(1525)$, and four additional resonances. The overall branching fraction is measured to be $\mathcal{B}(\overline{B}_s^0 \to J/\psi K^+K^-)=(7.70\pm0.08\pm 0.39\pm 0.60)\times 10^{-4}$, where the first uncertainty is statistical, the second systematic, and the third due to the ratio of the number of $\overline{B}_s^0$ to $B^-$ mesons produced. The mass and width of the $ f_2'(1525)$ are measured to be $1522.2\pm 2.8^{+5.3}_{-2.0}~\rm MeV$ and $84\pm 6^{+10}_{-~5}~\rm MeV$, respectively. The final state fractions of the other resonant states are also reported.