Branching fraction measurements of the rare $B_s^0\to \varphi {\mu }^{+}{\mu }^{-}$ and $B_s^0\to f_2^{\mathrm{\prime }}(1525){\mu }^{+}{\mu }^{-}$ decays

The branching fraction of the rare $B_s^0\to \varphi {\mu }^{+}{\mu }^{-}$ decay is measured using data collected by the LHCb experiment at center-of-mass energies of $7$, $8$ and $13\mathrm{T}\mathrm{e}\mathrm{V}$, corresponding to integrated luminosities of $1$, $2$ and $6{\mathrm{f}\mathrm{b}}^{-1}$, respectively. The branching fraction is reported in intervals of $q^2$, the square of the dimuon invariant mass. In the $q^2$ region between $1.1$ and $6.0{\mathrm{G}\mathrm{e}\mathrm{V}}^2\text{\hspace{0.17em}⁣}\mathrm{/}{c}^4$, the measurement is found to lie $3.6$ standard deviations below a Standard Model prediction based on a combination of Light Cone Sum Rule and Lattice QCD calculations. In addition, the first observation of the rare $B^0_s\rightarrow f_2^\prime(1525)\mu^+\mu^-$ decay is reported with a statistical significance of nine standard deviations and its branching fraction is determined.