Branching Fraction Measurements of the Rare $B^0_s\rightarrow\phi\mu^+\mu^-$ and $B^0_s\rightarrow f_2^\prime(1525)\mu^+\mu^-$- Decays

International audienceThe branching fraction of the rare Bs0→ϕμ+μ- decay is measured using data collected by the LHCb experiment at center-of-mass energies of 7, 8, and 13 TeV, corresponding to integrated luminosities of 1, 2, and 6 fb-1, respectively. The branching fraction is reported in intervals of q2, the square of the dimuon invariant mass. In the q2 region between 1.1 and 6.0 GeV2/c4, 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 Bs0→f2′(1525)μ+μ- decay is reported with a statistical significance of 9 standard deviations and its branching fraction is determined