Search for the decay $B^0\to \varphi {\mu }^{+}{\mu }^{-}$

A search for the decay $B^0\to \varphi {\mu }^{+}{\mu }^{-}$ is performed using proton-proton collisions at centre-of-mass energies of 7, 8, and 13 TeV collected by the LHCb experiment and corresponding to an integrated luminosity of 9 fb${}^{-1}$. No evidence for the $B^0\to \varphi {\mu }^{+}{\mu }^{-}$ decay is found and an upper limit on the branching fraction, excluding the $\varphi$ and charmonium regions in the dimuon spectrum, of $4.4\times {10}^{-3}$ at a 90$\mathrm{\%}$ credibility level, relative to that of the $B_s^0\to \varphi {\mu }^{+}{\mu }^{-}$ decay, is established. Using the measured $B_s^0\to \varphi {\mu }^{+}{\mu }^{-}$ branching fraction and assuming a phase-space model, the absolute branching fraction of the decay $B^0\to \varphi {\mu }^{+}{\mu }^{-}$ in the full $q^2$ range is determined to be less than $3.2\times {10}^{-9}$ at a 90$\mathrm{\%}$ credibility level.