Search for the decay B 0 → ϕμ + μ −

A search for the decay B0 → φμ+μ− is performed using proton-proton colli- sions at centre-of-mass energies of 7, 8, and 13 TeV collected by the LHCb experiment and corresponding to an integrated luminosity of 9fb−1. No evidence for the B0 → φμ+μ− decay is found and an upper limit on the branching fraction, excluding the φ and char- monium regions in the dimuon spectrum, of 4.4 × 10−3 at a 90% credibility level, relative to that of the Bs0 → φμ+μ− decay, is established. Using the measured Bs0 → φμ+μ− branching fraction and assuming a phase-space model, the absolute branching fraction of the decay B0 → φμ+μ− in the full q2 range is determined to be less than 3.2 × 10−9 at a 90% credibility level.