  A search is performed for a spin-0 boson, $\phi$, produced in proton-proton
collisions at centre-of-mass energies of 7 and 8 TeV, using prompt
$\phi\rightarrow\mu^+\mu^-$ decays and a data sample corresponding to an
integrated luminosity of approximately 3.0 ${\rm fb}^{-1}$ collected with the
LHCb detector. No evidence is found for a signal in the mass range from 5.5 to
15 GeV. Upper limits are placed on the product of the production cross-section
and the branching fraction into the dimuon final state. The limits are
comparable to the best existing over most of the mass region considered and are
the first to be set near the $\Upsilon$ resonances.
