  Many models of physics beyond Standard Model predict the existence of light
Higgs states, dark photons, and new gauge bosons mediating interactions between
dark sectors and the Standard Model. Using a full data sample collected with
the BABAR detector at the PEP-II $e^+e^-$ collider, we report searches for a
light non-Standard Model Higgs boson, dark photon, and a new muonic dark force
mediated by a gauge boson ($Z'$) coupling only to the second and third lepton
families. Our results significantly improve upon the current bounds and further
constrain the remaining region of the allowed parameter space.
