We search for evidence of a light Higgs boson (A0) in the radiative decays of
the narrow Upsilon(3S) resonance: Upsilon(3S) -> gamma A0, where A0 ->
invisible or A0 -> mu+mu-. Such an object appears in extensions of the Standard
Model, where a light CP-odd Higgs boson naturally couples strongly to b-quarks.
We find no evidence for such processes in a sample of 122 million Upsilon(3S)
decays collected by the BaBar collaboration at the PEP II B-factory, and set
90% C.L. upper limits on the product of the corresponding branching fractions.
We also set a limit on the di-muon branching fraction of the recently
discovered eta_b meson.Comment: 8 pages, 4 figures. To appear in the proceedings of Les Rencontres de
Physique de la Valle'e d'Aoste held at La Thuile, Italy from 1-7 March 200
