Abstract
We search for evidence of a light scalar boson in the radiative decays of the Upsilon(2S) and Upsilon(3S) resonances: Upsilon(2S,3S)->gamma A(0), A(0)->mu(+)mu(-). Such a particle 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 the mass range 0.212 < m(A)(0)< 9.3 GeV in the samples of 99x10(6) Upsilon(2S) and 122x10(6) Upsilon(3S) decays collected by the BABAR detector at the SLAC PEP-II B factory and set stringent upper limits on the effective coupling of the b quark to the A(0). We also limit the dimuon branching fraction of the eta(b) meson: B(eta(b)->mu(+)mu(-))< 0.9% at 90% confidence level.