Bottomonium Spectroscopy with Mixing of eta{sub b} States and a Light CP-Odd Higgs Boson

The mass of the eta{sub b}(1S), measured recently by the BABAR Collaboration, is significantly lower than expected from QCD predictions for the UPSILON(1S)-eta{sub b}(1S) hyperfine splitting. We suggest that the observed eta{sub b}(1S) mass is shifted downwards due to a mixing with a CP-odd Higgs boson A with a mass m{sub A} in the range 9.4-10.5 GeV compatible with LEP, CLEO, and BABAR constraints. We determine the resulting predictions for the spectrum of the eta{sub b}(nS)-A system and the branching ratios into tau{sup +}tau{sup -} as functions of m{sub A}.