Abstract
We study possible effects of a light CP-odd Higgs boson on radiative Gamma decays in the Next-to-Minimal Supersymmetric Standard Model. Recent constraints from CLEO on radiative Gamma(1S) decays are translated into constraints on the parameter space of CP-odd Higgs boson masses and couplings, and compared to constraints from B physics and the muon anomalous magnetic moment. Possible Higgs-eta(b)(nS) mixing effects are discussed, notably in the light of the recent measurement of the eta(b)(1S) mass by Babar: The somewhat large Gamma(IS) - eta(b)(1S) hyperfine splitting could easily be explained by the presence of a CP-odd Higgs boson with a mass in the range 9.4 - 10.5 GeV. Then, tests of lepton universality in inclusive radiative Gamma decays can provide a visible signal in forthcoming experimental data.