Search for Light Higgs Boson in the Yukawa process

The Yukawa process e+e- --> f fbar h/A, where f is a tau lepton or a b quark, is used to search for light scalar or pseudoscalar Higgs bosons in the framework of general two-Higgs-doublet models. The analysis is based on the data sample collected by the ALEPH experiment at LEP at centre-of-mass energies at and around the Z peak. Since no deviation from the standard model expectations has been observed in the data, this search results in a new 95 excluded region of the (mA, tan beta) plane in any two-Higgs-doublet model.