Searching for a light Higgs boson

The Linde-Weinberg bound on the mass of the Higgs boson does not apply if one of the fermions of the standard model is very massive or in non-standard models with multiple Higgs particles. We consider both the standard model and a common extension thereof to two or more Higgs doublets. If the Higgs responsible for lepton masses is very light, one reliable method for indirectly detecting it would be a more careful measurement of g-2 for the muon. More direct is the search for Higgs particles detected in association with τ pairs in existing or defunct e+e- colliders operating well below the Z mass. We analyze both methods in detail, and find that data from several existing colliders could eliminate large portions of parameter space - or, perhaps, find the Higgs boson. (orig.)