Looking for a Light Higgs Particle at Present and Future Colliders

Present data do not rule out the light neutral Higgs particle h or A with mass below 40–50 GeV in the framework of the general 2HDM (”Model II”). The recent limits from LEP I on the parameters of the model, based on the Bjorken process Z → Zh, Higgs pair production Z → Ah and the Yukawa process Z → f f̄A (f = b quark or τ lepton) are presented. Including limits on Higgs bosons masses from LEP I data additional constraints on the allowed value of tanβ for mass below 2 GeV, can be obtained from the existing (g − 2)μ data. The improvement in the accuracy by factor 20 in the forthcoming (g−2)μ experiment E821 may lead to more stringent limits on mass of neutral Higgs boson up to 30 GeV, or even higher if the mass difference between h and A is larger than MZ . The exclusion/discovery potential ∗Contribution to QS’96 Workshop, June 1996, Minsk, Belarus