Flavour-independent h0A0 search and two Higgs doublet model interpretation of neutral Higgs boson searches at LEP

Abstract

Upper limits on the cross-section of the pair-prodn. process e+e-->h0A0, assuming 100% branching fraction to hadrons, are derived from a new search for the h0A0->hadrons final state, independently of the hadronic flavor of the decay products. This study, combined with previously published searches for the neutral Higgs bosons h0 and A0, is used to constrain the Type II Two Higgs Doublet Model (2HDM(II)) with no CP violation in the Higgs sector and no addnl. non-Std. Model particles besides the five Higgs bosons. The anal. combines LEP1 and LEP2 data collected with the OPAL detector up to the highest available center-of-mass energies. The searches are sensitive to the h0, A0->q.lovin.qq, gg, t+t- and h0->A0A0 decay modes of the Higgs bosons. A benchmark scan of the 2HDM(II) parameter space is performed. Large regions of the 2HDM(II) parameter space explored are excluded at the 95% CL in the (mh, mA), (mh, tanb) and (mA, tanb) planes, using both direct neutral Higgs boson searches and indirect limits derived from Std. Model high precision measurements. The region 1.ltorsim.?mb.ltorsim.55GeV and 3.ltorsim.mA.ltorsim.GeV is excluded at 95 % CL, independently of mA, tanb and for selected values of which are representative of a complete a-scan. [on SciFinder (R)]