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

Upper limits on the cross-section of the pair-production process e(+)e(-) -> h(0)A(0), assuming 100 % branching fraction to hadrons, are derived from a new search for the h(0)A(0) -> hadrons final state, independently of the hadronic flavour of the decay products. This study, combined with previously published searches for the neutral Higgs bosons h(0) and A(0), is used to constrain the Type II Two Higgs Doublet Model (2HDM(II)) with no CP violation in the Higgs sector and no additional non-Standard Model particles besides the five Higgs bosons. The analysis combines LEP1 and LEP2 data collected with the OPAL detector up to the highest available centre-of-mass energies. The searches are sensitive to the h(0), A(0) -> q (q) over bar, gg, tau(+)tau(-) and h(0) -> A(0)A(0) 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 (m(h), m(A)), (m(h), tan beta) and (m(A), tan beta) planes, using both direct neutral Higgs boson searches and indirect limits derived from Standard Model high precision measurements. The region 1 less than or similar to m(h) less than or similar to 55 GeV and 3 less than or similar to m(A) less than or similar to 63 GeV is excluded at 95 % CL, independently of m(h), m(A), tan beta and for selected values of alpha which are representative of a complete alpha-scan.