Search for charged Higgs bosons in e+e− collisions at $\sqrt{s}=189\mbox{--}209\ \mbox{GeV}$

A search is made for charged Higgs bosons predicted by Two-Higgs-Doublet extensions of the Standard Model (2HDM) using electron-positron collision data collected by the OPAL experiment at [Formula: see text], corresponding to an integrated luminosity of approximately 600 pb^-1. Charged Higgs bosons are assumed to be pair-produced and to decay into [Formula: see text], <i>τν</i>_<i>τ</i> or AW^±. No signal is observed. Model-independent limits on the charged Higgs-boson production cross section are derived by combining these results with previous searches at lower energies. Under the assumption [Formula: see text], motivated by general 2HDM type II models, excluded areas on the [Formula: see text] plane are presented and charged Higgs bosons are excluded up to a mass of 76.3 GeV at 95 % confidence level, independent of the branching ratio BR(H^±→<i>τν</i>_<i>τ</i> ). A scan of the 2HDM type I model parameter space is performed and limits on the Higgs-boson masses [Formula: see text] and <i>m</i>_A are presented for different choices of tan<i>β</i>.