Search for Charged Higgs Bosons in e+e- Collisions at sqrts(s) = 189-209 GeV

TL;DR

This paper reports a search for charged Higgs bosons in electron-positron collisions at energies between 189 and 209 GeV, setting new limits on their mass and decay properties based on OPAL experiment data.

Contribution

It provides the first comprehensive search for charged Higgs bosons at these energies, deriving model-independent limits and exploring parameter spaces of 2HDM models.

Findings

No signal observed for charged Higgs bosons.

Excluded charged Higgs bosons up to 76.3 GeV at 95% confidence level.

Set limits on Higgs-boson masses in 2HDM models.

Abstract

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 sqrt(s)=189-209 GeV, corresponding to an integrated luminosity of approximately 600 pb-1. Charged Higgs bosons are assumed to be pair-produced and to decay into q qbar, tau nu or A W+-. 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 BR(H+- -> tau nu) + BR(H+- -> qq)=1, motivated by general 2HDM type II models, excluded areas on the [m(H+-), BR(H+- -> tau nu)] 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+- -> tau nu). A scan of the 2HDM type I model parameter space is performed and limits on the Higgs-boson masses m(H+-) and m(A) are presented for different choices of tan(beta).