Search for charged Higgs bosons in e+e- collisions at energies up to sqrt(s) = 189GeV

TL;DR

This study searches for charged Higgs bosons in electron-positron collisions at energies up to 189 GeV, setting mass limits and excluding certain models based on the absence of observed signals.

Contribution

First search at LEP energies for pair-produced charged Higgs bosons, providing new mass exclusion limits and decay mode constraints.

Findings

Charged Higgs bosons with masses below 65.4 GeV/c2 are excluded at 95% confidence level.

No evidence of charged Higgs boson production was observed in the analyzed data.

Upper limits on production cross sections were established as a function of branching ratios.

Abstract

The data collected at centre-of-mass energies of 188.6 GeV by ALEPH at LEP, corresponding to an integrated luminosity of 176.2 pb-1, are analysed in a search for pair-produced charged Higgs bosons H+/-. Three analyses are employed to select the taunutaunu, taunucs and cscs final states. No evidence for a signal is found. Upper limits are set on the production cross section as a function of the branching fraction BR(H+ to tau nu) and of the mass M(H+), assuming that the sum of the branching ratios is equal to one. In the framework of a two-Higgs-doublet model, charged Higgs bosons with masses below 65.4 GeV/c2 are excluded at 95% confidence level independently of the decay mode.