Search for charged Higgs bosons in e+e− collisions at = 181–184 GeV

Abstract Data collected at centre-of-mass energies of 181–184 GeV by ALEPH at LEP , corresponding to an integrated luminosity of 56.9 pb −1 , are analysed in a search for pair-produced charged Higgs bosons H ± . Three analyses are employed to select the τ + ν τ τ − ν τ , c s τ − ν τ / c s τ + ν τ and c s s c final states. No evidence for a signal is found. Mass limits are set as a function of the branching fraction B(H + → τ + ν τ ). Under the assumption that the decay modes considered cover the totality of the possible final states, charged Higgs bosons with masses below 59 GeV/ c 2 are excluded at 95% C.L. independently of B(H + → τ + ν τ ).