Search for charged Higgs bosons in a+e- collisions at energies up to √s=209 GeV

A search for charged Higgs bosons produced in pairs is performed with data collected at centre-of-mass energies ranging from 189 to 209 GeV by ALEPH at LEP, corresponding to a total luminosity of 629 pb(-1). The three final states tau(+)nu(tau)tau(-)(nu) over bar (tau), c (s) over bar tau- (nu) over bar (tau) and c (s) over bars (c) over bar are considered. No evidence for a signal is found and lower limits are set on the mass m(H)+/- as a function of the branching fraction B(H+ --> tau(+)nu(tau)). In the framework of a two-Higgs-doublet model, and assuming B(H+ --> tau(+)nu(tau)) + B(H+ --> c (s) over bar) = 1, charged Higgs bosons with masses below 79.3 GeV/c(2) are excluded at 95% confidence level independently of the branching ratios. (C) 2002 Elsevier Science B.V. All rights reserved.