Search for charged Higgs bosons in e^+e- collisions at sqrt{s} = 130 -   172 GeV
  A search is described to detect charged Higgs bosons via the process e^+e^- -> H^+H^-, using data collected by the OPAL detector at center-of-mass energies of 130-172 GeV with a total integrated luminosity of 25 pb^-1. The decay channels are assumed to be H^+ -> qq'(bar) and H^+ -> \tau^+ \nu_{\tau}. No evidence for charged Higgs boson production is observed. The lower limit for its mass is determined to be 52 GeV at 95% confidence level, independent of the H^+ -> \tau^+ \nu_{\tau} branching ratio. 
The OPAL Collaboration, K. Ackerstaff et al