Search for Charged Higgs Bosons in Decays of Top Quarks

We present a search for charged Higgs bosons in the mass range $80 < m_{H^{\pm}} < 155$~GeV, assuming the decay $H^{+} \rightarrow \tau^{+} \nu_\tau$ (and its charge conjugate). Using 0.9~fb$^{-1}$ of lepton+jets data collected by the D0 detector, at the Fermilab Tevatron $p\bar{p}$ collider, we find no evidence for signal, and exclude branching ratios $B(t \rightarrow H^+b)$ at $95\%$ confidence level.