Signals of top quarks with charged-Higgs-boson decay atpp¯colliders

If the top quark decays dominantly via a charged Higgs boson $t\to b{H}^{+}$, as occurs if $m_t<M_W+m_b$ and $m_{H^{\pm }}<m_t-m_b$, the conventional top-quark signals at $p\overline{p}$ colliders (based on $t\to b{W}^{*}$ charged-current decays) are suppressed. Distinctive new signals appear, based on $H^{+}\to \overline{\tau }\nu$ decays; they include events with large missing $p_T$, events with isolated $\tau$ jets or leptons plus hadronic jets, and events with two isolated $\tau$ jets. We calculate typical cross sections and distributions for the Fermilab Tevatron $p\overline{p}$ collider; the results are sensitive to the $H\to \tau \nu$ branching fraction, that may well be large.