  Charged Higgs boson may be produced at hadron colliders via the decay of top
quarks. At the LHC, The large production cross section of top quarks pairs will
make it one of the earliest channels allowing to search for physics beyond the
standard model. Assuming the decay $H^+ \to \tau^+\nu$, previous searches have
so far considered only hadronic tau decays. Here we show that by using
appropriate kinematical variables (transverse mass observables), leptonic tau
decays can be used as well, for both observing and possibly measuring the mass
of the charged Higgs boson. This can increase the overall experimental
sensitivity to charged Higgs bosons at hadron colliders.
