Detection of heavy charged Higgs bosons at future Linear Colliders

We show how a statistically significant signal of heavy charged Higgs bosons of a general Two-Higgs Doublet Model produced in association with tau-neutrino pairs can be established at future Linear Colliders in the $H^+\to t\bar b\to 4$ jet decay channel. This signature is particularly relevant in the kinematic configuration $\sqrt s\lsim2 M_{H^\pm}$, when the pair production channel $e^+e^-\to H^-H^+$ is no longer available. Here, the initially overwhelming background, constituted by top quark pair production and decay, can vigorously be reduced thanks to a dedicated selection procedure that allows one to extract a signal in a region of several tens of GeV around $M_{H^\pm}\approx \sqrt s/2$, for $\tan\beta\gsim40$.