Abstract
We investigate the phenomenology of the charged Higgs boson at the International Linear Collider (ILC) within the framework of the type-X Two-Higgs Doublet Model, where a light charged Higgs boson, with a mass around 200 GeV or even smaller than top quark mass, is still being consistent with flavor physics data as well as with collider experimental data. In the theoretically and experimentally allowed parameter space, the e(+)e(-) -> (HWS)-W-+/--S--/+ (with S = H, A) production processes can yield signatures with event rates larger than those from e(+)e(-) -> H+H- and offer sensitivity to the Higgs mixing parameter sin(beta - alpha). We consider the bosonic H-+/- -> (WS)-S-+/- decays, where the neutral scalar S further decays into a pair of tau leptons. We show, through a detector-level Monte Carlo analysis, that the resulting [tau tau][tau tau]WW final state could be seen at the ILC with at least 500 GeV center-of-mass energy and 500 fb(-1) of luminosity.