ATLAS discovery potential for a heavy charged Higgs boson

The sensitivity of the ATLAS detector to the discovery of a heavy charged Higgs boson is presented. Assuming a heavy SUSY spectrum, the most promising channels above the top quark mass are $H^{\pm }\to tb$ and $H^{\pm }\to {\tau }^{\pm }{\nu }_{\tau }$ which provide coverage in the low and high $\tan \beta$ regions up to $\sim 600$ GeV. The achievable precisions on the charged Higgs mass and $\tan \beta$ determination are also discussed. The $H^{\pm }\to W^{\pm }{h}^0$ channel, though restricted to a small MSSM parameter space, shows a viable signal in NMSSM where the parameter space is less constrained. The observation of the channel $H^{-}\to {\tau }_L^{-}{\nu }_{\tau }+c\mathrm{.}c\mathrm{.}$ may constitute a distinctive evidence for models with singlet neutrinos in large extra dimensions.