  Charged Higgs bosons are predicted in variety of theoretically well-motivated
new physics models with extended Higgs sectors. In this study, we focus on a
type-II two Higgs doublet model (2HDM-II) and consider a heavy charged Higgs
with its mass ranging from 500 GeV to 1 TeV as dictated by the $b\to s\gamma$
constraints which render $M_{H^\pm}>480$ GeV. We study the dominant production
mode $H^\pm t$ associated production with $H^\pm \to W^\pm A$ being the
dominant decay channel when the pseudoscalar $A$ is considerably lighter. For
such a heavy charged Higgs, both the decay products $W^\pm$ and $A$ are
relatively boosted. In such a scenario, we apply the jet substructure analysis
of tagging the fat pseudoscalar and $W$ jets in order to eliminate the standard
model background efficiently. We perform a detailed detector simulation for the
signal and background processes at the 14 TeV LHC. We introduce various
kinematical cuts to determine the signal significance for a number of benchmark
points with charged Higgs boson mass from 500 GeV to 1 TeV in the $W^\pm A$
decay channel. Finally we perform a multivariate analysis utilizing a boosted
decision tree algorithm to optimize these significances.
