Heavy Higgs Bosons at the LHC Upgrade

We evaluate the discovery potential for the heavy Higgs bosons at the LHC energy upgrade with $\sqrt{s}=27$ TeV. We take degenerate mass spectrum and assume near the alignment limit in the Type-II Two Higgs Doublet Model for illustration. We explore the observability of the heavy neutral Higgs bosons by examining the leading decay channel $H^0\mathrm{/}{A}^0\to {\tau }^{+}{\tau }^{-}$ and the clean signals from $H^0\to W^{+}{W}^{-},ZZ$ via gluon-gluon fusion production. The associated production of a top quark and a charged Higgs boson via $gb\to t H^\pm$ is adopted to predict the discovery potential of heavy charged Higgses. We also emphasize the potential importance of the electroweak production of Higgs boson pairs, i.e. $pp\to W^{\ast }\to H^{\pm }{A}^0$ and $pp\to Z^\ast/\gamma^\ast \to H^+ H^-$. They are only governed by pure electroweak gauge couplings and can provide complementary information to the conventional signals in the determination of the nature of the Higgs sector.