  A search is presented for new particles in an extension to the Standard Model
that includes a heavy Higgs boson H0, an intermediate charged Higgs boson pair
H+-, and a light Higgs boson h0. The analysis searches for events involving the
production of a single heavy neutral Higgs boson which decays to the charged
Higgs boson and a W boson, where the charged Higgs boson subsequently decays
into a W boson and the lightest neutral Higgs boson decaying to a
bottom--antibottom-quark pair. Such a cascade results in a W-boson pair and a
bottom--antibottom-quark pair in the final state. Events with exactly one
lepton, missing transverse momentum, and at least four jets are selected from a
data sample corresponding to an integrated luminosity of 20.3/fb, collected by
the ATLAS detector in proton--proton collisions at sort(s)=8 TeV at the LHC.
The data are found to be consistent with Standard Model predictions, and 95%
confidence-level upper limits are set on the product of cross section and
branching ratio. These limits range from 0.065 pb to 43 pb as a function of H0
and H+- masses, with m(h0) fixed at 125 GeV.
