  We identify and investigate novel multi-lepton signatures of extended Higgs
sectors at the LHC in the guise of CP- and flavor-conserving two-Higgs-doublet
models (2HDMs). Rather than designing individual searches tailored to specific
2HDM signals, we employ the combination of many exclusive multi-lepton search
channels to probe the collective signal from the totality of production and
decay processes. Multi-lepton signals of 2HDMs can arise from a variety of
sources, including Standard Model-like production of the CP-even scalars, $h$
and $H$, through gluon-fusion with $h,H \to ZZ^{(*)}$, or associated production
with vector bosons or top quarks, with $h,H \to WW^{(*)}, ZZ^{(*)},\tau\tau$.
Additional sources include gluon-fusion production of the heavy CP-even scalar
with decays through the light CP-even scalar, the CP-odd scalar, $A$, or the
charged scalar, $H^\pm$, such as $H \to hh$, $H \to AA$, $H \to H^+ H^-$, $H
\to ZA$, with $A \to Zh, \tau\tau$, $H^\pm \to Wh$, and $h \to WW^*,
ZZ^*,\tau\tau$. Altogether, the combined multi-lepton signal may greatly exceed
that of the Standard Model Higgs boson and provides a sensitive probe of
extended Higgs sectors. As a proof of principle, we use a factorized mapping
procedure between model parameters and signatures to determine multi-lepton
sensitivities in four different flavor conserving 2HDM parameter spaces by
simulating the acceptance times efficiency in 20 exclusive multi-lepton
channels for 222 independent production and decay topologies that arise for
four benchmark 2HDM spectra within each parameter space. A comparison of these
sensitivities with the results of a multi-lepton search conducted by the CMS
collaboration using 5 fb$^{-1}$ of data collected from 7 TeV $pp$ collisions
yields new limits in regions of 2HDM parameter space that have not previously
been covered by other types of direct experimental searches.
