Abstract
In the context of two-Higgs doublet models, we explore the possibility of searching for heavy Higgs bosons in the toverline{t}Z and tbW final states. We develop realistic analysis strategies and in the case of the toverline{t}Z channel provide a detailed evaluation of the new-physics reach at the 14 TeV LHC. We find that already with an integrated luminosity of 300 fb−1 searches for the toverline{t}Z signature can provide statistically significant constraints at low values of tan β for heavy Higgs masses in the range from around 450 GeV to 1150 GeV. Future searches for heavy Higgses in the tbW final state are also expected to be able to probe parts of this parameter space, though the precise constraints turn out to depend sensitively on the assumed systematics on the shape of the toverline{t} background.
Highlights
All the channels mentioned so far have in common that they only have limited sensitivity to additional Higgses with masses above the top threshold, in particular if the H/A → ttbranching ratio is sizeable as it happens to be the case in the minimal supersymmetric SM (MSSM) at low and moderate tan β
We identify the 125 GeV resonance discovered at the LHC with the h field, denote the angle that mixes the neutral CP-even states by α, and define tan β to be the ratio of the Higgs vacuum expectation values (VEVs)
Since the size of the signal-background interference typically exceeds the statistical uncertainties expected in future LHC runs, a rigorous assessment of the prospects of the tbW final state to search for heavy Higgses should be based on Monte Carlo (MC) simulations that include interference effects between the new-physics signal and the SM background
Summary
The addition of the second Higgs doublet in 2HDMs leads to five physical spin-0 states: two neutral CP-even ones (h and H), one neutral CP-odd state (A), and the remaining two carry electric charge of ±1 and are degenerate in mass (H±). In the limit cβ−α → 0 and MH± > MH > v, Mh with v 246 GeV the Higgs VEV and assuming that the quartic couplings λi that appear in the scalar potential are of order 1, the gHhh coupling behaves approximately as gHhh ∝ cβ−α MH2 ±/v It follows that for a sufficiently large mass splitting MH± − MH > 0, the partial decay width Γ (H → hh) ∝ gH2 hh/MH can be numerically relevant in pure 2HDMs. In contrast, in the MSSM the trilinear Hhh coupling scales as gHhh ∝ MZ2 /v s4β in the limit α → β − π/2. One observes that for such parameter choices besides H → ttand H → AZ (A → ttand A → HZ) the channel H → H±W ∓ (A → H±W ∓) is important at high MH (MA) This feature is expected because H (A) decays to a charged Higgs and a W boson are kinematically allowed if MH > MH± + MW (MA > MH± + MW ) and unsuppressed in the alignment limit see (2.2).
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