Abstract
The existence of charged Higgs boson(s) is inevitable in models with two (or more) Higgs doublets. Hence, their discovery would constitute unambiguous evidence for new physics beyond the Standard Model (SM). Taking into account all relevant results from direct charged and neutral Higgs boson searches at LEP and the LHC, as well as the most recent constraints from flavour physics, we present a detailed analysis of the current phenomenological status of the charged Higgs sector in a variety of well-motivated two Higgs doublet models (2HDMs). We find that charged Higgs bosons as light as 75~mathrm {GeV} can still be compatible with the combined data, although this implies severely suppressed charged Higgs couplings to all fermions. In more popular models, e.g. the 2HDM of Type II, we find that flavour physics observables impose a combined lower limit on the charged Higgs mass of M_{H^pm } gtrsim 600 GeV – independent of tan beta – which increases to M_{H^pm } gtrsim 650 GeV for tan beta < 1. We furthermore find that in certain scenarios, the signature of a charged Higgs boson decaying into a lighter neutral Higgs boson and a W boson provides a promising experimental avenue that would greatly complement the existing LHC search programme for charged Higgs boson(s).
Highlights
A well motivated class of models, compatible with the Higgs discovery, is given by extending the Standard Model (SM) Higgs sector by a second scalar SU(2)L doublet, the so-called Two Higgs Doublet Model (2HDM)
We discuss the constraints from direct searches for charged Higgs bosons at the Large Hadron Collider (LHC), as well as the indirect constraints on the charged Higgs sector that can be inferred from LHC searches for neutral Higgs bosons, given certain model assumptions
We considered constraints from Higgs searches at LEP and the LHC, measurements of the 125 GeV Higgs signal rates, and limits from flavour physics observables
Summary
A well motivated class of models, compatible with the Higgs discovery, is given by extending the SM Higgs sector by a second scalar SU(2)L doublet, the so-called Two Higgs Doublet Model (2HDM). It is possible to relax the Z2-symmetry, and consider generic Yukawa couplings, such that the λF matrix elements are free parameters In such a case, the charged Higgs couplings to fermions read: λUi j λiDj 1. Combining data of the four LEP experiments from searches in the τ ν and cs final states, a limit of MH± 80 GeV (still mildly dependent on the branching ratio BR(H ± → τ ν)) is obtained under the assumption that the decay H ± → W ±h, with a light neutral Higgs boson h, is absent [64].1. In the 2HDM scenario with a general Yukawa structure (scenario (f), see Sect. 4), we neglect the interference contribution ∝ λtt λbb, and use only the contribution that is dominating, i.e. the cross section term ∝ λ2tt (∝ λ2bb) if mt λtt > mbλbb (mt λtt < mbλbb)
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