The possibility of a light charged Higgs boson H ± that decays predominantly to quarks (cs and/or cb) and with a mass in the range 80 GeV ≤ m H ± ≤ 90 GeV is studied in the context of Three-Higgs-Doublet Models (3HDMs). At present the Large Hadron Collider (LHC) has little sensitivity to this scenario, and currently the best constraints are from LEP2 and Tevatron searches. The branching ratio of H ± → cb can be dominant in two of the five types of 3HDM, and we determine the parameter space where this occurs. The decay H ± → cb has recently been searched for at the LHC for the first time, and with increased integrated luminosity one would expect sensitivity to the region 80 GeV ≤ m H ± ≤ 90 GeV due to the smaller backgrounds with respect to H ± → cs decays. * Electronic address: a.g.akeroyd@soton.ac.uk † Electronic address: S.Moretti@soton.ac.uk ‡ Electronic address: ms32g13@soton.ac.uk arXiv:1810.05403v1 [hep-ph]

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We demonstrate a new type of cancellation of contributions to the electron and neutron electric dipole moments (EDMs) that occurs in three Higgs doublet models (3HDMs) when CP violation appears in the charged Higgs sector. The cancellation becomes exact when the two physical charged Higgs bosons in the model are degenerate in mass. Depending on the model parameters, degeneracies at the 10% level are however sufficient to evade current bounds on the electron and neutron EDMs. We demonstrate that viable parameter space remains with both charged Higgs bosons lighter than 500 GeV and large CP-violating phases while also satisfying theoretical constraints from perturbativity and experimental ones from $$ \overline{B} $$ B ¯ → Xsγ and direct searches.

The possibility of a light charged Higgs boson H ± that decays predominantly to cb and with a mass in the range 80 GeV ≤ M H ± ≤ 90 GeV is studied in the context of a 3-Higgs Doublet Model (3HDM). Searches for this decay at the Large Hadron Collider (LHC) do not have sensitivity to this mass region at present. It is shown that the searches for H ± at LEP2 could be supplemented by either one or two b-tags, which would enable such large branching ratios for H ± → cb to be probed in the above mass region. We comment on the possibility of this 3HDM scenario to explain a slight excess in the searches for H ± at LEP2, which is best fit by M H ± of around 90 GeV, and discuss the prospects for detecting H ± → cb decays at future e + e − colliders. * Electronic address: a.g.akeroyd@soton.ac.uk † Electronic address: S.Moretti@soton.ac.uk ‡ Electronic address: ms32g13@soton.ac.uk