An Investigation of Charged Higgs Phenomenology in 3HDM and its CP-violation Anomalies

Abstract

In this thesis, we focus on the 3-Higgs-Doublets-Model (3HDM) with 3 active Higgs doublets and study some of the features of its extended scalar structure. Specifically, we investigate the phenomenology of the charged Higgs boson sector at both lepton and hadron colliders as well as in low energy experiments. By using LHC and LEP2 data, we study the properties of a CP-conserving light charged Higgs boson in its H^±₂ → cb decay channel. In order to detect this signature, we discuss the benefit of improved flavour tagging at both LEP2 and the LHC. In addition, we study three testable CP-violating asymmetry observables at the LHC and B factories, which could constrain the Yukawa couplings in the 3HDM when these are assumed complex only in the charged Higgs boson sector. Of particular interest is the untagged-asymmetry ACP(B¯ → Xs+dγ), a measurement of which at 2.5% or more could produce 5σ evidence for new physics that can be accommodated in such a 3HDM. Moreover, we evaluate the constraints on the charged Higgs boson sector from both BR(B¯ → Xsγ) and electron/neutron electric dipole moments (e/nEDMs), again, by assuming only a single CP-violating phase in the charged Higgs boson sector. In such a context, we illustrate a special GIM type cancellation mechanism entering the e/nEDMs, which is exact when the two physical charged Higgs bosons of the 3HDM (H^±₂and H^±₃) are strictly degenerate in mass but still enables interesting and viable new phenomenology with a mass difference up to the Electroweak (EW) scale

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ORCID for Stefano Moretti: orcid.org/0000-0002-8601-7246

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