Abstract
We study the Two-Higgs-Doublet Model with the aligned Yukawa sector (A2HDM) in light of the observed excess measured in the muon anomalous magnetic moment. We take into account the existing theoretical and experimental constraints with up-to-date values and demonstrate that a phenomenologically interesting region of parameter space exists. With a detailed parameter scan, we show a much larger region of viable parameter space in this model beyond the limiting case Type X 2HDM as obtained before. It features the existence of light scalar states with masses $3$ GeV $\lesssim m_H^{} \lesssim 50$ GeV, or $\ 10$ GeV $\lesssim m_A^{} \lesssim 130$ GeV, with enhanced couplings to tau leptons. The charged Higgs boson is typically heavier, with $200$ GeV $ \lesssim m^{}_{H^+} \lesssim 630$ GeV. The surviving parameter space is forced into the CP-conserving limit by EDM constraints. Some Standard Model observables may be significantly modified, including a possible new decay mode of the SM-like Higgs boson to four taus. We comment on future measurements and direct searches for those effects at the LHC as tests of the model.
Highlights
We study the Two-Higgs-Doublet Model with the aligned Yukawa sector (A2HDM) in light of the observed excess measured in the muon anomalous magnetic moment
In this paper we focus on an interesting broader formulation, the Aligned Two Higgs Doublet Model (A2HDM) [41, 42, 44, 46,47,48,49]
We find that the A2HDM can account for the experimental value of (g − 2)μ [16]
Summary
For two SU(2)L Higgs doublets with hyper-charge one, we can redefine a theoretical basis by rotating the doublets according to a global U(2) transformation [43]. The scalar potential can be expressed using Higgs basis fields as follows:. R for the matrix M in some particular pseudo-invariant basis. The Yukawa couplings of the two Higgs doublets are aligned in that they are proportional to each other and can be simultaneously diagonalized, which ensures that flavor changing neutral currents (FCNCs) do not arise at tree level. The often studied discrete Z2 2HDMs can be understood as special cases of this model which correspond with the relations among the Ai parameters summarized in table 1 In these cases, the ratio of Yukawa couplings allows us to rotate to a basis where the symmetry is manifest and only one doublet couples to each fermion type (up, down and lepton, respectively). Details of the general CP-violating A2HDM and calculations relevant to our scan can be found in a forthcoming publication ref. [58]
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