Abstract
We study an extended 2 Higgs doublet model (2HDM) in which the Standard Model (SM) Yukawa interactions are forbidden due to a global $U(1{)}^{\ensuremath{'}}$ symmetry, but may arise via mixing with vectorlike families. In this model, the hierarchical structure of Yukawa couplings of quarks and leptons in the SM arises from the heavy masses of the fourth and fifth vectorlike families. Within this model, we consider various nonstandard contributions to the electron and muon anomalous magnetic moments. We first consider the $W$ exchange at one-loop level, consistent with the $\ensuremath{\mu}\ensuremath{\rightarrow}e\ensuremath{\gamma}$ constraint, and show that it yields a negligible contribution to both electron and muon anomalous magnetic moments. We then consider Higgs scalar exchange, together with vectorlike leptons, at one-loop level and show that it is possible to have nonstandard contributions to the electron and muon anomalous magnetic moments within the $1\ensuremath{\sigma}$ constraint of certain experiments. We present some benchmark points for both the muon and the electron anomalies, together with some numerical scans around these points, which indicate the mass regions of the Higgs scalars of the 2HDM in this scenario.
Highlights
The Standard Model (SM) has made many successful predictions for the phenomenology of both quark and lepton sectors with very high accuracy
We present some benchmark points for both the muon and the electron anomalies, together with some numerical scans around these points, which indicate the mass regions of the Higgs scalars of the 2 Higgs doublet model (2HDM) in this scenario
We have proposed a model to account for the hierarchical structure of the SM Yukawa couplings
Summary
The Standard Model (SM) has made many successful predictions for the phenomenology of both quark and lepton sectors with very high accuracy. In our proposed model a spontaneously broken global Uð1Þ0 symmetry is considered instead of the Z2 symmetry and the vectorlike leptons generate one-loop level contributions to the muon and electron anomalous magnetic moments and at the same type produce the SM charged lepton masses, providing a connection of the charged lepton. In the approach followed in this paper the large third family quark and lepton Yukawa couplings are effectively generated via mixing with a vectorlike fourth family of electroweak doublet fermions, which are assumed to be relatively light, with masses around the TeV scale. It has experimental consequences, since the new vectorlike fermions can be discovered either directly, or (as in this paper) indirectly via their loop contributions This approach can account for small quark mixing angles [9], as well as large lepton mixing angles via the type Ib seesaw mechanism [11]. Appendix B includes a brief discussion of heavy scalar production at a proton-proton collider
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