Abstract
We consider a simple extension of the Standard Model with flavor-dependent U(1)', that has been proposed to explain some of B-meson anomalies recently reported at LHCb. The U(1)' charge is chosen as a linear combination of anomaly-free B_3-L_3 and L_mu -L_tau . In this model, the flavor structure in the SM is restricted due to flavor-dependent U(1)' charges, in particular, quark mixings are induced by a small vacuum expectation value of the extra Higgs doublet. As a result, it is natural to get sizable flavor-violating Yukawa couplings of heavy Higgs bosons involving the bottom quark. In this article, we focus on the phenomenology of the Higgs sector of the model including extra Higgs doublet and singlet scalars. We impose various bounds on the extended Higgs sector from Higgs and electroweak precision data, B-meson mixings and decays as well as unitarity and stability bounds, then discuss the productions and decays of heavy Higgs bosons at the LHC.
Highlights
The observed fermion masses and mixing angles are well parametrized by the Higgs Yukawa couplings in the Standard Model (SM)
In the case with a small vacuum expectation value (VEV) of the extra Higgs doublet or small tan β, we find that the heavy Higgs bosons have sizable flavor-violating couplings to the bottom quark and reduced flavor-conserving Yukawa couplings to the top quark such that LHC searches for heavy Higgs bosons can be affected by extra or modified production and decay channels
We have considered an extra local U (1) with flavordependent couplings as a linear combination of B3 − L3 and Lμ − Lτ, that has been recently proposed to explain the B-meson anomalies
Summary
The observed fermion masses and mixing angles are well parametrized by the Higgs Yukawa couplings in the Standard Model (SM). The U (1) symmetry is taken as a linear combination of U (1)Lμ−Lτ and U (1)B3−L3 , which might be a good symmetry at low energy and originated from enhanced gauge symmetries such as in the U (1) clockwork framework [13] In this model, the quark mixings and neutrino masses/mixings require an extended Higgs sector, which has one extra Higgs doublet and multiple singlet scalars beyond the SM. We consider a simple extension of the SM with U (1) , where a new gauge boson Z couples to heavy flavors It is taken as a linear combination of U (1)Lμ−Lτ and U (1)B3−L3 with. For a set of quartic couplings for S and H1,2 that are relevant for electroweak symmetry and U (1) breaking, we have collected unitarity bounds in Appendix B, which are used to constrain the parameter space of the Higgs sector in Sect.
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