Abstract
The invisible variant axion model is very attractive as it is free from the domain wall problem. This model requires two Higgs doublets at the electroweak scale where one Higgs doublet carries a nonzero Peccei-Quinn (PQ) charge and the other is neutral under the PQ U(1) symmetry. We consider the most interesting and less constrained scenario of the variant axion model, where only the right-handed top quark is charged under the PQ symmetry and couples with the PQ-charged Higgs doublet. As a result, the top quark can decay to the observed standard-model-like Higgs boson h and the charm or up quark, t ! h c=u, which is testable soon at the LHC Run-II. Moreover, we propose a method to probe the chiral nature of the Higgs avor-changing interaction using the angular distribution of t! ch decays if a sucient number of such events are observed. We also show that our model has the capacity to explain the h ! decay reported by the CMS Collaboration, if the right-handed tau lepton also carries a PQ charge and couples to the PQ-charged Higgs boson.
Highlights
(FCNC) couplings1 of the Higgs bosons to at least quarks
We propose a method to probe the chiral nature of the Higgs flavor-changing interaction using the angular distribution of t → ch decays if a sufficient number of such events are observed
We show that our model has the capacity to explain the h → τ μ decay reported by the CMS collaboration, if the right-handed tau lepton carries a PQ charge and couples to the PQ-charged Higgs boson
Summary
As a minimal setup of the variant axion model, we introduce two Higgs doublet fields Φ1 and Φ2 and a scalar field σ with PQ charges 0, −1 and 1, respectively. Note that in the second term of eq (2.10), the (tan β + cot β)Hu part describes the mixing among up-type quarks and Yudiag controls the strength of coupling with the dominant component given by the top Yukawa coupling. It should be emphasized that LFCNC in eq (2.13) contains FCNC terms, and flavor-diagonal Yukawa interactions so that the corresponding up-type quark Yukawa couplings get modified from those in eq (2.12) with nonvanishing a and Hu. Obviously, the flavor-violating effects vanish in the limit of cos(β − α) = 0. Where H is the counterpart of Hu. where H is the counterpart of Hu This Lagrangian describes lepton flavor violation with the chirality asymmetry as in the up-type quark sector.
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