Abstract
The Standard Model (SM) is amended by one generation of quarks and leptons which are vector-like (VL) under the SM gauge group but chiral with respect to a new $\mathrm{U}(1)_{3-4}$ gauge symmetry. We show that this model can simultaneously explain the deviation of the muon $g-2$ as well as the observed anomalies in $b\rightarrow s\mu^+\mu^-$ transitions without conflicting with the data on Higgs decays, lepton flavor violation, or $B_s-\bar{B}_s$ mixing. The model is string theory motivated and GUT compatible, i.e. UV complete, and fits the data predicting VL quarks, leptons and a massive $Z'$ at the $\mathrm{TeV}$ scale, as well as $\tau\to3\mu$ and $\tau\to\mu\gamma$ within reach of future experiments. The Higgs couplings to SM generations are automatically aligned in flavor space.
Highlights
The Standard Model (SM) is a highly successful theory in predicting and fitting many experimental measurements, with few exceptions
We find that the model can simultaneously fit the observed quark and lepton masses, as well as the ðg − 2Þμ and b → sμþμ− anomalies without violating bounds from electroweak precision observables, lepton flavor violating (LFV) decays, or Bs − Bs mixing
We have studied the Standard Model extended by one complete family of “VL” fermions, including right-handed neutrinos, which are vectorlike with respect to the Standard
Summary
The Standard Model (SM) is a highly successful theory in predicting and fitting many experimental measurements, with few exceptions. It has been shown that combining an additional Z0, VL leptons, and VL quarks one can successfully address both the muon g − 2 and the anomalous B physics observables simultaneously [33,34,35] These models predict significant deviations of the SM in h → μμ [28,29] and h → μτ [31,34] and have an upper bound on the Z0 mass by keeping Bs − Bs oscillations close to their SM value [30]. The first and second families are distinguished by the direction of the D4 breaking VEV hφai 1⁄4 δa2vφ We assume this alignment to happen at a high-scale M (one should imagine M ∼ Mstring or M ∼ MGUT), and the corresponding effective operator coefficient, should be imagined as vφ ≡ hΦihφ2i=M where Φis a SM and Uð1Þ3−4 neutral scalar that gets a VEV around the weak scale. A more detailed analysis should include all three families and their flavor physics, but that is beyond the scope of the present paper
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