Abstract
We consider the Standard Model (SM) with the addition of a $\mathrm{U(1)^\prime}$ gauge symmetry and a complete fourth family of quarks and leptons which are vector-like with respect to the full $\mathrm{SU(3)_C}\times \mathrm{SU(2)_L} \times \mathrm{U(1)_Y}\times \mathrm{U(1)^\prime}$ gauge symmetry. The model provides a unified explanation of experimental anomalies in $(g - 2)_\mu$ as well as $b \rightarrow s \ell^+ \ell^-$ decays. We find good fits to the deviations from the SM, while at the same time fitting all other SM observables. The model includes a new $Z^\prime$ gauge boson, a $\mathrm{U(1)^\prime}$-breaking scalar, and vector-like leptons all with mass of order a few $100$ GeV. It is consistent with all currently released high energy experimental data, however, it appears imminently testable with well designed future searches. Also precision flavor experiments, especially more accurate direct determinations of CKM matrix elements, would allow to probe the best fit points.
Highlights
The Standard Model (SM) is very successful, explaining most experimental results
We propose a model with a complete fourth family of fermions which are VL under both the SM and a Uð1Þ0 gauge symmetry
We study a model with a complete VL fourth family and Uð1Þ0 gauge symmetry
Summary
There are experimental discrepancies with some SM predictions. The current experimental measurement [1,2] shows the discrepancy, Δaμ ≔ aeμxp − aSμM 1⁄4 268ð63Þð43Þ × 10−11: ð1:1Þ. Other discrepancies are reported in observables related to b → slþl− processes. The observables testing lepton flavor nonuniversality, RK and RKÃ, deviate from the SM prediction [3,4], even though the most recent data are consistent with the SM at 2.5σ [5] or have large error bars [6]. There are deviations from the SM predictions for semileptonic branching ratios [7,8,9,10] and angular distributions [11,12,13,14,15,16,17]
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