Muon $g-2$ and CKM Unitarity in Extra Lepton Models

We investigate the impact of extra leptons on observed tensions in the muon $g-2$ and the first-row CKM unitarity. By introducing a new SU(2)${}_L$ doublet lepton and a SU(2)${}_L$ triplet lepton, we find that both of the tensions can be explained simultaneously under constraints from electroweak precision observables and Higgs-boson decays. Our model could be tested by measurements of $h\to \mu \mu$ at future collider experiments.