Abstract
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 → μμ at future collider experiments.
Highlights
JHEP08(2020)004 the superallowed 0+ → 0+ nuclear β decays [10,11,12]
We investigate the impact of extra leptons on observed tensions in the muon g − 2 and the first-row CKM unitarity
After decoupling the extra leptons, whose masses are typically given by the vectorlike mass Mi, they contribute to low-energy observables through higher dimensional operators in the SM effective field theory (SMEFT)
Summary
We introduce extra leptons which couple to the muons and have vectorlike masses.. Note that the mass matrix M0 does not contribute to neutrino masses, i.e., avoiding too heavy neutrinos These mass matrices are diagonalized as UL0†M0UR0 = diag(mi0 ), UL−−†M−−UR−− = diag(mi−− ). After decoupling the extra leptons, whose masses are typically given by the vectorlike mass Mi, they contribute to low-energy observables through higher dimensional operators in the SMEFT. After the EWSB, the above operators modify the interactions of the Higgs, W and Z bosons from the SM predictions and affect low-energy observables.
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