The Low-Scale Seesaw Solution to the $M_W$ and $(g-2)_\mu$ Anomalies

Abstract

The recent CDF-II measurement of the $W$-boson mass shows a strong tension with the corresponding Standard Model prediction. Once active neutrino masses are explained in the context of the Low-Scale Seesaw mechanisms, this tension can be resolved. We investigate the possibility of explaining the longstanding muon anomalous magnetic moment anomaly within the same frameworks. We present a simplified extension of the Standard Model, accounting only for the second lepton generation, that describes a massive active neutrino and provides a combined solution to these anomalies. The model is renormalisable and introduces in the spectrum, beyond the sterile species of the Low-Scale Seesaw mechanism, only one pair of exotic vector-like leptons, doublets under the electroweak symmetry. We moreover discuss the extension of this model to the realistic three-family case.