Leptonic anomalous magnetic moments in $\nu$SMEFT

Abstract

We investigate contributions to the anomalous magnetic moments of charged leptons in the neutrino-extended Standard Model Effective Field Theory ($\nu$SMEFT). We discuss how $\nu$SMEFT operators can contribute to a lepton's magnetic moment at one- and two-loop order. We show that only one operator can account for existing electronic and muonic discrepancies, assuming new physics appears above $1$ TeV. In particular, we find that a right-handed charged current in combination with minimal sterile-active mixing can explain the discrepancy for sterile neutrino masses of $\mathcal{O}(100)$ GeV while avoiding direct and indirect constraints. We discuss how searches for sterile neutrino production at the (HL-)LHC, measurements of $h\to {\mu }^{+}{\mu }^{-}$ and searches for $h\to e^{+}{e}^{-}$, neutrinoless double beta decay experiments, and improved unitarity tests of the CKM matrix can further probe the relevant parameter space.

Comments: Journal version. 37 pages (incl. references), 6 figures, 4 tables. vSMEFT FeynRules UFO available from https://feynrules.irmp.ucl.ac.be/wiki/HeavyN