Leptonic anomalous magnetic moments in $\nu$SMEFT

TL;DR

This paper explores how $ u$SMEFT operators can explain the observed discrepancies in the anomalous magnetic moments of leptons, identifying specific operators and experimental avenues for testing these explanations.

Contribution

It demonstrates that a particular right-handed charged current operator within $ u$SMEFT can account for lepton magnetic moment anomalies with sterile neutrino masses around 100 GeV, consistent with existing constraints.

Findings

A single $ u$SMEFT operator can explain electron and muon magnetic moment discrepancies.

Sterile neutrino masses of about 100 GeV are compatible with the proposed explanation.

Multiple experimental searches can further test the proposed new physics scenario.

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 $h\rightarrow \mu^+ \mu^-$ and searches for $h\rightarrow e^+ e^-$, neutrinoless double beta decay experiments, and improved unitarity tests of the CKM matrix can further probe the relevant parameter space.