Testing new physics with the electron g-2

TL;DR

The paper discusses how precise measurements of the electron's anomalous magnetic moment can serve as sensitive probes for new physics beyond the Standard Model, especially in light of muon g-2 discrepancies.

Contribution

It highlights the potential of electron g-2 measurements to detect new physics and explores models where electron and muon anomalies are correlated or decoupled.

Findings

Current bounds on new physics contributions to a_e are 8×10^-13.

Future experiments could improve sensitivity by an order of magnitude.

Models exist where a_e effects are larger and correlated with other lepton processes.

Abstract

We argue that the anomalous magnetic moment of the electron (a_e) can be used to probe new physics. We show that the present bound on new-physics contributions to a_e is 8*10^-13, but the sensitivity can be improved by about an order of magnitude with new measurements of a_e and more refined determinations of alpha in atomic-physics experiments. Tests on new-physics effects in a_e can play a crucial role in the interpretation of the observed discrepancy in the anomalous magnetic moment of the muon (a_mu). In a large class of models, new contributions to magnetic moments scale with the square of lepton masses and thus the anomaly in a_mu suggests a new-physics effect in a_e of (0.7 +- 0.2)*10^-13. We also present examples of new-physics theories in which this scaling is violated and larger effects in a_e are expected. In such models the value of a_e is correlated with specific predictions for processes with violation of lepton number or lepton universality, and with the electric dipole moment of the electron.