LIght scalars with lepton number to solve the $(g-2{)}_e$ anomaly

Scalars that carry lepton number can help mediate would-be lepton-number-violating processes, such as neutrinoless double $\beta$ decay or lepton-scattering-mediated nucleon-antinucleon conversion. Here we show that such new scalars can also solve the anomaly in precision determinations of the fine-structure constant $\alpha$ from atom interferometry and from the electron’s anomalous magnetic moment, $a_e\equiv (g-2{)}_e\mathrm{/}2$, by reducing $\mathrm{\mid }{a}_e\mathrm{\mid }$. Study of the phenomenological constraints on these solutions favor a doubly-charged scalar with mass below the GeV scale. Significant constraints arise from the measurement of the parity-violating asymmetry in M{\o}ller scattering, and we consider the implications of the next-generation MOLLER experiment at Jefferson Laboratory and of an improved $a_e$ measurement.