Anomalies in 8Be nuclear transitions and (g − 2)e,μ: towards a minimal combined explanation
C. Hati, J. Kriewald, J. Orloff, A.M. Teixeira
Abstract
A bstract Motivated by a simultaneous explanation of the apparent discrepancies in the light charged lepton anomalous magnetic dipole moments, and the anomalous internal pair creation in 8 Be nuclear transitions, we explore a simple New Physics model, based on an extension of the Standard Model gauge group by a U(1) B−L . The model further includes heavy vector-like fermion fields, as well as an extra scalar responsible for the low-scale breaking of U(1) B−L , which gives rise to a light Z′ boson. The new fields and currents allow to explain the anomalous internal pair creation in 8 Be while being consistent with various experimental constraints. Interestingly, we find that the contributions of the Z′ and the new U(1) B−L -breaking scalar can also successfully account for both ( g − 2) e,μ anomalies; the strong phenomenological constraints on the model’s parameter space ultimately render the combined explanation of ( g − 2) e and the anomalous internal pair creation in 8 Be particularly predictive. The underlying idea of this minimal “prototype model” can be readily incorporated into other protophobic U(1) extensions of the Standard Model.