Muon g-2 Anomaly and Dark Leptonic Gauge Boson

Abstract

One of the major motivations to search for a dark gauge boson of MeV-GeV scale is the long-standing muon g-2 anomaly. Because of active searches such as fixed target experiments and rare meson decays, the muon g-2 favored parameter region has been rapidly reduced. With the most recent data, it is practically excluded now in the popular dark photon model. We overview the issue and investigate a potentially alternative model based on the gauged lepton number or U(1)_L. The muon g-2 favored parameter region of the U(1)_L survives all the constraints that were critical in the dark photon case, yet it is disfavored by the new constraints from the large flux neutrino experiments.