PHYSICAL REVIEW D
One of the major motivations to search for a dark gauge boson of MeV-GeV scale is the long-standing g(mu) - 2 anomaly. Because of active searches such as fixed target experiments and rare meson decays, the g(mu) - 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 g(mu) - 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.
Lee, Hye-Sung; Lee, Hye-Sung; and Lee, Hye-Sung, Muon g-2 anomaly and dark leptonic gauge boson (2014).