Probing the muon g_\mu-2 anomaly, L_{\mu} - L_{\tau} gauge boson and Dark Matter in dark photon experiments

Abstract

In the L_{\mu} - L_{\tau} model the 3.6$\sigma$ discrepancy between the predicted and measured values of the anomalous magnetic moment of positive muons can be explained by the existence of a new dark boson Z' with a mass in the sub-GeV range, which is coupled at tree level predominantly to the second and third lepton generations. However, at the one-loop level, the Z' coupling to electrons or quarks can be induced via the \gamma -Z' kinetic mixing, which is generated through the loop involving the muon and tau lepton. This loophole has important experimental consequences since it opens up new possibilities, in particular for the complementary searches of the Z' in the ongoing NA64 and incoming dark photon experiments with high-energy electrons. An extension of the model able to explain relic Dark Matter density is also discussed.