Light vector dark matter with scalar mediator and muon g-2 anomaly

Abstract: We study a model with a vector dark matter (DM) candidate interacting with the SM charged leptons through a scalar portal. The dark matter candidate acquires mass when the complex scalar breaks an abelian gauge symmetry spontaneously. The scalar interacts with the SM charged leptons through a dimension-6 operator. The scalar mediator induces elastic scattering of dark matter with electrons at tree level and also DM-nucleon interaction when the effects from scalar-Higgs mixing are also taken into account. Given the recent results from Xenon1T upper bounds on DM-electron elastic scattering cross section where the strongest sensitivity lies in the range $\sim {\cal O}$(1) GeV, we find the viable space in the parameter space respecting constraints from the observed relic density, direct detection, muon $(g_\mu-2)$ anomaly, $e^+ e^-$ colliders, electron beam-dump experiments and astrophysical observables. It is shown that the current upper bounds of Xenon1T on DM-electron interaction is partially sensitive to the regions in the viable parameter space which is already excluded by the electron beam-dump experiment, Orsay. We also find that there are viable DM particles with masses $\sim {\cal O}(1)$ GeV evading the direct detection but stand well above the neutrino floor. Almost the same viable regions are found when we apply the direct detection upper limits on the DM-proton spin-independent cross section.