Inelastic Majorana Dark Matter and Its Self-Interactions in a Gauged $U(1)_{L_μ- L_τ}$ Model (2512.05694v1)

Abstract: We develop an inelastic Majorana dark matter model gauged by $U(1){Lμ-L_τ}$ symmetry, featuring a complex scalar and fermions with a small Dirac mass. The model exhibits strong interactions between the dark fermion-antifermion pair and the scalar, with a large coupling generating a Majorana mass after symmetry breaking. The dark fermion splits into two nearly degenerate Majorana eigenstates, with the $U(1){Lμ-L_τ}$ gauge boson $Z^\prime$ interacting via inelastic axial vector currents. The lighter Majorana serves as dark matter (DM), while the heavier may also contribute. The model predicts DM masses ranging from about 10 GeV to hundreds of GeV, with the scalar favored below 100 MeV. Strong coupling causes DM particles to mainly annihilate into two scalars, which determines the relic abundance, while thermal equilibrium with the bath occurs through $Z^\prime$ interactions. Self-interacting DM particles scatter via ladder exchange of strongly coupled light scalars, helping resolve small-scale issues. The $Z^\prime$ interacts with the muon, affecting its magnetic moment and explaining the $(g-2)μ$ discrepancy. Effects on experiments, $N{\text{eff}}$, and the Hubble tension from kinetic mixing between $Z^\prime$ and the photon, originating from high-energy scales, are discussed. The model details and parameter constraints used in experiments are also covered.