Asymmetric dark matter from a GeV hidden sector

Asymmetric dark matter (ADM) models relate the dark matter (DM) density to the baryon asymmetry, so that a natural mass scale for ADM is around a few GeV. In existing models of ADM, this mass scale is unexplained; here we generate this GeV scale for DM) from the weak scale via gauge kinetic mixing with a new Abelian dark force. In addition, this dark sector provides an efficient mechanism for suppressing the symmetric abundance of DM through annihilations to the dark photon. We augment this sector with a higher dimensional operator responsible for communicating the baryon asymmetry to the dark sector. Our framework also provides a DM candidate for gauge mediation models. It results in a direct detection cross section of interest for current experiments: ${\sigma }_p\lesssim {10}^{-41}{\mathrm{cm}}^2$ for DM masses in the range 1–15 GeV.

Figure 1

The spectrum of the SUSY model. We have illustrated the mass pattern of the $S/T$ multiplet (not to scale) since this splitting determines the identity of the DM. The splittings within the dark photon multiplet have been suppressed.

Figure 2

Constraints in the $ϵ\mathrm{\text{−}}{g}_d$ plane. We have shown the regions which are excluded by BBN constraints due to ${\tilde{\gamma }}_d\to \gamma \tilde{G}$ [41] (orange), $B$ factories due to direct searches for ${\gamma }_d$ [34] (green), and precision electroweak measurements due to ${\gamma }_d\mathrm{\text{−}}{Z}^0$ mixing [37] (brown). The red region corresponds to parameters which solve the lithium-7 problem [41]. On the left (right) we show contours where $\lambda$ is constrained so as not to reach Landau pole before $M_{\mathrm{GUT}}$ (10 TeV) for $m_{\mathrm{DM}}=14.2\mathrm{GeV}$, $m_{\mathrm{DM}}=7.1\mathrm{GeV}$ and $m_{\mathrm{DM}}=3.3\mathrm{GeV}$, assuming $\sqrt{⟨D_Y⟩}=72\mathrm{GeV}$. The region below these contours is excluded.

Figure 3

The one-loop diagram which generates the $S$ number violating mass $b_S$.

Figure 4

The predictions for the direct detection scattering cross sections normalized per proton (${\sigma }_p$) for $m_{\mathrm{DM}}=14.2\mathrm{GeV}$, 7.1 GeV and 3.3 GeV. We have plotted current/projected limits (also normalized per proton) from Xenon-10 (solid black line), Xenon-100 with 6000 kg-days (dashed green line), Xenon-1T (dotted blue line) [47], and Majorana (dot-dashed purple line) [48].