Neutrinophilic Super-Resonant Dark Matter

Abstract

Dark matter (DM) annihilation can be significantly enhanced through narrow resonances or the Sommerfeld enhancement effect, with both mechanisms potentially combining in a super-resonant annihilation process. In such scenarios, the conventional assumption that kinetic equilibrium persists until chemical decoupling may not hold, leading to substantial impacts on the final DM relic density. However, a strongly enhanced annihilation cross section into Standard Model particles, except neutrinos, is constrained by cosmic microwave background observations. We thus investigate DM annihilation into neutrino pair final states, focusing on the role of kinetic decoupling. We solve the coupled Boltzmann equations to determine the relic density and constrain the parameter space using current experimental data, while also forecasting the sensitivity of future experiments.

Figures (3)

• Figure 1: Leading Feynman diagram for DM super-resonant annihilation.
• Figure 2: Sommerfeld ($S_{\rm SF}(v)$, dotted lines), resonance ($R(v)$, dashed lines), and SREFs ($S_{\rm SF}(v) \times R(v)$, solid lines) as a function of velocity for different $\rho$, $\alpha$, and $\delta$ values. DM mass is fixed to 1000 GeV. Black and blue lines are for positive and negative $\delta$ values respectively. Black lines are overlapped with blue lines if not appear in the sub-figures.
• Figure 3: Viable and constrained parameter space in the $\rho$ vs. $\alpha_A$ plane for different DM masses. The color bar represents the ratio $\Omega h^2_{cBE} / \Omega h^2_{nBE}$, where $\Omega h^2_{cBE}$ and $\Omega h^2_{nBE}$ are relic densities from the cBEs and nBE, respectively. Dashed blue and green lines indicate $\Omega h^2_{cBE} = 0.118$ and $\Omega h^2_{nBE} = 0.118$, respectively. Solid red lines represent current upper limits for DM annihilation cross section from neutrino experiment ANTARES Gozzini:2020dom and "Unitarity Bound" for non-composite DM particle Griest:1989wdSmirnov:2019ngs, while dotted red lines show future prospects from KM3Net Gozzini:2020dom. Thick black lines denote BBN constraints. Solid and dotted yellow line represent current limit and future sensitivities to the $y_\nu$ and $\Delta N_{\rm eff}$. Solid purple line represent limits from CMB. Currently excluded regions, right sides of solid purple/red lines and left sides of solid yellow lines, are shaded with gray. Annihilation cross section limits are: $\langle \sigma v \rangle_{\rm ANTARES} = 1.7 \times 10^{-24}$ cm$^3$ s$^{-1}$ for $m_\chi = 100$ GeV; $\langle \sigma v \rangle_{\rm ANTARES} = 1.1 \times 10^{-24}$ cm$^3$ s$^{-1}$, $\langle \sigma v \rangle_{\rm CMB} = 6.4 \times 10^{-20}$ cm$^3$ s$^{-1}$, and $\langle \sigma v \rangle_{\rm KM3Net} = 8.8 \times 10^{-26}$ cm$^3$ s$^{-1}$ for $m_\chi = 1000$ GeV; $\langle \sigma v \rangle_{\rm ANTARES} = 2.0 \times 10^{-24}$ cm$^3$ s$^{-1}$, $\langle \sigma v \rangle_{\rm CMB} = 1.2 \times 10^{-20}$ cm$^3$ s$^{-1}$, and $\langle \sigma v \rangle_{\rm KM3Net} = 1.4 \times 10^{-25}$ cm$^3$ s$^{-1}$ for $m_\chi = 10$ TeV; $\langle \sigma v \rangle_{\rm Unitarity\ bound} = 8.0 \times 10^{-24}$ cm$^3$ s$^{-1}$, $\langle \sigma v \rangle_{\rm CMB} = 6.4 \times 10^{-22}$ cm$^3$ s$^{-1}$, and $\langle \sigma v \rangle_{\rm KM3Net} = 1.4 \times 10^{-24}$ cm$^3$ s$^{-1}$ for $m_\chi = 100$ TeV.