Neutrino Portal Dark Matter: From Dwarf Galaxies to IceCube

TL;DR

The paper proposes a neutrinophilic dark matter model (SνDM) where DM X and a secluded SM-singlet neutrino νs interact via a light MeV-scale mediator φ and a new U(1)X gauge symmetry, with active–νs mixing enabling communication between the dark and visible sectors. The framework yields late kinetic decoupling, sizable DM self-interactions at dwarf scales, and a relic population of secluded neutrinos, potentially addressing cusp-versus-core, missing satellites, and too-big-to-fail problems. Crucially, active–secluded neutrino mixing plus νs self-interactions modify the mean free path of ultra-high-energy neutrinos, producing observable absorption features or source correlations in IceCube and constraining the model’s parameter space. The study demonstrates that a broad region of parameter space can simultaneously resolve small-scale structure issues and yield testable IceCube signatures, offering a unique avenue to probe the dark sector through high-energy neutrinos and cosmology.

Abstract

It has been suggested that the baseline scenario of collisionless cold dark matter over-predicts the numbers of satellite galaxies, as well as the dark matter (DM) densities in galactic centers. This apparent lack of structure at small scales can be accounted for if one postulates neutrino-DM and DM-DM interactions mediated by light O(MeV) force carriers. In this letter, we consider a simple, consistent model of neutrinophilic DM with these features where DM and a "secluded" SM-singlet neutrino species are charged under a new $U(1)$ gauge symmetry. An important ingredient of this model is that the secluded sector couples to the Standard Model fields only through neutrino mixing. We observe that the secluded and active neutrinos recouple, leading to a large relic secluded neutrino population. This relic population can prevent small-scale halos from collapsing, while at same time significantly modifying the optical depth of ultra-high-energy neutrinos recently observed at Icecube. We find that the bulk of the parameter space accommodating an (a)symmetric thermal relic has potentially observable consequences for the IceCube high energy signal, with some of the parameter ranges already ruled out by the existing data. Future data may confirm this mechanism if either spectral absorption features or correlations with nearby sources are observed.

Figures (4)

• Figure 1: The relevant Feynman diagrams for (1) the relic abundance, (2) DM-DM self-scattering, and (3) $\nu$-DM scattering relevant for addressing the missing satellites problem.
• Figure 2: In the left and right panels we fix the mediator mass to 10 MeV and 1 MeV respectively. To address the cusp-versus-cores and too-big-to-fail problems a parameter point should lie within the shaded blue region. Values to the left of the black curve lead are excluded by producing an over-abundance of DM, $\Omega_{DM} h^{2} > 0.12$. Regions to the right of the green curve are excluded by Lyman-$\alpha$ requirements that $M_{halo} < 5 \times 10^{10}~M_{\odot}$, while regions to the right of the red solid line are excluded by having a MFP $<$ 50 Mpc. In the region to the right of the dashed red IceCube can perform source correlations at 3$\sigma$ (see text for details). For reference the dashed green curves are contours of constant $M_{halo} = 10^{5}~M_{\odot},10^{7}~M_{\odot}, 10^{9}~M_{\odot}$ from left to right. Arrows indicate the direction in which the parameter space is allowed.
• Figure 3: Here we illustrate the effect of neutrino scattering on the fraction of events at IceCube originating within a given redshift, $z$. Notice that when absorption is present, a larger fraction of events originate from nearby, and may be more easily correlated with known sources.
• Figure 4: Left: 2D projection along the $m_\phi$ axis showing the regions of the $m_X$-$g_X$ parameter space which may potentially solve the dark matter structure problems while producing identifiable absorption features for the IceCube experiment. Right: 2D projection along the $m_X$ axis showing the regions of the $m_\phi$-$g_X$ parameter space which may potentially solve the dark matter structure problems while producing identifiable absorption features for the IceCube experiment. Blue indicates the regime where the C$\nu$B is opaque to high energy neutrinos on distances less than $50\,\rm Mpc$, orange color indicates regimes where the C$\nu$B is opaque to high energy neutrinos on distances short enough that absorption might be detected via IceCube source correlations at the level of $3\sigma$ statistical significance (using the 3 year data set Aartsen:2014uq), purple indicates the regime where there absorption of high energy neutrinos may alter the IceCube observed spectra without creating a significant source correlation, red indicates the regime where the absorption of high energy neutrinos reconciles the over abundance of IceCube events correlated with BL Lacs at $z < 0.212$, and dark grey regions show the regime where the C$\nu$B is optically thin out to $z=10$.