Boosted dark matter versus dark matter-induced neutrinos from single and stacked blazars

TL;DR

This work links sub-GeV dark matter around blazars to two observable channels: neutrinos produced by DM–proton inelastic scatterings in jets and a boosted DM flux reaching Earth that can be detected via proton recoils in large detectors. By implementing energy-dependent elastic and inelastic cross sections for scalar, pseudoscalar, vector, and axial mediators, the authors compute BBDM fluxes for TXS 0506+056 and a 324-blazar sample, incorporating Earth attenuation and detector responses to derive current bounds and future sensitivities at SK, HK, JUNO, and DUNE. They compare these BBDM constraints with neutrino predictions and withmodel-dependent and model-independent limits, showing that sub-GeV DM explanations of IceCube events can remain viable in several scenarios, while in others they are challenged by BBDM searches. Spike depletion by jets is analyzed and found to be non-negligible for some spike benchmarks but not for the blazar sample, reinforcing the robustness of the diffuse BBDM signal and its complementarity to neutrino observables. The study emphasizes the importance of explicit mediator models and astrophysical DM profiles when testing blazar-DM scenarios and outlines paths for future refined analyses and time-dependent source modeling.

Abstract

The physics responsible for the production of observed high-energy neutrinos have not been established so far, neither for the diffuse astrophysical ones nor for those detected from single blazars. We recently proposed that both could be explained by deep inelastic scatterings between sub-GeV dark matter (DM) around blazars and protons within their jets. Here, we compute the proton-recoil signals at the neutrino detectors Super-Kamiokande, KamLAND, Borexino, JUNO, Hyper-Kamiokande and DUNE induced by DM that is itself boosted by the scatterings with protons in blazar jets. We do it for the four cases of vector, axial, scalar and pseudoscalar mediators of DM-quark interactions. We perform the analysis for the single blazar TXS 0506+056 and for a sample of more than 300 stacked blazars. We find that searches for such blazar-boosted DM leave room for a variety of DM models to explain observations of high-energy neutrinos. We check that the depletion of the DM spike induced by DM-proton and DM-DM interactions does not compromise the DM interpretation for high-energy neutrinos, but challenges other blazar-DM signals.

Figures (13)

• Figure 1: The DM density profile $\rho_\mathsmaller{\mathrm{DM}}(r)$ (solid green, left axis) and its column density $\Sigma_{\mathsmaller{\mathrm{DM}}}(r)$ (solid purple, right axis) for BH mass $M_{\mathsmaller{\mathrm{BH}}}=3 \times 10^8 M_\odot$. The DM column density is plotted for the two BMCs: $R_{\mathsmaller{\mathrm{min}}} = 10^2 R_S$ (BMCI, upper curve) and $R_{\mathsmaller{\mathrm{min}}} = 10^4 R_S$ (BMCII, lower curve). We also plot the DM profile $\tilde{\rho}_\mathsmaller{\mathrm{DM}}(r)$ (green dashed) which includes DM annihilations for the maximal values of $\left\langle \sigma_\text{ann} v_\text{rel}\right\rangle$ which yield $\Sigma_{\mathsmaller{\mathrm{DM}}}$ consistent with BMCI and BMCII, taking the BH lifetime $t_{\mathsmaller{\mathrm{BH}}}=10^{10}$ yr and DM mass $m_\chi=1$ GeV.
• Figure 2: Time delay of the BBDM flux at Earth with respect to the photons emitted by TXS 0506+056 (black solid) and the blazar sample (gray area) as a function of $T_\chi/m_\chi$. Also shown in dashed is the cut $T_\chi/m_\chi\geq 0.104$ (vertical line) and the relative $\Delta t=t_\mathsmaller{\mathrm{DM}}-t_\text{light}$ (horizontal line) for TXS 0506+056 obtained by imposing $t_\mathsmaller{\mathrm{DM}} \leq t_\mathsmaller{\mathrm{BH}}\simeq 10^{10}$ yr. In the darker gray region we find $t_\mathsmaller{\mathrm{DM}}(z) \geq t_{\rm Universe} \simeq 1.379\times 10^{10}\,\text{yr}$ for the considered sample of blazars.
• Figure 3: BBDM flux at Earth surface from TXS 0506+056 for $m_\chi = 1\,\text{MeV}$ (blue), $10\,\text{MeV}$ (orange), $100\,\text{ MeV}$ (green), $1\,\text{GeV}$ (red). Dashed (solid) curves correspond to the elastic (elastic + DIS) contribution, for a scalar (first row), pseudoscalar (second row), vector (third row) and axial (last row) mediator with mass $m_Y=500\,\text{MeV}$ (left panels) and $5\,\text{GeV}$ (right panels). The plots are obtained for $g_{\chi Y} g_{u Y} = g_{\chi Y} g_{dY} = 0.1$ and $\Sigma_\mathsmaller{\mathrm{DM}} = 6.9\times10^{28}\,\text{GeV}\,\text{cm}^{-2}$. The thick (thin) lines are obtained after imposing the cut $T_\chi/m_\chi\geq 0.104$ ($< 0.104$). Note: the range of the vertical axes differ between left and right panels.
• Figure 4: BBDM flux from 324 blazars for scalar (top), pseudoscalar (second row), vector (third row), and axial (bottom) mediators. Gray lines show individual blazars; red highlights 3C 371, which dominates the flux; black is the total excluding 3C 371. Dashed and solid lines represent elastic and elastic + DIS contributions, respectively. We fix $m_Y=500\,\text{MeV}$ ($m_Y = 5\,\text{GeV}$) in the left (right) panels, with $m_\chi = 10\,\text{MeV}$, and the overall normalisation with $g_{\chi Y} g_{u Y} = g_{\chi Y} g_{dY} = 0.1$ and $\Sigma^{\rm spike}_\mathsmaller{\mathrm{DM}}$ as in BMCI. For each blazar we have imposed the cut on $T_\chi/m_\chi$ that results from the condition $t_{\mathsmaller{\mathrm{DM}}} \leq t_{\rm Universe} \simeq 1.379\times 10^{10}\,\text{yr}$. Note: the range of the vertical axes differ between left and right panels.
• Figure 5: Distance $x$ travelled by DM in the Earth crust, in units of the mean path $\ell$ travelled by DM before it undergoes a scattering with nucleons, as a function of the DM kinetic energy at surface $T_\chi^{\mathsmaller{\mathrm{(0)}}}$. We consider the cases of scalar, pseudoscalar, vector and axial mediators and we choose as benchmark values $x=1\,\text{km}$, $m_Y=500\,\text{MeV}$ ($5\,\text{GeV}$), $m_\chi=10\,\text{MeV}$, 100 MeV$, 1\,\text{GeV}$ and $g_{\chi Y} g_{q Y} = 0.1$ for the left (right) panel. Attenuation effects become relevant when $N_{\rm sct}\geq 1$ (thick black line). Inside the gray shaded areas, one for each value of DM mass, we have $Q^2<0.04\,\text{GeV}^2$ and the DM scattering with nuclei, which we have not included in our treatment, is dominant. We stress that the differences among the various mediator cases, at large $T_\chi^{(0)}$ arise as an artifact of our conservative approximation of considering the elastic scattering cross sections with form factors evaluated at zero momentum transfer.