Neutrino-Devouring Process in Supernovae

• The neutrino-devouring process is defined as the conversion of supernova neutrinos into dark sector fermions via scattering with electrons or nucleons, mediated by effective higher-dimensional operators.
• This mechanism introduces an extra cooling channel for proto-neutron stars, potentially altering neutrino burst durations and conflicting with SN1987A observations by exceeding standard energy loss limits.
• Simulations impose tight limits on dark matter coupling strengths, with electron and nucleon cross sections constrained to 10⁻⁵¹–10⁻⁵⁸ cm² and 10⁻⁴⁹–10⁻⁵⁶ cm² respectively in the keV–MeV mass range.

The neutrino-devouring process refers to interaction channels in astrophysical environments, specifically core-collapse supernovae, where copiously produced supernova neutrinos are converted into dark sector particles. This conversion results in an additional, potentially dominant, cooling channel for the proto-neutron star, with observable consequences for supernova neutrino signals. In recent work, this term describes the production of fermionic dark matter (DM) via neutrino scattering with electrons or nucleons in the supernova core, mediated by effective higher-dimensional operators (Lin et al., 29 Jul 2025). Tight upper limits on DM coupling strength are placed by the requirement that this non-standard energy loss does not exceed observed supernova cooling rates.

1. The Neutrino-Devouring Mechanism

The primary process involves high-density, thermal supernova neutrinos (T ~ 30 MeV) undergoing scattering with ambient electrons or nucleons, producing a dark matter fermion (χ) via reactions of the schematic form: $$\nu + e \to \chi + e \qquad \text{and analogously} \qquad \nu + N \to \chi + N$$ where $N$ denotes a nucleon (proton or neutron). The process is realized via effective dimension-six operators parameterizing new physics:

• Vector-type: $$O_V = \frac{1}{\Lambda^2}(\bar{\chi}\gamma^\mu P_L \nu)(\bar{e} \gamma_\mu e)$$
• Scalar-type: $$O_S = \frac{1}{\Lambda^2}(\bar{\chi} P_L \nu)(\bar{e} e)$$

$\Lambda$ is the scale of new physics (mass of the heavy mediator), and $\nu$ are SM left-handed neutrinos.

The cross sections for these operators (in the center-of-mass frame), accounting for supernova core conditions, are given by: $$\sigma^V_{\nu e} = \left( \frac{x}{12\pi \sqrt{s} \Lambda^4} \right) [3\tilde{E}_\chi (2\tilde{E}_e \tilde{E}_e' + \tilde{E}_\nu \tilde{E}_e' - m_e^2) + \tilde{p}_f^2 (3\tilde{E}_e + 4\tilde{E}_\nu)]$$

$x = \frac{\tilde{p}_f}{\tilde{E}_e}$

and similar forms for the scalar interaction (Lin et al., 29 Jul 2025).

The dark matter particle thus produced escapes the supernova, carrying away energy that would otherwise remain in the thermal neutrino bath, effectively enhancing the core's cooling rate.

2. Consequences for Supernova Cooling

Ordinarily, the vast majority of supernova gravitational binding energy is radiated as neutrinos. The introduction of an additional, significant energy loss channel from DM production increases the proto-neutron star cooling rate. The effect is benchmarked using the Raffelt energy loss criterion, which demands that any non-standard energy loss mechanism does not carry away more than about 10% of the total neutrino luminosity, to be consistent with neutrino signal durations and energies observed from events such as SN1987A.

The total energy loss to DM, integrated over the supernova volume and time-evolving thermodynamic structure, is quantified as: $$E_\chi = \int E_\chi \frac{dN_\chi}{dE_\chi} dE_\chi$$ where the DM energy spectrum is given by: $$\frac{dN_\chi}{dE_\chi}(t, r) \propto \sigma_{\nu e} n_e \frac{dn_\nu}{dE_\nu}$$ with $n_e$ the local electron density, $\sigma_{\nu e}$ the relevant cross section, and $dn_\nu/dE_\nu$ the neutrino energy spectrum at the supernova radius $r$ and time $t$.

If too much energy is carried away in this channel, the expected supernova neutrino burst would be shortened or significantly altered, directly conflicting with observed data—thus allowing stringent tests of DM–neutrino interactions.

3. Constraints on Dark Matter Interactions

By simulating the time-dependent evolution of the post-bounce supernova core (temperature, density, and composition profiles) with state-of-the-art hydrodynamic modeling, the energy loss associated with various DM production cross sections is computed. The resulting upper limits exclude:

• DM–electron cross sections: $\sigma_{\chi e} \lesssim 10^{-51}$–$10^{-58}\,\mathrm{cm}^2$ in the keV–MeV mass range
• DM–nucleon cross sections: $\sigma_{\chi N} \lesssim 10^{-49}$–$10^{-56}\,\mathrm{cm}^2$ in the 0.1–100 MeV mass range

These bounds are several orders of magnitude more stringent than direct detection limits in the corresponding mass range, probing extremely feeble interaction strengths unattainable in laboratory experiments (Lin et al., 29 Jul 2025).

The exclusion is largely robust with respect to the Lorentz structure of the dimension-six operator (vector or scalar), as the dominant energy loss is set by the overall cross section and the high neutrino and electron (or nucleon) densities in the supernova core. Only minor differences arise from variations in the differential cross section.

4. Complementary Constraints and Parameter Space Coverage

Supernova cooling bounds substantially overlap and strengthen global constraints on new light fermionic DM:

• Cosmological: Overproduction via freeze-in or constraints from dark matter decay affect the allowed region, but supernova limits probe smaller couplings.
• Astrophysical: Indirect detection via γ-ray or X-ray telescopes, as well as supernova neutrino observations, provide independent checks.
• Collider (LHC): Mono-jet and missing energy searches constrain DM–nucleon couplings at high cross section, but not at the extremely low couplings addressed here.
• Direct Detection: Experiments such as PandaX-4T, XENONnT, and others set limits at higher masses and coupling strengths, but are superseded at sub-MeV masses by supernova bounds.

The combined constraints, especially for DM coupling to electrons in the keV–MeV mass range, close almost the entire viable parameter space in which such DM comprises an $\mathcal{O}(1)$ fraction of cosmological dark matter (Lin et al., 29 Jul 2025).

Constraint Source	Mass Range	Cross Section Sensitivity (cm²)
Supernova Cooling	keV–100 MeV	$10^{-51}$–$10^{-58}$ (e), $10^{-49}$–$10^{-56}$ (N)
Direct Detection	> MeV	$10^{-46}$–$10^{-42}$
Colliders, Cosmology	Model-dependent	Varies

5. Implications for Particle Physics and Astrophysics

The absence of anomalous supernova cooling consistent with the standard neutrino signal requires that any new weakly coupled fermionic dark matter interacting with electrons or nucleons must have extremely suppressed interaction strengths. This severely restricts models of light (keV–MeV) dark matter satisfying these couplings from constituting the entirety of the observed dark matter abundance through freeze-in or thermal relic scenarios.

Astrophysical environments, such as supernovae, thus provide unique sensitivity to new physics at energy scales inaccessible to terrestrial experiments, especially for models with ultra-weak couplings and sub-GeV masses. This leads to compelling motivation for further exploration of dark sector models, refined simulations of supernova dynamics, and ongoing searches for anomalous cooling or spectral features in neutrino events as indirect probes of new feebly interacting particles.

6. Outlook and Future Directions

The neutrino-devouring scenario continues to serve as a stringent test for physics beyond the Standard Model, with exclusion regions in the parameter space likely to be expanded further as supernova simulations become even more realistic and future neutrino detectors improve their sensitivity to time and spectral features of supernova bursts. Continued theoretical development of DM production mechanisms (including beyond dimension-six interactions and non-minimal mediator sectors), as well as systematic modeling of out-of-equilibrium and multidimensional effects in the supernova core, will provide sharper probes of dark sector physics in extreme astrophysical laboratories.

These results collectively highlight the intersection between astrophysical observations, supernova modeling, neutrino physics, and dark matter theory, underscoring the crucial role of supernovae as cosmic laboratories for beyond-Standard-Model phenomena.