The Neutrino Aria of Black Holes: Listening in on Silent Dark Matter ✦

Original: "Neutrino superradiance constraint on asteroid-mass PBH Dark Matter and beyond"

· Yi-Xuan Lin, Priyanka Sarmah, Martin Spinrath

arXiv:2607.12485 · 2026-07-14 · CC BY · 1 min · HEP Phenomenology Cosmology

Rotating primordial black holes could turn into neutrino loudspeakers – their silence places the tightest limits on dark matter.

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A tiny black hole the size of a proton and the mass of an asteroid can become a gravitational amplifier, emitting neutrinos on a single pure note. Physicists scanned the sky with detectors — and the silence spoke louder than hundreds of hypothetical signals, placing unprecedented limits on dark matter. New observatories like JUNO may catch a solo performance from such a hole — and then we will hear the voice of the dark world for the first time.

🎯 If an asteroid-mass PBH of 10^20 g were to enter the Solar System, its size would be comparable to a proton (radius about 0.1 fm), and its spin could spawn a boson cloud radiating millions of neutrinos per second.

\alpha_g \equiv G_N m_\phi M_{\rm PBH}/(\hbar c) \approx 0.75 \left(\frac{m_\phi}{10^{-10}~\text{eV}}\right) \left(\frac{M_{\rm PBH}}{M_\odot}\right)

The gravitational fine-structure constant α_g is a dimensionless parameter that determines the coupling strength between a light scalar field and a black hole. When α_g ~0.3, the cloud efficiently extracts rotational energy.

\bar{E}_\nu^s \approx 2.7\times 10^{10} \left(\frac{g_{\nu\phi}}{10^{-4}}\right) \left(\frac{\Psi_0}{10^{12}~\text{GeV}}\right)~\text{MeV}

The energy of emitted neutrinos is proportional to the coupling constant g_{νϕ} and the amplitude of the scalar field. For weak coupling, neutrinos have energies of a few MeV — right in the detectors' operational range.

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The Neutrino Aria of Black Holes: Listening in on Silent Dark Matter ✦