Threshold effects of inelastic neutrino-dark-matter scattering in AGN spikes
Abstract
High-energy neutrinos from active galactic nuclei provide a powerful probe of dark matter (DM) spikes surrounding supermassive black holes. While elastic neutrino-DM scattering mediated by a light particle produces little net attenuation due to regeneration, inelastic scattering, νχ1→νχ2, introduces a nonzero minimum energy loss, Eth. We show that this threshold prevents the near-cancellation between attenuation and regeneration, producing a distinctive spectral deficit above Eth accompanied by a pile-up below it. Solving the full neutrino cascade, including repeated scattering and secondary neutrinos from excited-state decays, we demonstrate that this feature persists for both narrow and broad energy-transfer kernels. Using public IceCube data for NGC 1068 and an unbinned likelihood analysis with a freely fitted intrinsic power-law spectrum, we derive upper limits on the asymptotic optical depth of τ0<26−39 for a narrow kernel (kernel width ε=0.01) over Eth=0.24−3.0 TeV and τ0<20−26 for a broad kernel (ε=0.36) over Eth=0.24−2.4 TeV, at the nominal 90% confidence level. An intrinsic high-energy cutoff weakens the narrow-kernel limits by factors of 2.2−7.4 and the broad-kernel limits by factors of 2.0−5.0. We further investigate DM velocity effects and combine NGC 1068 with CGCG 420-015 and TXS 0506+056 to extend the threshold reach. In a vector-mediator realization, an optimistic adiabatic DM spike can yield constraints on the neutrino coupling competitive with laboratory bounds for broad energy-transfer kernels.
Related
- Solar Neutrino Constraints on Inelastic Dark Matter Scattering in Light of Recent LUX-ZEPLIN Observations
- Revisiting bounds on neutrino dark matter interaction at spikes
- Resonant neutrino flavor conversion within dark matter spikes
- The neutrino fog for inelastic dark matter
- Inelastic Scattering Effects on Attenuation of Boosted Dark Matter
BibTeX
@misc{chiang2026threshold,
title = {{Threshold effects of inelastic neutrino-dark-matter scattering in AGN spikes}},
author = {Cheng-Wei Chiang and Van Que Tran},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.35620},
eprint = {2610.35620},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.35620},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Threshold effects of inelastic neutrino-dark-matter scattering in AGN spikes
AU - Cheng-Wei Chiang
AU - Van Que Tran
PY - 2026
DA - 2026/10/26
PB - arXiv
DO - 10.48550/arxiv.2610.35620
UR - https://arxiv.org/abs/2610.35620
AB - High-energy neutrinos from active galactic nuclei provide a powerful probe of dark matter (DM) spikes surrounding supermassive black holes. While elastic neutrino-DM scattering mediated by a light particle produces little net attenuation due to regeneration, inelastic scattering, νχ_1→νχ_2, introduces a nonzero minimum energy loss, E_th. We show that this threshold prevents the near-cancellation between attenuation and regeneration, producing a distinctive spectral deficit above E_th accompanied by a pile-up below it. Solving the full neutrino cascade, including repeated scattering and secondary neutrinos from excited-state decays, we demonstrate that this feature persists for both narrow and broad energy-transfer kernels. Using public IceCube data for NGC 1068 and an unbinned likelihood analysis with a freely fitted intrinsic power-law spectrum, we derive upper limits on the asymptotic optical depth of τ_0<26−39 for a narrow kernel (kernel width ε=0.01) over E_th=0.24−3.0 TeV and τ_0<20−26 for a broad kernel (ε=0.36) over E_th=0.24−2.4 TeV, at the nominal 90% confidence level. An intrinsic high-energy cutoff weakens the narrow-kernel limits by factors of 2.2−7.4 and the broad-kernel limits by factors of 2.0−5.0. We further investigate DM velocity effects and combine NGC 1068 with CGCG 420-015 and TXS 0506+056 to extend the threshold reach. In a vector-mediator realization, an optimistic adiabatic DM spike can yield constraints on the neutrino coupling competitive with laboratory bounds for broad energy-transfer kernels.
ER -