Widen the resonance at ultra-high energies: novel probes of neutrino self-interactions in the high-mass regime
Abstract
Neutrino self-interaction beyond the Standard Model is well motivated by the nonzero masses of neutrinos, which are the only known particles guaranteed to have new physics. Cosmic messengers, especially neutrinos, play a central role in probing new physics, as they provide experimental conditions far beyond the reach of laboratories and serve as the link between laboratory fundamental-physics discoveries and their roles in the Universe, where many new physics motivations originate. In this work, we propose a novel probe of neutrino self-interactions through ultra-high-energy neutrinos scattering off the cosmic neutrino background when the lightest neutrino species remains relativistic today. This allows us to “Widen the Resonance” of such scattering. Meanwhile, we also provide a semi-analytic framework for cosmogenic UHE neutrino production, avoiding computationally intensive simulations and yielding results precise enough for BSM studies. The widened resonance enables future ultrahigh-energy neutrino telescopes, in particular GRAND, to probe mediator masses from MeV to GeV, reaching couplings down to $g \sim 10^{-3}$ – up to two orders of magnitude beyond current bounds. Our results enhance the discovery potential of $\nu$SI in the high-mass regime, potentially offering crucial insights into the connections between the neutrino sector and dark sector.
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Citation (BibTeX)
@article{Machado:2025ltu,
author = {Machado, Pedro A. N. and Wang, Isaac R. and Xu, Xun-Jie and Zhou, Bei},
title = {{Widen the resonance at ultra-high energies: novel probes of neutrino self-interactions in the high-mass regime}},
eprint = {2512.00165},
archiveprefix = {arXiv},
primaryclass = {hep-ph},
reportnumber = {FERMILAB-PUB-25-0853-T},
doi = {10.1088/1475-7516/2026/07/064},
journal = {JCAP},
volume = {07},
pages = {064},
year = {2026},
}