Resonant neutrino flavor conversion within dark matter spikes

Abstract

We investigate how neutrino--dark matter (DM) interactions modify the flavor composition of high-energy neutrinos from active galactic nuclei (AGNs). Coherent forward scattering in a DM spike around the central supermassive black hole can generate a flavor-dependent potential, inducing flavor conversion as the neutrinos escape. We calculate the flavor composition at Earth for pion-decay and muon-damped sources and find substantial departures from vacuum-oscillation expectations. At neutrino energies around $100\mathrm{TeV}$, the matter potential begins to compete with vacuum oscillations when the coupling-weighted net DM number density reaches $|{\epsilon }_{\alpha }(n_{\chi }-n_{\bar{\chi }})|\sim 10^{18}{\mathrm{cm}}^{-3}$. We compare our predictions with IceCube flavor triangle measurements under the illustrative assumption that the diffuse flux originates from AGNs with common neutrino-production and DM-spike properties. Under this assumption, when the DM-induced potential acts on the muon flavor and dominates the vacuum terms at production, the $p\gamma$ muon-damped predictions lie outside the 95\% MESE contour. High-energy neutrino flavor measurements can therefore provide a novel probe of neutrino-DM interactions in astrophysical environments.

11 pages, 8 figures