Speaker
Description
High-energy astrophysical neutrinos offer a unique opportunity to investigate possible interactions between dark matter and Standard Model particles. In particular, neutrinos produced near active galactic nuclei may traverse the enhanced dark matter densities expected around supermassive black holes, where dark matter--neutrino scattering could produce observable attenuation and spectral redistribution in the detected neutrino flux. We develop a likelihood-based statistical framework to search for such signatures using publicly available IceCube point-source data from four candidate neutrino-emitting active galaxies: NGC~1068, NGC~4151, TXS~0506+056, and PKS~1424+240. The expected event distributions are calculated by incorporating dark matter density-spike models, neutrino production spectra, detector effective areas, and propagation effects. Both energy-independent and linearly energy-dependent dark matter--neutrino scattering cross sections are considered. Constraints are obtained using a Poisson likelihood-based $\chi^{2}$ analysis, first for each source independently and subsequently through a joint stacking analysis in which a common dark matter mass and interaction cross section are fitted across all four sources. The combined analysis significantly improves the sensitivity relative to individual-source searches and yields tight upper limits on the dark matter-neutrino scattering cross section for an energy-independent interaction under the most optimistic dark matter spike scenario. The statistical importance of individual sources depends on both their event statistics and their energy distributions. The results are also interpreted within an anomaly-free $U(1)_{L_{\mu}-L_{\tau}}$ model containing pseudo-Dirac or complex-scalar dark matter, demonstrating the potential of statistically combined astrophysical-neutrino observations to constrain otherwise inaccessible dark-sector parameter space.