Flavor of cosmic neutrinos preserved by ultralight dark matter

Within the standard propagation scenario, the flavor ratios of high-energy cosmic neutrinos at neutrino telescopes are expected to be around the democratic benchmark resulting from hadronic sources, ${(1/3:1/3:1/3)}_{\oplus }$. We show how the coupling of neutrinos to an ultralight dark matter complex scalar field would induce an effective neutrino mass that could lead to adiabatic neutrino propagation. This would result in the preservation at the detector of the production flavor composition of neutrinos at sources. This effect could lead to flavor ratios at detectors well outside the range predicted by the standard scenario of averaged oscillations. We also present an electroweak-invariant model that would lead to the required effective interaction between neutrinos and dark matter.

Figure 1

Ternary plot of the flavor composition of cosmic neutrinos. The allowed flavor compositions are represented by the regions within the black lines, using IceCube HESE events after 7.5 years (68% and 95% confidence level), with three types of topologies: muon tracks, single, and double cascades [82]. Also shown is the obtained best fit (black cross). The gray shaded contour indicates the allowed region after standard averaged oscillations during propagation, and accounts for uncertainties at 95% confidence level of the neutrino mixing angles [79]. For hadronic sources, the expected flavor ratio at detection after standard propagation lies at the center (star), whereas within the scenario discussed in this paper, it would coincide with the flavor composition at the source (thick purple dot).