Energy-dependent flavour ratios in neutrino telescopes from charm

TL;DR

This paper investigates how energy-dependent neutrino flavour ratios from astrophysical sources like supernovae can reveal details about their production mechanisms and flavor mixing, using IceCube data projections.

Contribution

It demonstrates the impact of different spectral shapes and initial flavor compositions on observed neutrino fluxes and explores the potential of IceCube to distinguish these effects.

Findings

Energy-dependent flavor ratios can indicate source characteristics.

Charm production influences neutrino flavor composition at high energies.

Future IceCube measurements could differentiate between source models.

Abstract

The origin of the observed diffuse neutrino flux is not yet known. Studies of the relative flavour content of the neutrino flux detected at Earth can give information on the production mechanisms at the sources and on flavour mixing, complementary to measurements of the spectral index and normalisation. Here we demonstrate the effects of neutrino fluxes with different spectral shapes and different initial flavour compositions dominating at different energies, and we study the sensitivity of future measurements with the IceCube Neutrino Observatory. Where one kind of flux gives way to another, this shows up as a non-trivial energy dependence in the flavour compositions. We explore this in the context of slow-jet supernovae and magnetar-driven supernovae -- two examples of astrophysical sources where charm production may be effective. Using current best-fit neutrino mixing parameters and their projected 2040 uncertainties, we use event ratios of different event morphologies at IceCube to illustrate the possibilities of distinguishing the energy dependence of neutrino flavour ratios.