Resonant Neutrino Flavor Conversion in the Atmosphere

TL;DR

This paper enhances neutrino flavor evolution modeling by incorporating atmospheric density variations, revealing a new resonance that significantly impacts muon neutrino fluxes observed by IceCube.

Contribution

It extends the {nuSQuIDS} code to include atmospheric density effects, demonstrating a new resonance phenomenon affecting neutrino oscillations at high energies.

Findings

Resonance causes up to 10% muon neutrino flux depletion at IceCube.

Atmospheric density variations shift resonance energies from 300 MeV to 300-700 GeV.

New resonance effects are crucial for accurate neutrino physics interpretations.

Abstract

Neutrinos produced in the atmosphere traverse a column density of air before being detected at neutrino observatories like IceCube or KM3NeT. In this work, we extend the neutrino flavor evolution in the {nuSQuIDS} code accounting for the varying height of neutrino production and the variable air density in the atmosphere. These effects can lead to sizeable spectral distortions in standard neutrino oscillations and are crucial to accurately describe some new physics scenarios. As an example, we study a model of quasi-sterile neutrinos that induce resonant flavor conversions at neutrino energies of ${O}(300)\text{ MeV}$ in matter densities of $1 \text{ g/cm}^3$. In atmospheric air densities, the same resonance is then realized at neutrino energies of ${O}(300- 700)$~GeV. We find that the new resonance can deplete the $\nu_\mu + \overline{\nu}_\mu$ flux at the IceCube Neutrino Observatory by as much as $10\%$ in the direction of the horizon.