Determination of the Neutrino Flavor Ratio at the Astrophysical Source

TL;DR

This paper proposes a statistical method to reconstruct astrophysical neutrino flavor ratios with better than 10% accuracy, enabling source differentiation and considering effects like background flux and CP phase.

Contribution

It introduces a new statistical approach for accurately determining neutrino flavor ratios at sources, accounting for uncertainties and source variations.

Findings

Achieving 10% measurement accuracy distinguishes pion and muon-damped sources.

Improved understanding of atmospheric neutrino background is essential.

The analysis considers source variability and leptonic CP phase effects.

Abstract

We discuss the reconstruction of neutrino flavor ratios at astrophysical sources through the future neutrino-telescope measurements. Taking the ranges of neutrino mixing parameters $\theta_{ij}$ as those given by the current global fit, we demonstrate by a statistical method that the accuracies in the measurements of energy-independent ratios $R\equiv\phi (\nu_{\mu})/(\phi (\nu_{e})+\phi (\nu_{\tau}))$ and $S\equiv\phi (\nu_e)/\phi (\nu_{\tau})$ among integrated neutrino flux should both be better than 10% in order to distinguish between the pion source and the muon-damped source at the $3 \sigma$ level. The 10% accuracy needed for measuring $R$ and $S$ requires an improved understanding on the background atmospheric neutrino flux to a better than 10% level in the future. We discuss the applicability of our analysis to practical situations that the diffuse astrophysical neutrino flux arises from different types of sources and each point source has a neutrino flavor ratio varying with energies. We also discuss the effect of leptonic CP phase on the flavor-ratio reconstruction.