Determination of the Neutrino Flavor Ratio at the Astrophysical Source

Understand

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.