Probing neutrino production in high-energy astrophysical neutrino sources with the Glashow Resonance

The flavor composition of high-energy neutrinos carries important information about their birth. However, the two most common production scenarios, $pp$ (hadronuclear) and $p\gamma$ (photohadronic) processes, lead to the same flavor ratios when neutrinos and antineutrinos cannot be distinguished. The Glashow resonant interaction $\bar{\nu}_e+e^- \rightarrow W^-$ becomes a window to differentiate the antineutrino contribution from the total diffuse neutrino flux, thus lifting this degeneracy. We examine the power of Glashow resonant events in measuring the fraction of the $\bar{\nu}_e$ flux with current IceCube data, and produce projected sensitivities based on the combined exposure of planned Cherenkov neutrino telescopes around the globe. We find that $pp$ and $p\gamma$ can be distinguished at a 2$\sigma$ significance level in the next decades, in both an event-wise analysis and a more conservative statistical analysis, even with pessimistic assumptions on the spectral index of the astrophysical flux. Finally, we consider the sensitivity of future experiments to mixed production mechanisms.