Astrophysical Neutrino Production Diagnostics with the Glashow Resonance
  We study the Glashow resonance $\bar{\nu}_e + e^- \rightarrow W^- \rightarrow$ hadrons at 6.3 PeV as diagnostic of the production processes of ultra-high energy neutrinos. The focus lies on describing the physics of neutrino production from pion decay as accurate as possible by including the kinematics of weak decays and Monte Carlo simulations of pp and p$\gamma$ interactions. We discuss optically thick (to photohadronic interactions) sources, sources of cosmic ray nuclei and muon damped sources. Even in the proposed upgrade IceCube-Gen2, a discrimination of scenarios such as pp versus p$\gamma$ is extremely challenging under realistic assumptions. Nonetheless, the Glashow resonance can serve as a smoking gun signature of neutrino production from photohadronic (A$\gamma$) interactions of heavier nuclei, as the expected Glashow event rate exceeds that of pp interactions. We finally quantify the exposures for which the non-observation of Glashow events exerts pressure on certain scenarios. 
Daniel Biehl, Anatoli Fedynitch, Andrea Palladino, Tom J. Weiler,   Walter Winter
astro-ph.HE hep-ph