On the non-detection of Glashow resonance in IceCube
  Electron anti-neutrinos at the Glashow resonance (GR, at $E_{\bar \nu_e} \sim 6.3$ PeV) have an enhanced probability to be detected. With three neutrinos detected by IceCube in the (1-2) PeV energy range at present, one would expect that about 1 to 4 GR $\bar\nu_e$ should have been detected. The high-energy $\sim 8.7$ PeV muon neutrino detected by IceCube may not be a GR event. If so, we expect to detect 50 to 70 GR $\bar\nu_e$, then one would have a "missing Glashow-resonance problem". This would suggest (1) that $p\gamma$ interaction rather than $pp$ interaction is the dominant channel to produce the observed IceCube high-energy neutrinos, (2) that multi-pion $p\gamma$ interactions are suppressed, and (3) that the magnetic field and photon energy density in the $p\gamma$ emission region is such that significant $\mu^+$ cooling occurs before decaying, yet $\pi^+$'s essentially do not cool before decaying. 
Sarira Sahu, Bing Zhang
hep-ph astro-ph.HE