The most energetic neutrino - in picture form

This is an event view of the highest energy IceCube neutrino that I mentioned in my last post, as presented at the 2015 International Cosmic Ray Conference.  Each sphere is one optical sensor; the colored spheres show modules that observed light from this event.  The sizes of the spheres show how many photons each module observed, while the color give some idea of the arrival time of the first photon, from red (earliest) to blue (latest).

It is easy to see that the neutrino is going slightly upward (by about 11.5 degrees), so the muon cannot be from a cosmic-ray air shower; it must be from a neutrino.  The fact that the muon comes from just below the horizon is not surprising.  At PeV energies, neutrinos interact more than at lower energies, so the Earth is opaque.  So, we do not expect to see near-vertical upward-going neutrinos with PeV energies.

The measured visible energy is 2.6 +/- 0.15 PeV (1 PeV = 10^{15} eV).  This is the energy actually seen in the detector.  It does not include the energy lost by the muon before it reaches the detector,  the energy carried off by the outgoing muon, or the fraction of the neutrino energy that was transferred into a hadronic shower, rather than the observed muon.  So, the actual neutrino energy is a multiple of this.