This is an event view of the highest energy neutrino detected so far by the IceCube experiment based at the South Pole (CERN Courier December 2014 p30). Each sphere is one optical sensor; the coloured spheres show those that observed light from this event. The sizes show how many photons each module observed, while the colour gives 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°), so the muon cannot be from a cosmic-ray air shower; it must be from a neutrino. The event, detected on 11 June 2014, was in the form of a through-going muon, which means that the track originated and ended outside of the detector’s volume. So, IceCube cannot measure the total energy of the neutrino, but rather its specific energy loss (dE/dx). While the team is still working on estimating the neutrino energy, the total energy loss visible in the detector was 2.6±0.3 PeV.
• From “Neutrino Hunting in Antarctica” by Spencer Klein, see antarcticaneutrinos.blogspot.ch/.