November 2013

IceCube results show strong evidence for an astrophysical neutrino flux

In November 2013, the IceCube Collaboration announced the discovery of 26 astrophysical neutrinos in addition to Bert and Ernie—significantly more than background expectations. With energies between 30 and 1,200 TeV, these neutrinos were the most energetic ever observed. And though their flavors, directions, and energies were inconsistent with what we would expect from neutrinos produced in Earth’s atmosphere, they did match predictions for neutrinos of extraterrestrial origin. Together, these detections showed strong evidence for an astrophysical neutrino flux. The results were published in Science.

This discovery heralded the beginning of the exploration of the universe with neutrino telescopes and would later be named “Breakthrough of the Year” by Physics World.

The IceCube Lab in March 2013
The IceCube Laboratory at the Amundsen-Scott South Pole Station, in Antarctica, hosts the computers collecting raw data. Due to satellite bandwidth allocations, the first level of reconstruction and event filtering happens in near real time in this lab. Only events selected as interesting for physics studies are sent to UW–Madison, where they are prepared for use by any member of the IceCube Collaboration. Apart from the US flag, the flags from Chile and the Philippines were flying at the Pole in honor of the home countries of the 2012-2013 IceCube winterovers. Credit: Felipe Pedreros, IceCube/NSF