Physics Colloquium: Prof. Francis Halzen, University of Wisconsin-Madison


Location: zoom

IceCube: Opening a New Window on the Universe from the South Pole

Prof. Francis Halzen
Wisconsin IceCube Particle Astrophysics Center and Department of Physics
University of Wisconsin–Madison

We will review the scientific motivation and the early R&D that eventually led the IceCube project to transform a cubic kilometer of natural Antarctic ice into a neutrino detector. The instrument detects more than 100,000 neutrinos per year in the GeV to 10 PeV energy range. Among those, we have isolated a flux of high-energy neutrinos of cosmic origin, with an energy density similar to that of high-energy photons and cosmic rays in the extreme universe. We identified their first source: on September 22, 2017, several astronomical telescopes pinpointed a flaring galaxy, powered by an active supermassive black hole, as the source of a cosmic neutrino with an energy of 290 TeV. Archival IceCube data subsequently revealed a flare in 2014-15 of more than a dozen neutrinos from the same direction. Accumulating evidence suggests that the first cosmic ray accelerator belongs to a special class of active galactic nuclei that is responsible for the origin of the highest energy particles in the Universe.

All interested persons are invited to attend remotely—email for information.