Francis Louis Halzen (born 23 March 1944) is a Belgian particle physicist and Nobel laureate. He is the Hilldale and Gregory Breit Distinguished Professor at the University of Wisconsin–Madison and Director of its Institute for Elementary Particle Physics. Halzen is the Principal Investigator of the IceCube Neutrino Observatory at the Amundsen–Scott South Pole Station in Antarctica, the world's largest neutrino detector which has been operational since 2010.
In 2026, he was awarded the Nobel Prize in Physics "for decisive contributions to the IceCube Neutrino Observatory and the discovery of high-energy neutrinos of astrophysical origin."
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Early life and education
Halzen was born and raised in Belgium. He graduated from the Catholic University of Leuven, with an MSc Physics degree in 1966, a PhD in 1969, then his Agrégé de l'Enseignement Supérieur in 1972. Between 1969 and 1971 he worked as a scientific associate at CERN. Since 1972 he has been a professor at the University of Wisconsin–Madison and the Principal Investigator on the AMANDA and IceCube projects.
Research career
Halzen has been a leading scientist in the development of cosmic ray physics and astroparticle physics since the 1970s. In addition to particle physics he published many early papers on cosmic ray anomalies and quark matter, and on relations between particle physics and cosmic rays, on particles from supernovae and on muon production in atmospheric gamma-ray showers. He has served on various advisory committees, including those for the SNO, Telescope Array and Auger-upgrade experiments, the Max Planck Institutes in Heidelberg and Munich, the ICRR at the University of Tokyo, the US Particle Physics Prioritization Panel and the ApPEC particle astrophysics advisory panel in Europe.
AMANDA
Halzen first learned about attempts by Russian scientists to detect neutrinos in Antarctica, using radio antennas at their Antarctic research station to search for electric sparks resulting from cosmic neutrinos colliding with the ice. After determining these interactions would be too weak to register, in 1987 he started working on the AMANDA project, which proposed burying an array of light sensors deep in the Antarctic ice which is clear, dark, stable, sterile and free of background light. This pilot experiment proved successful; however, their results were marred by interference from cosmic rays as well as air bubbles in the ice. This convinced him that a much larger and deeper array would be needed, and in 2005 the AMANDA project became part of its successor project, the IceCube Neutrino Observatory.
IceCube
Halzen argued for a much larger detector and secured funding from both European and American sources. In 2005, his team began construction of the IceCube project, designed to be 100 times larger than AMANDA, with a total volume of 1 km3 and buried up to a mile and a half deep. After six years of construction, IceCube became fully operational in 2011.
The most important result from IceCube was the clear breakthrough observation of high-energy neutrinos (about 100 times more energetic than the particles accelerated today at the world's most powerful machine, the LHC at CERN) in 2013, from as-yet-unidentified sources outside the Galaxy. This discovery has stimulated the planning and development of even larger neutrino telescopes, both at the South Pole and deep underwater.
In 2026, Francis Halzen, the principal investigator of the project, was awarded the Nobel Prize in Physics "for decisive contributions to the IceCube Neutrino Observatory and the discovery of high-energy neutrinos of astrophysical origin."
Books
With Alan Martin he co-authored Quarks and Leptons: An Introductory Course in Modern Particle Physics (1984), a standard textbook in particle physics.
Awards
1994: Fellow of the American Physical Society
2013: Breakthrough of the Year Award by the journal Physics World for the first-time discovery of cosmic neutrinos beyond the Milky Way
2015: Balzan Prize
2015: Giuseppe and Vanna Cocconi Prize of the European Physical Society
2018: Bruno Pontecorvo Prize for significant contribution to the IceCube detector construction and experimental discovery of high-energy astrophysical neutrinos.
2019: Yodh Prize of IUPAP
2021: Homi Bhabha Medal and Prize of IUPAP and TIFR
2024 Elected to National Academy of Sciences
2026: APS Medal for Exceptional Achievement in Research
2026: Nobel Prize in Physics "for decisive contributions to the IceCube Neutrino Observatory and the discovery of high-energy neutrinos of astrophysical origin”