Physics Nobel Prize Awarded to Francis Halzen
Physics Nobel Prize Awarded to Francis Halzen
The prize was announced Tuesday, Oct. 6, at 5:45 a.m. ET and was awarded to Halzen “for decisive contributions to the IceCube Neutrino Observatory and the discovery of high-energy neutrinos of astrophysical origin.”
In 1988, Halzen proposed what ultimately became the IceCube Neutrino Observatory, a detector for capturing ghostlike messengers buried 2 kilometers beneath Antarctic ice, opening the world to neutrino astronomy. He has been its principal investigator since 2001.
Neutrinos rarely interact with matter — so rarely that over one billion of them went through your hand as you read this sentence. They travel vast distances in space and through materials without budging, carrying information from high-energy sources in the sky, like black holes and exploding stars. When muon neutrinos, one of the three neutrino “flavors,” do interact with Antarctic ice, they create a track of blue light called Cherenkov radiation. By placing 5,160 light sensors within this ice, IceCube detected 28 high-energy astrophysical neutrinos by 2013 — two years after it began operations.
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Halzen had the audacious idea that you could turn an enormous volume of naturally occurring Antarctic ice into a telescope for neutrinos. He then led the decades-long effort that turned that idea into IceCube, which now provides an extraordinary window on the universe and some of its most distant and energetic phenomena. This prize highlights one of the great recurring stories of physics: When we find a fundamentally new way to observe nature, we often discover entirely new questions that we didn’t previously know how to ask.
Michael Moloney, AIP Chief Executive Officer -
Congratulations to Francis Halzen on receiving the Nobel Prize in Physics for his groundbreaking contributions to the IceCube Neutrino Observatory and the discovery of high-energy neutrinos of astrophysical origin. From the bold idea of using Antarctic ice to detect these elusive particles to the discoveries IceCube has made possible, his work embodies the ambition and curiosity that propel science forward. This recognition celebrates an extraordinary scientific achievement and the enduring drive to push beyond the boundaries of what we know about our universe.
Meredith LeMasurier, Chief Publishing Officer of AIP Publishing
Meet the 2026 Physics Laureate
Halzen’s first job after his Ph.D. was as a scientific associate at CERN, but in 1971 he took on a six-month visiting position at the University of Wisconsin-Madison. He joined the faculty the following year and has spent the rest of his career at the university. Continuing to focus on particle physics, he also spent considerable time visiting experimental centers such as Fermilab and Brookhaven National Laboratory. In the mid-1980s, he became interested in neutrino physics and in 1987 first floated the idea of embedding a detector in Antarctic ice. He recalled, “I gave a talk on the AMANDA concept … just to see if anyone would laugh me off the stage. And then, of course, nobody laughed, so I continued to worry about it.”
AMANDA, the Antarctic Muon and Neutrino Detector Array, was a predecessor project to IceCube that took shape in the 1990s. In his interview, he remembered he was reluctant to lead the effort, saying, “I always thought it was a bad idea … to have a theorist trying to lead an experiment, but actually in practice it worked very well. At different stages, I tried to get rid of this job and it never worked.” Then, in 2001 he became the principal investigator for the follow-on IceCube facility, which was completed in 2011, leading to the physics results that have now secured the Nobel Prize.
2026 Nobel Resources for Physics
By the Laureate
IceCube
Francis Halzen
AIP Conf. Proc. 1304, 268–282 (2010)
https://doi.org/10.1063/1.3527210
Invited Review Article: IceCube: An instrument for neutrino astronomy
Francis Halzen, Spencer R. Klein
Rev. Sci. Instrum. 81, 081101 (2010)
https://doi.org/10.1063/1.3480478
IceCube: Neutrinos Associated with Cosmic Rays
Francis Halzen
AIP Conf. Proc. 1182, 14–21 (2009)
https://doi.org/10.1063/1.3293770
Lectures on High‐Energy Neutrino Astronomy
Francis Halzen
AIP Conf. Proc. 809, 130–163 (2006)
https://doi.org/10.1063/1.2160978
High‐Energy Neutrino Astronomy
Francis Halzen
AIP Conf. Proc. 745, 3–13 (2005)
https://doi.org/10.1063/1.1878392
High energy neutrino astronomy: Towards kilometer-scale detectors
Francis Halzen
AIP Conf. Proc. 558, 43–55 (2001)
https://doi.org/10.1063/1.1370779
10²⁰ eV cosmic ray and particle physics with IceCube
J. Alvarez-Muñiz and F. Halzen
AIP Conf. Proc. 579, 305–314 (2001)
https://doi.org/10.1063/1.1398184
High energy neutrino astronomy and its telescopes
F. Halzen
AIP Conf. Proc. 342, 69–91 (1995)
https://doi.org/10.1063/1.48812
The AMANDA neutrino telescope: Science prospects and performance at first light
Francis Halzen
AIP Conf. Proc. 423, 154–165 (1998)
https://doi.org/10.1063/1.55094
A full acceptance SSC detector: The cosmic-ray connection
Francis Halzen
AIP Conf. Proc. 276, 679–699 (1993)
https://doi.org/10.1063/1.43867
Neutrino Astronomy
Francis Halzen, John Learned, Todar Stanev
Journal: AIP Conference Proceedings
AIP Conf. Proc. 198, 39–51 (1990)
https://doi.org/10.1063/1.39028
Quarks and Leptons: An Introductory Course in Modern Particle Physics
Francis Halzen, Alan D. Martin, Nilotpal Mitra
Journal: American Journal of Physics
Am. J. Phys. 53, 287 (1985)
https://doi.org/10.1119/1.14146
New quark and weak boson signatures at p̄p colliders
F. Halzen and D. M. Scott
AIP Conference Proceedings 68, 273–276 (1980)
https://doi.org/10.1063/1.32393
Direct photons
F. Halzen and D. M. Scott
AIP Conference Proceedings 68, 172–179 (1980)
https://doi.org/10.1063/1.32421
Hadronic production of charmed and other favorite particles
Francis Halzen
Journal: AIP Conference Proceedings
AIP Conf. Proc. 49, 261–280 (1979)
https://doi.org/10.1063/1.31623
About the Science
First detection of high-energy astrophysical neutrinos with IceCube
Gary C. Hill; for the IceCube Collaboration
AIP Conf. Proc. 1666, 040001 (2015)
https://doi.org/10.1063/1.4915550
On the origin of high-energy cosmic neutrinos
Kohta Murase
AIP Conf. Proc. 1666, 040006 (2015)
https://doi.org/10.1063/1.4915555
The H.E.S.S. multi-messenger program: Searches for TeV gamma-ray emission associated with high-energy neutrinos
F. Schüssler; M. Backes; A. Balzer; F. Brun; M. Füssling; C. Hoischen; J-P. Lenain; M. Lorentz; I. Lypova; S. Ohm; D. Parsons; A. Reimer; on behalf of the H. E. S. S. Collaboration
AIP Conf. Proc. 1792, 060006 (2017)
https://doi.org/10.1063/1.4968989
From AIP Publishing staff
By the Laureate
About the Science
IceCube pinpoints an extragalactic neutrino source
Gigantic IceCube tightens limits on theories that predict dark-matter particles
Neutrino messengers originate within our own galaxy
Record-setting cosmic neutrino breaks in a new telescope
Sterile neutrinos give IceCube and other experiments the cold shoulder
The elusive Glashow resonance was observed deep within Antarctic ice
IceCube expands neutrino search to spot fainter signals
Cosmic tau neutrinos uncovered
High-energy neutrinos originate in our own galaxy
Astrophysical high-energy neutrinos
Oral Histories
Oral history with Francis Halzen , interviewed by David Zierler, July 20, 2020
Oral history with Gregory Jaczko , former Chairman of the Nuclear Regulatory Commission, interviewed by David Zierler, Jan, 14, 2020
“Francis Halzen is somebody who — will he ever get one? I don’t know, but — deserves a Nobel Prize for the neutrino observatory in the Antarctic. I mean, it’s certainly the kind of project you could — if they make a significant discovery, you could easily see that becoming a Nobel Prize. I mean, he was a researcher of tremendous quality, and here I was working with him. He was a wonderful person, and I really, really liked him. ...”
Oral history with Katherine Freese , Director of the Weinberg Institute for Theoretical Physics, the Jeff and Gail Kodosky Endowed Chair in Physics at UT Austin, and the Director of the Texas Center for Cosmology and Astroparticle Physics (TCCAP), interviewed by David Zierler, April 23, 2021
“I’m also friends with Francis Halzen. He’s a really great guy. … He helped make IceCube happen, along with many others. Wisconsin is like … I think what they’ve done is just incredible. IceCube is incredible! Have you read the popular- level book Telescope in the Ice by Mark Bowen? The story of getting that experiment to work is something else. One of the hardest things apparently is they had to drill bore holes into the ice by shooting hot water down there. That’s where the kilometer long string of phototube detectors had to go into the ice. Oh, my god. The whole thing … It’s an extreme environment. Operating at the South Pole is a big deal!”
Oral history with David Nygren , interviewed by David Zierler, May 28, 2021
“[In the ’90s,] I became involved with IceCube, with Francis Halzen and company. It was another one of these random walk processes where you step into the woods and see if there’s a path in there. So I worked with Francis — he is delightful to work with. I thought that I could probably help to make a huge jump from the AMANDA array, an acronym for Antarctic Muon and Neutrino Detector Array. They wanted to go for something like a cubic kilometer, far beyond AMANDA’s scale.”
Oral history with Reina Maruyama , interview by David Zierler, Aug. 25, 2020
“With IceCube, you’re using the volume of the ice itself as the detector. As high energy neutrinos come in from the atmosphere, mostly, but stars when they explode produce neutrinos too. So they come into the ice and interact with the molecules of the ice. After neutrinos interact with the ice molecules, they are converted into relativistic electrons or muons. The electrons and muons emit what’s called Cherenkov light as they travel through the ice. We instrument the ice with many, many light sensors and by looking at which sensors saw light and amount of light detected, we reconstruct the energy and direction of where these neutrinos came from.”
Oral history with Charles R. Bentley , interview by Will Thomas, Aug. 6-7, 2008
“Now, there’s a project to bury neutrino detectors, which are really muon detectors. Well they’re really light detectors. Neutrinos mostly pass through the earth without interacting with anything. But occasionally, just by random chance, one will run into a particle in the material that it’s going through, and then it produces a muon, and the muon produces Cerenkov radiation, and the radiation then is detected by these detectors that are buried in the ice at the South Pole. And that project started in the ’90s. The PIs were here at the University of Wisconsin and then the PICO organization was doing the — the holes were drilled by hot water, not taking a core, just so they could emplace these detectors quick before it froze up again. But, in the course of that drilling program, a lot of the work was transferred here to Wisconsin at a physical sciences laboratory, which is an outgrowth of the physics department here. And so the guys who were doing this decided, as long as they were doing that part of the drilling, they might as well bid on the whole drilling contract. And so, after one unsuccessful try, we were successful in some sense. And then they roped me in because they wanted a glaciologist, because I had retired and didn’t have any post-retirement job yet. So, since the year 2000, I’ve been the PI with a full-time engineering staff that does all the work doing the contract ice core drilling.”
Photo Resources
F. Halzen speaks during the - 300: Rossi Prize session
A van used for transportation by IceCube at the South Pole
Gordon Kane, Jacques Weyers, and Francis Halzen
Deployment of a digital optical module (DOM) sensor in IceCube
An ice-tank from the IceTop surface air shower array
Hose reel used for IceCube drilling
AMANDA electronics at the South Pole
ARIANNA prototype station antenna installation
Debugging the prototype ARIANNA neutrino detection station
Book Catalog Records
Quarks and leptons: An introductory course in modern particle physics
Francis Halzen, Alan D. Martin
This self-contained text describes breakthroughs in our understanding of the structure and interactions of elementary particles. It provides students of theoretical or experimental physics with the background material to grasp the significance of these developments.
The telescope in the ice: Inventing a new astronomy at the South Pole
Mark Bowen
The IceCube Observatory has been called the “weirdest” of the seven wonders of modern astronomy by Scientific American. In The Telescope in the Ice, Mark Bowen tells the amazing story of the people who built the instrument and the science involved. Located near the U. S. Amundsen-Scott Research Station at the geographic South Pole, IceCube is unlike most telescopes in that it is not designed to detect light. It employs a cubic kilometer of diamond-clear ice, more than a mile beneath the surface, to detect an elementary particle known as the neutrino. In 2010, it detected the first extraterrestrial high-energy neutrinos and thus gave birth to a new field of astronomy. IceCube is also the largest particle physics detector ever built. Its scientific goals span not only astrophysics and cosmology but also pure particle physics. And since the neutrino is one of the strangest and least understood of the known elementary particles, this is fertile ground. Neutrino physics is perhaps the most active field in particle physics today, and IceCube is at the forefront. The Telescope in the Ice is, ultimately, a book about people and the thrill of the chase: the struggle to understand the neutrino and the pioneers and inventors of neutrino astronomy.
Neutrino hunters: The thrilling chase for a ghostly particle to unlock the secrets of the universe
Ray Jayawardhana
“Detective thriller meets astrophysics in this adventure into neutrinos and the scientists who pursue them For more than eighty years, brilliant and eccentric scientists around the world have been searching for the incredibly small bits of matter we call neutrinos. Trillions of these ghostly particles pass through our bodies every second, but they are so pathologically shy that neutrino hunters have to use Olympic-size pools deep underground and a gigantic cube of Antarctic ice to catch just a handful. Neutrinos may hold the secrets to the nature of antimatter and what the universe was like just seconds after the big bang, but they are extremely elusive and difficult to pin down--much like the adventurous scientists who doggedly pursue them. In Neutrino Hunters, the renowned astrophysicist and award-winning author Ray Jayawardhana takes us on a thrilling journey into the shadowy world of neutrinos and the colorful lives of those who chase them. Demystifying particle science along the way, Jayawardhana tells a detective story with cosmic implications--interweaving the tales of the irascible Casanova, Wolfgang Pauli; the troubled genius Ettore Majorana, who disappeared without a trace; and Bruno Pontecorvo, whose defection to the Soviet Union caused a Cold War ruckus. Ultimately, Jayawardhana reveals just how significant these fast-moving particles are to the world we live in, and why the next decade of neutrino hunting will redefine how we think about physics, cosmology, and our lives on Earth.”
American Physical Society
American Physical Society congratulates the winner of the 2026 Nobel Prize in Physics
Nobel Prize: Neutrinos from Far, Far Away
Francis Halzen and the search for ghost particles
Physical Review Letters: First Observation of PeV-Energy Neutrinos with IceCube
Physical Review Letters: Observation of High-Energy Astrophysical Neutrinos in Three Years of IceCube Data
American Astronomical Society
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IceCube is another example of a major physics project driving a scientific revolution, pursued and brought to fruition through extraordinary imagination, perseverance and skill. Francis Halzen took an exceptional risk in searching for particles that are rarely detected, ultimately opening a new window onto the distant universe.
Associate Editor, Review of Scientific Instruments
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