Glossary & Sources

Glossary

Blazar

A galaxy whose supermassive black hole drives a jet pointed almost at us; the first plausible identified source of a cosmic neutrino.

Cascade

A compact shower of particles from a neutral-current interaction or an electron neutrino. Energy well measured, direction poorly.

Charged current

A neutrino interaction mediated by a W boson, turning the neutrino into its charged partner.

Cherenkov radiation

Light emitted when a charged particle moves faster than light does in the surrounding medium.

Cross-section σ

The effective target area a particle presents for an interaction; for neutrinos, fourteen orders of magnitude below a nuclear one.

DOM

Digital Optical Module: the pressure sphere, photomultiplier and electronics frozen into the ice. IceCube has 5,160.

Effective area

The area a perfect detector would need to record what this one actually records, at a given energy and direction.

Flavour

Which charged lepton a neutrino pairs with: electron, muon or tau.

Frank–Tamm formula

Gives the number of Cherenkov photons emitted per unit length per unit wavelength, proportional to sin²θ_c.

Glashow resonance

Formation of a real W boson by an electron antineutrino on an atomic electron, at 6.3 PeV.

Multi-messenger astronomy

Combining neutrinos, photons, cosmic rays and gravitational waves to study one source.

Neutral current

A neutrino interaction mediated by a Z boson; the neutrino survives and only a cascade is seen.

PeV

Petaelectronvolt, 10¹⁵ eV — roughly a thousand times the energy of a proton in the LHC.

Track

The long straight signature of a muon crossing the detector. Direction well measured, energy a lower bound.

Upgoing event

A particle arriving from below, having crossed the Earth — which only a neutrino can do.

The discoveries the prize names

• IceCube Collaboration. “Evidence for High-Energy Extraterrestrial Neutrinos at the IceCube Detector.” Science 342, 1242856 (2013). doi:10.1126/science.1242856Twenty-eight neutrinos above 30 TeV recorded between May 2010 and May 2012, two of them above a PeV — the first significant astrophysical flux.
• IceCube Collaboration et al. “Multimessenger observations of a flaring blazar coincident with high-energy neutrino IceCube-170922A.” Science 361, eaat1378 (2018). doi:10.1126/science.aat1378One track, half a degree of sky, and a dozen other observatories: the first cosmic neutrino with a plausible source.
• IceCube Collaboration. “Observation of high-energy neutrinos from the Galactic plane.” Science 380, 1338 (2023). doi:10.1126/science.adc9818The Milky Way imaged in neutrinos.

The prize

• Press release, Nobel Prize in Physics 2026, NobelPrize.org.
• Nobel Prize in Physics awarded to Francis Halzen for ice research, France 24, 6 October 2026.
• IceCube Neutrino Observatory, University of Wisconsin–Madison.