DUNE

Background. Long-baseline accelerator experiments such as T2K and NOvA had hinted at the answers to two of the field’s largest questions, the mass ordering and whether neutrinos and antineutrinos oscillate differently, but neither could reach a decisive result alone. DUNE was conceived as a flagship designed from the start to settle both, building on decades of oscillation measurement.

Objective. Determine the neutrino mass ordering and search for leptonic CP violation, while also serving as a supernova and proton-decay observatory.

Method. A high-intensity neutrino beam produced at Fermilab travels 1,300 km through the Earth to giant liquid-argon time-projection chambers situated about a mile underground at the Sanford Underground Research Facility in South Dakota. Liquid argon records charged-particle tracks in fine three-dimensional detail, letting the experiment reconstruct interactions with precision. A near detector measures the beam before it has a chance to oscillate, controlling systematic uncertainties. The long baseline deliberately maximises the matter effect, the way neutrinos passing through dense rock have their oscillations modified, which is what reveals the ordering.

Status. The facility is under construction, with the first detector modules and beamline being installed and operations expected later this decade. Early physics will build up as additional modules come online.

Significance. Comparing neutrino and antineutrino beams lets DUNE probe whether the mass ordering is normal or inverted and whether the lepton sector violates CP symmetry, a finding that would bear on why the universe contains more matter than antimatter. Together with Hyper-Kamiokande and JUNO it is meant to complete the oscillation picture over the coming years.