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2w ago

NOvA–T2K Publish First Joint Neutrino Analysis, Pointing to Possible CP Violation

The work stops short of determining the neutrino mass ordering, keeping definitive conclusions out of reach.

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The world’s first neutrino observation in a hydrogen bubble chamber. It was found November 13, 1970, on this photograph from the Zero Gradient Synchrotron’s 12-foot bubble chamber. The invisible neutrino strikes a proton where three particle tracks originate (lower right). The neutrino turns into a mu-meson, the long center track (extending up and left). The short track is the proton. The third track (extending down and left) is a pi-meson created by the collision. Image credit: Argonne National Laboratory.
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Overview

  • Pooling roughly a decade of data from both long‑baseline experiments, the collaborations report sharpened measurements of neutrino oscillation parameters in Nature.
  • The combined dataset shows a suggestive difference between neutrino and antineutrino oscillations, indicating a possible violation of CP symmetry.
  • Results do not favor normal versus inverted mass ordering, and the CP‑violation interpretation depends on which ordering is ultimately confirmed.
  • Complementary designs boosted sensitivity: NOvA sends a beam 810 km from Fermilab to a 14,000‑ton detector in Ash River, while T2K spans 295 km from J‑PARC to Super‑Kamiokande.
  • Both teams continue taking data and plan updates, with next‑generation experiments expected to deliver decisive tests later this decade.