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Title: Can nuclear uncertainties bias DUNE and Hyper-Kamiokande CP-phase measurements?
Plain: DUNE (Deep Underground Neutrino Experiment) and Hyper-Kamiokande will compare how neutrinos and antineutrinos change type to look for a difference between matter and antimatter. If the nuclear models wrongly predict how neutrinos and antineutrinos interact, the measured asymmetry could be shifted.
Precise: Determine whether residual cross-section model errors after near-detector constraints (axial form factor, 2p2h, pion production, $\nu$ versus antineutrino and $\nu_e$ versus $\nu_\mu$ differences) shift the fitted $\delta_{\mathrm{CP}}$ by more than its statistical uncertainty at full DUNE and Hyper-Kamiokande exposure. The answer is the size of the bias in degrees for realistic alternative nuclear models, obtained from mock-data studies that use models outside the fitting model's freedom.
Settled by: Mock-data oscillation fits with independent nuclear models, plus near-detector and electron-scattering constraints that reduce the induced $\delta_{\mathrm{CP}}$ bias below the statistical error.
Kind: well-posed
Answer type: value
References: (empty)
Literature status: open
Status note: T2K and NOvA published a first joint oscillation analysis in Nature in 2025; DUNE and Hyper-Kamiokande had not taken beam data as of 2026.
Posed since: (empty)