Extended Data Fig. 9: Antineutrino yield of²³⁵U fission.

Overview of the measured antineutrino flux from pure fission of²³⁵U (highly enriched nuclear fuel) relative to the HM model. For a direct comparison of data from different detectors with different thresholds and resolutions, the quantity of interest is the ratio of the measured to expected cross-sections per fission,σ_f, defined as the integral of antineutrino spectrum multiplied by the IBD cross-section. The measurement by STEREO (0.945 ± 0.021) is the most accurate so far and found to be in excellent agreement with the previous world average of 0.954 ± 0.014 taken from ref. ⁶⁶. For comparison, we also show the measurement from Daya Bay and RENO with commercial reactors (low enriched nuclear fuel, green), although it relies on reactor evolution simulations to separate the contribution of²³⁵U from other isotopes. The size of the error bars corresponds to the total uncertainty of the respective measurement. The uncertainty of the HM model, common to all measurements and not included in the error bars, is illustrated by the width of the grey band, whereas the purple point and band represent the central value and the uncertainty of the new world average, after including our result. All uncertainties shown are at 1σCL.