Speaker
Description
Next-generation reactor experiments, such as JUNO, will be providing high-fidelity data at high energies, opening a new window into precision neutrino physics. In this energy range, the summation method, rather than conversion calculations, is the only approach capable of providing informative predictions of the antineutrino spectrum.
A critical nuclear data input that has been traditionally overlooked in summation calculations is the isomeric yield ratio (IYR), that describes the probability that a fission product is produced in a metastable state versus its ground state. This distinction can be critical, as these states often have drastically different decay energies and antineutrino signatures.
Following a 2021 review of all available experimental IYR data, we recently published a study [1] on the impact of these ratios on antineutrino calculations. In that work, we identified a high-priority list of fission products that significantly affect the antineutrino spectrum but lacked any experimental data. Since then, new results have been published, which used advanced mass measurement techniques with a Penning trap and direct ion counting to provide the first-ever experimental IYR data for important nuclides such as $^{100}$Y and $^{100}$Nb [2].
In this work, we study the impact of these new measurements on summation calculations. By replacing the low-fidelity model used in fission yields libraries with these latest experimental results, we show a more realistic prediction of the high-energy region.
[1] Mattera, A., A. A. Sonzogni, E. A. McCutchan, C. J. Sears, and C. Billings. "Isomeric yield ratios of fission products: A missing piece in reactor antineutrino summation calculations." Physical Review C 111, no. 6 (2025): L061601.
[2] Cannarozzo, S. (2025). From scission to metastability: Isomeric yield ratios in fission studies (Doctoral dissertation, Acta Universitatis Upsaliensis).