Accurate Measurement of the Electron Antineutrino Yield of $^{235}$U Fissions from the STEREO Experiment with 119 Days of Reactor-On Data

H. Almazán , L. Bernard (1) , A. Blanchet (2) , A. Bonhomme (2) , C. Buck , P. del Amo Sanchez (3) , I. El Atmani (2) , J. Haser , L. Labit (3) , J. Lamblin (1) , A. Letourneau (2) , D. Lhuillier (2) , M. Licciardi (1) , M. Lindner , T. Materna (2) , A. Minotti (2) , A. Onillon (2) , H. Pessard (3) , J.-S. Réal (1) , C. Roca , R. Rogly (2) , T. Salagnac (1) , V. Savu (2) , S. Schoppmann , V. Sergeyeva (3, 4) , T. Soldner (5) , A. Stutz (1) , M. Vialat (5)

1 LPSC - Laboratoire de Physique Subatomique et de Cosmologie
2 IRFU - Institut de Recherches sur les lois Fondamentales de l'Univers
3 LAPP - Laboratoire d'Annecy de Physique des Particules
4 IPNO - Institut de Physique Nucléaire d'Orsay
5 ILL - Institut Laue-Langevin

We report a measurement of the antineutrino rate from the fission of U235 with the STEREO detector using 119 days of reactor turned on. In our analysis, we perform several detailed corrections and achieve the most precise single measurement at reactors with highly enriched U235 fuel. We measure an IBD cross section per fission of σf=(6.34±0.06[stat]±0.15[sys]±0.15[model])×10-43  cm2/fission and observe a rate deficit of (5.2±0.8[stat]±2.3[sys]±2.3[model])% compared to the model, consistent with the deficit of the world average. Testing U235 as the sole source of the deficit, we find a tension between the results of lowly and highly enriched U235 fuel of 2.1 standard deviations.

Mots clés: Elementary Particles and Fields; antineutrino: nuclear reactor; antineutrino/e: yield; fission; uranium; nuclear reactor: particle source; cross section: measured; experimental results; S067RER

Domaines: Physique des Hautes Energies - Expérience [hep-ex]; Physique Nucléaire Expérimentale [nucl-ex]; Instrumentations et Détecteurs [physics.ins-det]

H. Almazán, L. Bernard, A. Blanchet, A. Bonhomme, C. Buck, et al.. Accurate Measurement of the Electron Antineutrino Yield of $^{235}$U Fissions from the STEREO Experiment with 119 Days of Reactor-On Data. Physical Review Letters, 2020, 125 (20), pp.201801. ⟨10.1103/PhysRevLett.125.201801⟩. ⟨hal-02557671⟩