First antineutrino energy spectrum from $^{235}$U fissions with the STEREO detector at ILL
- Almazán, H.
- Bernard, L.
- Blanchet, A.
- Bonhomme, A.
- Buck, C.
- del Amo Sanchez, P.
- El Atmani, I.
- Labit, L.
- Lamblin, J.
- Letourneau, A.
- Lhuillier, D.
- Licciardi, M.
- Lindner, M.
- Materna, T.
- Pessard, H.
- Réal, J.-S.
- Ricol, J.-S.
- Roca, C.
- Rogly, R.
- Salagnac, T.
- Savu, V.
- Schoppmann, S.
- Sergeyeva, V.
- Soldner, T.
- Stutz, A.
- Vialat, M.
DOIAbstract
International audienceThis article reports the measurement of the 235U-induced antineutrino spectrum shape by the Stereo experiment. 43 000 antineutrinos have been detected at about 10 m from the highly enriched core of the ILL reactor during 118 full days equivalent at nominal power. The measured inverse beta decay spectrum is unfolded to provide a pure 235U spectrum in antineutrino energy. A careful study of the unfolding procedure, including a cross-validation by an independent framework, has shown that no major biases are introduced by the method. A significant local distortion is found with respect to predictions around E ν ≃ 5.3 MeV. A Gaussian fit of this local excess leads to an amplitude of A = 12.1 ± 3.4% (3.5σ)
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