First antineutrino energy spectrum from ²³⁵U fissions with the STEREO detector at ILL ^*

H. Almazán, L. Bernard, Adrien Blanchet, A. Bonhomme, C. Buck, P. del Amo Sanchez, I. El Atmani, L. Labit, J. Lamblin, A. Letourneau

Abstract

This article reports the measurement of the $^{235}$U-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 $^{235}$U 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 $E_\nu \simeq 5.3$ MeV. A gaussian fit of this local excess leads to an amplitude of $A = 12.1 \pm 3.4\%$ (3.5$\sigma$).

Locations

• arXiv (Cornell University) - View - PDF
• HAL (Le Centre pour la Communication Scientifique Directe) - View
• DataCite API - View
• Journal of Physics G Nuclear and Particle Physics - View