Joint Measurement of the <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:mmultiscripts><mml:mrow><mml:mi mathvariant="normal">U</mml:mi></mml:mrow><mml:mprescripts/><mml:none/><mml:mrow><mml:mn>235</mml:mn></mml:mrow></mml:mmultiscripts></mml:mrow></mml:math> Antineutrino Spectrum by PROSPECT and STEREO
H. Almazán, M. Andriamirado, A. B. Balantekin, H. R. Band, C. D. Bass, Denis E. Bergeron, L. Bernard, Adrien Blanchet, A. Bonhomme, N. S. Bowden, C. D. Bryan, C. Buck, T. Classen, Andrew Conant, G. Deichert, P. del Amo Sanchez, Andrea Delgado, M. V. Diwan, M. J. Dolinski, I. El Atmani, Anna Erickson, B. T. Foust, J. K. Gaison, A. Galindo-Uribarri, C. E. Gilbert, S. Hans, A. B. Hansell, K. M. Heeger, B. Heffron, D. E. Jaffe, S. Jayakumar, Xiangpan Ji, D. Jones, J. Koblanski, O. Kyzylova, L. Labit, J. Lamblin, C. Lane, T. J. Langford, J. LaRosa, A. Letourneau, D. Lhuillier, M. Licciardi, M. Lindner, B. R. Littlejohn, X. Lu, J. Maricic, T. Materna, M. P. Mendenhall, A. M. Meyer, R. Milincic, P. E. Mueller, H. P. Mumm, J. Napolitano, R. Neilson, J. A. Nikkel, S. Nour, J. L. Palomino, H. Pessard, D. A. Pushin, X. Qian, J. S. Réal, J. S. Ricol, C. Roca, R. Rogly, R. Rosero, T. Salagnac, V. Savu, S. Schoppmann, M. Searles, V. Sergeyeva, T. Söldner, A. Stutz, P. T. Surukuchi, M. A. Tyra, R. L. Varner, D. Venegas-Vargas, M. Vialat, P. Weatherly, C. White, J. Wilhelmi, A. Woolverton, M. Yeh, C. Zhang, Xianyi Zhang
Abstract
The PROSPECT and STEREO collaborations present a combined measurement of the pure $^{235}\mathrm{U}$ antineutrino spectrum, without site specific corrections or detector-dependent effects. The spectral measurements of the two highest precision experiments at research reactors are found to be compatible with ${\ensuremath{\chi}}^{2}/\mathrm{ndf}=24.1/21$, allowing a joint unfolding of the prompt energy measurements into antineutrino energy. This ${\overline{\ensuremath{\nu}}}_{e}$ energy spectrum is provided to the community, and an excess of events relative to the Huber model is found in the 5--6 MeV region. When a Gaussian bump is fitted to the excess, the data-model ${\ensuremath{\chi}}^{2}$ value is improved, corresponding to a $2.4\ensuremath{\sigma}$ significance.