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Improved Short-Baseline 235U Antineutrino Oscillation and Energy Spectrum Measurement Using PROSPECT



Hans Mumm, Denis Bergeron, Mark Tyra, Svetlana Nour, Jerome LaRosa, The PROSPECT collaboration


We present a detailed report updating sterile neutrino oscillation and 235U antineutrino spectrum measurement results from the PROSPECT experiment at the highly enriched High Flux Isotope Reactor (HFIR) at Oak Ridge National Laboratory. In 96 calendar days of data taken at an average distance of 7.9 m from the center of the 85 MW HFIR core, the PROSPECT detector has observed more than 50,000 interactions of nu_e produced in beta decays of 235U fission products. New limits on the oscillation of nu_e to a light sterile neutrino have been set by comparing the detected energy spectra of ten reactor-detector baselines between 6.7 and 9.2 meters. Measured differences in energy spectra between baselines show no statistically significant indication of nu_e to sterile neutrino oscillation and disfavor the Reactor Antineutrino Anomaly best-fit point at the 2.2 sigma; confidence level. The reported 235U nu_e energy spectrum measurement shows excellent agreement with energy spectrum models generated via conversion of the measured 235U beta spectrum, with a chi^2/DOF of 27/31. PROSPECT is able to disfavor at 2.8 sigma; confidence level the hypothesis that 235U nu_e are solely responsible for data-model spectrum discrepancies measured at commercial reactor cores; however, the result provides no substantial preference against a data-model deviation similar to that observed by commercial core experiments.
Physical Review D (Particles, Fields, Gravitation and Cosmology)


sterile neutrino, short baseline reactor, 235U, reactor neutrino spectrum


Mumm, H. , Bergeron, D. , Tyra, M. , Nour, S. , LaRosa, J. and , T. (2021), Improved Short-Baseline 235U Antineutrino Oscillation and Energy Spectrum Measurement Using PROSPECT, Physical Review D (Particles, Fields, Gravitation and Cosmology), [online],, (Accessed May 11, 2021)
Created February 3, 2021, Updated April 22, 2021