Final Measurement of the U235 Antineutrino Energy Spectrum with the PROSPECT-I Detector at HFIR

Understand

This Letter reports one of the most precise measurements to date of the antineutrino spectrum from a purely U235-fueled reactor, made with the final dataset from the PROSPECT-I detector at the High Flux Isotope Reactor.

• By extracting information from previously unused detector segments, this analysis effectively doubles the statistics of the previous PROSPECT measurement.
• The reconstructed energy spectrum is unfolded into antineutrino energy and compared with both the Huber-Mueller model and a spectrum from a commercial reactor burning multiple fuel isotopes.
• A local excess over the model is observed in the 5MeV to 7MeV energy region.