Final U235 Antineutrino Spectrum Analysis by PROSPECT-I

The Precision Reactor Oscillation and SPECTrum (PROSPECT) experiment measures the spectrum of antineutrinos from the High Flux Isotope Reactor (HFIR) and searches for potential short-baseline oscillations. The most recent publication by PROSPECT presents a refined analysis that improves upon previous results by including Single Ended Event Reconstruction (SEER) of the previously unused segments, and the careful data splitting (DS) of the different time periods to maximize the available statistics.

The significant increase in statistics and signal to background ratio after applying SEER and DS has provided PROSPECT with one of the most precise measurements of the antineutrino spectrum from a purely U235-fueled reactor. By comparing these measurements with the Huber-Mueller conversion model, a local excess is observed in the 5 MeV to 7 MeV energy region. These results are in concordance with observations from other reactor experiments.The relative size of the excess observed by PROSPECT with respect to that reported from commercial reactor experiments has provided new constraints on the origin of such data-model disagreement.

In this talk, PROSPECT's updated dataset will be discussed together with the unfolding technique used to map reconstructed energy spectrum into antineutrino energy. The main results presented in the latest publication will also be presented, emphasizing their implications in the understanding of current antineutrino spectrum models from nuclear reactors.