Reactor Antineutrino Spectrum Unfolding Techniques for a Final Analysis of PROSPECT-I and Future Experiments*

The Precision Reactor Oscillation and SPECTrum (PROSPECT) experiment measures the spectrum of antineutrinos from the High Flux Isotope Reactor and searches for potential short-baseline oscillations. The analyses performed to produce the last published results from the current dataset (PROSPECT-I) excluded initially unusable data obtained from some detector segments containing non-operating PMTs. Recent efforts from the collaboration have resulted in a more sophisticated analysis that includes the 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 provides the opportunity to extend the physics reach of PROSPECT-I. In this talk, the new methods used to produce a final PROSPECT-I antineutrino energy spectrum will be discussed. In particular, a procedure to jointly unfold the different data periods will be discussed and compared to a single-period unfolding approach, as will plans for interpretation of the resulting spectrum. The multi-period unfolding technique is expected to benefit future multi-experiment joint analyses and multi-reactor spectrum measurements.