Trade-off between statistics and systematics for a PROSPECT-I absolute flux measurement*

The Precision Reactor Oscillation and Spectrum Experiment (PROSPECT) is a short-baseline reactor antineutrino experiment designed to perform a sterile neutrino oscillation search and make a precise measurement of the neutrino energy spectrum from a compact reactor core, located at the highly enriched High Flux Isotope Reactor (HFIR) at Oak Ridge National Laboratory. In its first phase, PROSPECT demonstrated a superior signal-to-background while operating with minimal overburden, motivating an absolute reactor antineutrino flux measurement at the few percent level that has potential impacts on understanding the reactor antineutrino anomaly and the global flux picture, as well as reactor monitoring with neutrino detectors. This talk will present experimental progress in selecting the optimal fiducialization and run time of PROSPECT data for the flux analysis in order to maximize available statistics from HFIR while minimizing systematic error to achieve a statistical uncertainty below 1%. It will illustrate the statistical trade-offs associated with neutron mobility and leakage into dead detector material. Experimental and analytical procedures used to calculate and minimize the uncertainty on HFIR’s thermal power will also be addressed.