Novel energy scale calibration strategies for the PROSPECT-II experiment

Nuclear reactors contributed to the first discovery of the elusive neutrino particle and continue to play a significant role in our understanding of neutrino masses and oscillations. The PROSPECT reactor neutrino experiment, the Precision Reactor Oscillation and SPECTrum Experiment, took data at the High Flux Isotope Reactor (HFIR) at Oak Ridge National Laboratory. This work discusses calibration procedures and the establishment of an energy scale model, and details the development of efficient analysis cuts and subsequent selection cut optimization. The precise energy scale calibration and efficient analysis cuts produced a high quality dataset of neutrino interactions of more than 50,000 within a year's data-taking. New limits on the oscillation of sterile neutrinos were set and no statistically significant indication of a potential sterile neutrino was found. The Reactor Antineutrino Anomaly best-fit point was disfavored at 2.5$\sigma$ confidence level. The high precision \uFive~ neutrino spectrum exhibited a spectral deviation with 2.2$\sigma$ confidence level around 5~MeV region in comparison to the Huber-Mueller model prediction, and the hypothesis that \uFive~neutrinos are solely responsible for spectrum discrepancies between model and data obtained at commercial reactor cores was disfavored at 2.4$\sigma$ confidence level.

Given the success of PROSPECT the collaboration is currently in preparation for an upgraded detector, PROSPECT-II, to further expand the physics goals of the program. The new design optimizes the fiducial volume by elimination of dead space previously occupied by internal calibration channels, which in turn necessitates the external deployment. In this dissertation we developed a novel external calibration scheme. We evaluated the expected performance of externally deployed calibration sources using PROSPECT-I data and a well-benchmarked simulation package. The proposed external calibration scheme delivers a compatible energy scale model and achieves comparable performance with the inclusion of an additional AmBe neutron source, in comparison to the previous internal arrangement of PROSPECT-I. Most importantly, the estimated uncertainty contribution from the external energy scale calibration model meets the precision requirements of the PROSPECT-II experiment. This work also investigates the application of a DT neutron generator as a complementary method for liquid scintillator calibration.