Reactor Antineutrino Directionality Measurement with the PROSPECT-I Detector

The PROSPECT-I detector has several features that enable measurement of the direction of a compact neutrino source. In this paper, a detailed report on the directional measurements made on electron antineutrinos emitted from the High Flux Isotope Reactor is presented. With an estimated true neutrino (reactor to detector) direction of φ = 40.8xB0 ± 0.7xB0 and θ = 98.6xB0 ± 0.4xB0, the PROSPECT-I detector is able to reconstruct an average neutrino direction of φ = 39.4xB0 ± 2.9xB0 and θ = 97.6xB0 ± 1.6xB0. This measurement is made with approximately 48000 Inverse Beta Decay signal events and is the most precise directional reconstruction of reactor antineutrinos to date.