Abstract
This Letter reports the first scientific results from the observation of antineutrinos emitted by fission products of ^{235}U at the High Flux Isotope Reactor. PROSPECT, the Precision Reactor Oscillation and Spectrum Experiment, consists of a segmented 4ton ^{6}Li-doped liquid scintillator detector covering a baseline range of 7-9m from the reactor and operating under less than 1m water equivalent overburden. Data collected during 33 live days of reactor operation at a nominal power of 85MW yield a detection of 25 461±283 (stat) inverse beta decays. Observation of reactor antineutrinos can be achieved in PROSPECT at 5σ statistical significance within 2h of on-surface reactor-on data taking. A reactor model independent analysis of the inverse beta decay prompt energy spectrum as a function of baseline constrains significant portions of the previously allowed sterile neutrino oscillation parameter space at 95%confidence level and disfavors the best fit of the reactor antineutrino anomaly at 2.2σ confidence level.
Highlights
This Letter reports the first scientific results from the observation of antineutrinos emitted by fission products of 235U at the High Flux Isotope Reactor
PROSPECT, the Precision Reactor Oscillation and Spectrum Experiment, consists of a segmented 4 ton 6Li-doped liquid scintillator detector covering a baseline range of 7–9 m from the reactor and operating under less than 1 m water equivalent overburden
It has been suggested that these discrepancies indicate incomplete reactor models or nuclear data [12], oscillation of νe to sterile neutrinos [13], or a combination of effects
Summary
Antineutrinos (νe) emitted from the decay of fission products. Absolute νe flux measurements show a ∼6% deficit with respect to recent calculations [6,7], with this deficit appearing to be dependent on the fuel content of nearby reactors [8]. The measured spectrum deviates from model predictions [9,10,11]. It has been suggested that these discrepancies indicate incomplete reactor models or nuclear data [12], oscillation of νe to sterile neutrinos [13], or a combination of effects. The sterile neutrino hypothesis has received particular attention due to its broad potential impact and to existing supporting experimental indications from accelerator and radioactive source neutrino experiments [14,15,16,17,18]. In a schematic of one active plus one sterile neutrino mixing scenario, the oscillation hypothesis predicts reactor νe disappearance due to an eV-scale sterile neutrino described by
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