Final Search for Short-Baseline Neutrino Oscillations with the PROSPECT-I Detector at HFIR

Area of Science:

• Particle Physics
• Nuclear Physics
• Astrophysics

Background:

• The PROSPECT experiment investigates antineutrino disappearance.
• Searches for sterile neutrinos are crucial for understanding neutrino physics.

Purpose of the Study:

• To precisely search for electron antineutrino disappearance.
• To set limits on sterile neutrino mixing at short baselines.

Main Methods:

• Analysis of inverse beta decay neutrino interactions using the PROSPECT-I detector.
• Utilized a complete 2018 data sample from the High Flux Isotope Reactor.
• Reduced backgrounds and enhanced statistical power for improved sensitivity.

Main Results:

• Statistically consistent positron energy spectra across different reactor-detector distances.
• Excluded sterile neutrino existence at 95% confidence level for mass splittings above 3 eV².
• Ruled out the Neutrino-4 experiment's best-fit point at >5 standard deviations.

Conclusions:

• The PROSPECT data excludes sterile neutrino regions previously unexplored by terrestrial experiments.
• The results challenge claims of short-baseline oscillations suggested by the Gallium Anomaly.
• No evidence for sterile neutrinos was found in the analyzed mass splitting range.