Reanalysis of the β-ν[over ¯]_{e} Angular Correlation Measurement from the aSPECT Experiment with New Constraints on...

Area of Science:

• Particle Physics
• Nuclear Physics
• Fundamental Symmetries

Background:

• Neutron decay is a fundamental process for studying the weak interaction.
• Precise measurements of decay correlations test the Standard Model of particle physics.

Purpose of the Study:

• To reanalyze the electron-antineutrino angular correlation (a coefficient) in free neutron decay.
• To determine improved limits for the Fierz interference term (b).
• To test the Standard Model by comparing experimental results with theoretical predictions.

Main Methods:

• Reanalysis of proton recoil energy spectra from the aSPECT spectrometer.
• Application of a correlated fit to determine the a and b coefficients.
• Combined analysis with PERKEO III beta asymmetry data.

Main Results:

• The electron-antineutrino angular correlation coefficient (a) was found to be -0.10402(82).
• An improved 90% confidence interval for the Fierz interference term (b) was determined: -0.041 ≤ b ≤ 0.022.
• A combined analysis suggests a finite value for b (b(c) = -0.0181 ± 0.0065), deviating by 2.82 sigma from the Standard Model.

Conclusions:

• The reanalysis confirms the previously measured value of the a coefficient.
• The experiment provides tighter constraints on the Fierz interference term b.
• The combined results hint at a potential deviation from the Standard Model, warranting further investigation.