Improved Tensor Current Limit from ^{8}B β Decay Including New Recoil-Order Calculations

Area of Science:

• Nuclear Physics
• Particle Physics

Background:

• Precision beta decay measurements are crucial for testing the Standard Model.
• The Standard Model (SM) predicts specific values for fundamental constants and interactions.

Purpose of the Study:

• To precisely measure the beta-neutrino angular correlation coefficient (aβν) in the β+ decay of Boron-8 (8B).
• To test the Standard Model predictions for weak interactions.
• To constrain the coupling of right-handed neutrinos by combining 8B and 8Li decay data.

Main Methods:

• Utilized the Beta-decay Paul Trap for a high-precision measurement of 8B decay.
• Performed ab initio symmetry-adapted no-core shell-model calculations.
• Combined experimental results with theoretical calculations.

Main Results:

• Determined aβν = -0.3345 ± 0.0019 (stat) ± 0.0021 (syst), the second-most precise value for Gamow-Teller decays.
• Achieved a near factor of 2 improvement in uncertainty for 8B decay.
• Obtained a tight limit on tensor current coupling to right-handed neutrinos.

Conclusions:

• The measured aβν value agrees with the Standard Model prediction of -1/3.
• The results do not support recent findings suggesting a non-zero right-handed neutrino coupling.
• This study enhances the precision of fundamental physics tests using nuclear decays.