Improved Neutron Lifetime Measurement with UCNτ

Area of Science:

• Nuclear Physics
• Particle Physics
• Metrology

Background:

• The free neutron lifetime is a fundamental constant in physics.
• Previous measurements have shown discrepancies, necessitating improved precision.
• Understanding neutron decay is crucial for testing the Standard Model of particle physics.

Purpose of the Study:

• To provide a more accurate measurement of the free neutron lifetime.
• To address discrepancies in existing neutron lifetime data.
• To test the consistency of the Standard Model with precise neutron decay data.

Main Methods:

• Utilized the UCNτ apparatus at the Los Alamos Neutron Science Center.
• Stored approximately 38×10^6 ultracold neutrons (UCNs) in a magnetogravitational trap.
• Employed three independent, blinded analyses, including pairing short and long storage times and a global likelihood fit incorporating beta-decay lifetime.

Main Results:

• Achieved a precise measurement of the free neutron lifetime: τn = 877.75 ± 0.28 (stat) +0.22/-0.16 (syst) seconds.
• Demonstrated consistency between different analytical techniques.
• The achieved sensitivity directly probes the impact of recent Standard Model refinements.

Conclusions:

• The improved neutron lifetime measurement offers a stringent test of the Standard Model.
• This result contributes to resolving the neutron lifetime puzzle.
• Further theoretical and experimental work is warranted to fully understand neutron decay processes.