Related Experiment Video
Updated: May 4, 2026

High-Resolution Neutron Spectroscopy to Study Picosecond-Nanosecond Dynamics of Proteins and Hydration Water
Published on: April 28, 2022
Improved determination of the neutron lifetime
A T Yue1, M S Dewey2, D M Gilliam2
1Institute for Research in Electronics and Applied Physics, University of Maryland, College Park, Maryland 20742, USA and National Institute of Standards and Technology, Gaithersburg, Maryland 20899, USA and University of Tennessee, Knoxville, Tennessee 37996, USA.
This study refines the neutron lifetime measurement by directly measuring neutron monitor efficiency, reducing uncertainty and improving accuracy. The updated neutron lifetime is 887.7 seconds.
Area of Science:
- Nuclear Physics
- Particle Physics
- Metrology
Background:
- The 2005 neutron lifetime measurement (886.3±1.2[stat]±3.2[syst] s) had dominant uncertainties from neutron beam fluence determination.
- Fluence was measured using a neutron monitor calibrated against 6Li(n,t)4He nuclear data.
Purpose of the Study:
- To directly measure the neutron monitor detection efficiency, independent of nuclear data.
- To improve the precision of the neutron lifetime measurement by reducing systematic uncertainties.
Main Methods:
- Directly measured neutron monitor efficiency using a totally absorbing neutron detector.
- Verified temporal stability of the neutron monitor through ancillary measurements.
- Applied the improved monitor efficiency to the 2005 neutron lifetime data.
Main Results:
- Achieved a fivefold improvement in the uncertainty of the neutron monitor efficiency (0.057%).
- The measured efficiency is consistent with the previously calculated value.
- The updated neutron lifetime is τ(n)=(887.7±1.2[stat]±1.9[syst]) s.
Conclusions:
- Direct measurement of neutron monitor efficiency significantly reduces systematic uncertainty in neutron lifetime determination.
- This improved method provides a more precise value for the neutron lifetime.
- The findings contribute to fundamental physics by refining a key particle property.
Related Concept Videos
Nuclear Stability
To hold positively...
Nuclear Overhauser Enhancement (NOE)
Atomic Nuclei: Types of Nuclear Relaxation
In spin–lattice or longitudinal relaxation, the excited spins exchange energy with the surrounding lattice as they return to the lower energy level. Among several mechanisms that contribute to spin–lattice relaxation, magnetic dipolar interactions are significant. Here, the excited nucleus transfers...
Nuclear Fission
Nuclear Transmutation
NMR Spectrometers: Resolution and Error Correction

