New Precision for Neutron Lifetime Measurements



Laboratory set-up for testing the accuracy of the neutron monitor used in the “in-beam” method of measuring neutron lifetime. Image from the NIST Story.

A team of NiST Physical Measurement Laboratory (PML) scientists, with collaborators elsewhere*, has achieved a five-fold reduction in the dominant uncertainty in an experiment that measured the mean lifetime of the free neutron (exceptionally long for an unstable particle), resulting in a substantial improvement of previous results.

That accomplishment, however, has further deepened the puzzling discrepancy between the lifetime values obtained with the technique used by the NIST collaboration and those from collaborations using a very different method, and the PML-led group is preparing to re-run an upgraded version of the entire original experiment to further reduce the uncertainty in the determined lifetime and evaluate the experimental approach. Continue reading