Progress on the BL2 beam measurement of the neutron lifetime

Abstract

A precise value of the neutron lifetime is important in several areas of physics, including determinations of the quark-mixing matrix element |Vud|, related tests of the Standard Model, and predictions of light element abundances in Big Bang Nucleosynthesis models. We report the progress on a new measurement of the neutron lifetime utilizing the cold neutron beam technique. Several experimental improvements in both neutron and proton counting that have been developed over the last decade are presented. This new effort should yield a final uncertainty on the lifetime of 1 s with an improved understanding of the systematic effects.

Dark Matter Interpretation of the Neutron Decay Anomaly

“…If the ongoing beam neutron lifetime measurements at NIST (National Institute of Standards and Technology) [38,39] and J-PARC (Japan Proton Accelerator Research Complex) [40,41] yield results which are still in disagreement with the bottle average, perhaps the best way to proceed would be to include a proton detection system in the bottle experiment. With enough precision, such an experiment would be capable of measuring the branching fraction of neutron beta decays independently from the beam experiment.…”

Neutron’s dark secret

“…The fate of the neutron lifetime discrepancy largely depends on the results of the two ongoing neutron lifetime beam measurements: one at the National Institute of Standards and Technology (NIST) 44,45 and the other at the Japan Proton Accelerator Research Complex (J-PARC). [46][47][48] Those two efforts are complementary, since NIST is sensitive to protons from neutron decays, whereas J-PARC measures electrons.…”

Neutron's Dark Secret

“…The fate of the neutron lifetime discrepancy largely depends on the results of the two ongoing neutron lifetime beam measurements: one at the National Institute of Standards and Technology (NIST) [44,45] and the other at the Japan Proton Accelerator Research Complex (J-PARC) [46,47,48]. Those two efforts are complementary, since NIST is sensitive to protons from neutron decays, whereas J-PARC measures electrons.…”