The NIST Beam Neutron Lifetime Experiments

General ILL seminar

organised by College 3

Thursday, 6 March 2025 at 10h00

Seminar room 110-111, ILL 50, 1st floor

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Zoom link : https://ill.zoom.us/j/95356221700?pwd=pYh2lGM7PXMZT9vuQeDEgccE3TnTuj.1
Password : 440316

"The NIST Beam Neutron Lifetime Experiments"

F. E. Wietfeldt 

Tulane University, New Orleans, LA 70118 USA, few@tulane.edu  

Since 1990 a collaboration based at the NIST Center for Neutron Research in Maryland, USA has conducted a program of neutron beta decay lifetime experiments using the beam method. This program uses a quasi-Penning trap and silicon detector to trap and count neutron decay protons, following the method introduced by J. Byrne at the ILL in the 1980's. The 2005 (updated in 2013) NIST measurement is the most precise beam neutron lifetime result reported to date. Since then, ultracold neutron storage experiments, in particular UCNτ at Los Alamos, have reported increasingly precise results with a significantly smaller lifetime. This "neutron lifetime discrepancy", which now stands at 9.8 ± 2.0 s, has been widely discussed, reported in general public media, and has motivated a number of hypothetical exotic physics solutions. I will review the physics of the neutron lifetime and the NIST program, discuss recent work to investigate systematic effects, and describe the new next-generation BL3 experiment that will run at NIST starting in 2027.

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Hanno Filter (College 3 Secretary)

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