When not bound up in an atomic nucleus, the neutron decays into a proton, electron and anti-neutrino
in on average about 15 minutes. Detailed measurements of this process – the overall rate, correlations
between neutron spin and final-state particle momenta, etc. – can be used to determine parameters of the
underlying standard model of particle physics. The problem is overconstrained: there are many possible
experimental observables dependent on just a few standard model parameters. The parameters thus
determined can be compared with results of other experiments to test the fundamental theory, possibly
revealing new physics as experimental precision improves. An experiment at LANL, using ultracold
neutrons produced at the LANSCE accelerator, recently produced a world-leading measurement of the
neutron lifetime, with overall uncertainty half that of the previous best measurements. This precision
begins to probe an apparent discrepancy in the fundamental theory that has arisen in a class of nuclear
beta decay measurements. In this talk, I will discuss neutron beta decay experiments, especially neutron
lifetime measurements including the ”UCNtau” effort at Los Alamos National Laboratory, and prospects
for extending the reach of these experiments for more stringent tests of the standard model.
zoom link: https://cern.zoom.us/j/68399739111?pwd=SGErcHBQYmVLWFZTVE9jdm5xSmdEdz09
contact the speaker: sclayton@lanl.gov
François Brun, Matthias Saimpert
