Neutron Death Mystery Has Physicists Stymied - Scientific American:
"Beam experiments have been going on for more than 30 years, with the leaders in the field located at NIST. Their best, latest beam results, published in 2013, measured the neutron lifetime at 887.7 seconds, plus or minus 3.1 seconds. Bottle experiments, in contrast, go back only about 15 years but have already posted results with higher precision than beam findings. The best result to date from a bottle experiment came in 2008 from a collaboration between the Petersburg Nuclear Physics Institute and the Joint Institute for Nuclear Research in Russia, along with the Institut Max von Laue Paul Langevin (ILL) in France. That team measured the neutron lifetime at 878.5 seconds, plus or minus one second."
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