How long can a neutron survive outside an atom?

Enlarge / Los Alamos National Lab, where the work was done. (credit: Los Alamos National Lab)

Fundamental physics, as we've seen, finds itself in a difficult situation. Nothing unexpected has turned up at the Large Hadron Collider. We have phenomena like dark matter and dark energy that are defying explanation. And some of the most exciting ideas that theoreticians are coming up with have steadfastly refused to submit to any form of experimental testing.

On possible route out of this mess is to focus on some of the oddities in the data that we already have. For example, there are a few measurements that seem to show particle behavior that's inconsistent with physics' Standard Model. And there are other cases where two different routes to the same measurement give different results, a possible sign that some new physics is influencing one experimental approach but not another. But before we pursue these oddities, the first step is to confirm that something unexpected is really happening.

This is exactly the situation we have with the decay of neutrons. We have two different ways of measuring the neutron's half-life, and the values they produce disagree by an appreciable amount. To find out whether this disagreement is real, however, we have to up the precision of the measurements. And that's precisely what a large US-Russian collaboration has done.

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