Despite decades of taking measurements, scientists cannot agree on how long neutrons live. Neutrons are stable inside atoms, but on their own they decay in about 15 minutes, more or less, into a few other particles. Exactly how much more or less is the sticking point. Each experiment seems to yield a different answer.
The lack of resolution is frustrating. Understanding the lifetime of the neutron is important not only for knowledge’s sake but also to answer other more fundamental questions about new physics beyond the known particles and processes in the universe, says Jeffrey Nico, who leads a neutron lifetime experiment at the National Institute of Standards and Technology (NIST) in Gaithersburg, Md. “We can’t leave this disagreement just hanging out there.”