The Mystery of the Neutron Lifetime
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The mystery of the neutron lifetime:
Nine seconds. An eternity in some scientific experiments; an unimaginably small amount in the grand scheme of the universe. And just long enough to confound nuclear physicists studying the lifetime of the neutron.
The neutron is one of the building blocks of matter, the neutral counterpart to the positive proton. Like many other subatomic particles, the neutron doesn't last long outside of the nucleus. Over the course of about 15 minutes, it breaks apart into a proton, an electron, and a tiny particle called an anti-neutrino.
But how long the neutron takes to fall apart presents a bit of a mystery. One method measures it as 887.7 seconds, plus or minus 2.2 seconds. Another method measures it as 878.5 seconds, plus or minus 0.8 second. At first, this difference seemed to be a matter of measurement sensitivity. It may be just that. But as scientists continue to perform a series of ever-more-precise experiments to evaluate possible issues, the discrepancy remains.
This persistence leads to the possibility that the difference is pointing to some type of unknown physics. It could be revealing an unknown process in neutron decay. Or it could be pointing to science beyond the Standard Model scientists currently use to explain all of particle physics. There are a number of phenomena that the Standard Model doesn't fully explain and this difference could point the way towards answering those questions.
[...] Whatever results this experiment delivers, the work to understand the neutron lifetime will continue. "It's very telling that there are so many attempts to precisely measure the neutron lifetime. That tells you the emotional reaction of scientists to a discrepancy in the field - "I want to explore this!'" said Broussard. "Every scientist is motivated by the desire to learn, the desire to understand."
Journal Reference:
L.J. Broussard, K.M. Bailey, W.B. Bailey, et al. New search for mirror neutron regeneration [open], EPJ Web of Conferences (DOI: 10.1051/epjconf/201921907002)
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