What Can the Death of a Neutron Tell Us About Dark Matter?

Space.com | 5/24/2018 | Staff
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(Inside Science) — Exactly how long a neutron lives is currently under debate. Now researchers suggest this mystery could be solved if neutrons sometimes decay into particles of dark matter, the invisible substance thought to make up more than four-fifths of all matter in the universe. A flurry of research is now putting this notion to the test.

Along with the proton and electron, the neutron makes up most of the visible universe. Without neutrons, complex atomic nuclei simply could not be stable.

Nucleus - Neutron - Proton - Electron - Neutrino

But once outside an atomic nucleus, a neutron would decay into a proton, an electron and a neutrino after 15 minutes on average, according to existing data. Although the neutron was discovered more than 80 years ago, the precise value for its average lifetime remains an open question.

There are two different ways to probe the lifetime of neutrons. In one, scientists place ultracold neutrons in a bottle and see how many are left after a certain amount of time. In the other, researchers analyze beams of neutrons to see how many decay into protons over a given space and time.

Beam - Experiments - Neutron - Lifetime - Seconds

Oddly, beam experiments suggest the neutron's average lifetime is about 888 seconds, roughly 9 seconds longer than what bottle experiments do. "When the lifetime of the neutron is measured by two different approaches, and the results differ, we have a crisis -- is our basic understanding of the laws of physics wrong?" said study senior author Benjamín Grinstein, chair of physics at the University of California, San Diego.

After decades of fine-tuning both experimental approaches, physicists "have found no reason to suspect the discrepancy arises from bad measurements," Grinstein said. "We are left with the very real option that we need to consider changing the laws of physics in a fundamental way."

Researchers - Percent

The researchers now suggest that about 1 percent of the...
(Excerpt) Read more at: Space.com
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