Author: Maria Temming / Source: Science News
For the first time, researchers have directly observed an exotic type of radioactive decay called two-neutrino double electron capture.
The decay, seen in xenon-124 atoms, happens so sparingly that it would take 18 sextillion years (18 followed by 21 zeros) for a sample of xenon-124 to shrink by half, making the decay extremely difficult to detect.
The long-anticipated observation of two-neutrino double electron capture, reported in the April 25 Nature, lays the groundwork for researchers to glimpse a yet unseen, even rarer version of this decay: neutrinoless double electron capture.Observing that process would confirm that subatomic particles called neutrinos are their own antimatter particles, which could help resolve the mystery of why our universe is made almost entirely of matter, rather than antimatter (SN: 3/17/18, p. 14).
“It’s been quite the buzz within the community that this result is coming out,” says Lindley Winslow, a physicist at MIT not involved in the work.
Xenon-124 is an isotope, a form of an element having the same number of protons but a different number of neutrons (the number designates the total number of protons and neutrons in the nucleus). It’s one of the few radioactive isotopes that decays via two-neutrino double electron capture. But atoms undergo this decay so rarely that researchers needed to monitor a huge amount of xenon to stand a chance of seeing it.
Particle physicist Christian Wittweg of the University of Münster in Germany and colleagues searched for signatures of two-neutrino double electron capture with the XENON1T detector, a machine typically used to hunt for dark matter. The device, shielded from background radiation in the underground Gran Sasso…
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