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Survey: Elemental old-timer makes the universe look like a little one –


As far as longevity is concerned, the universe has nothing to do with xenon 124.

Theory predicts that the radioactive decay of isotopes has a half-life that exceeds the age of the universe "of great size," but until now there was no evidence of the process.

An international team of physicists including three Rice University researchers – assistant professor Christopher Tunnell, visiting scientist Junji Naganoma and assistant researcher Petr Chaguine – reported the first direct observation of the dual neutron capture of xenon electrons 124, the physical process by which it decays. Their document appears this week in the magazine Nature.

While most xenon isotopes have a half-life of less than 12 days, some are considered to be extremely long-lived and substantially stable. Xenon 124 is one of those, although researchers have estimated its half-life of 160 trillion years when it decays into telur 124. Space is assumed to be only 13 to 14 billion years old.

A new finding suggests that the half-life of Xenon 124 is closer to 18 sextillion years. (For the record it is 18,000,000,000,000,000,000.)

The half-life does not mean that it takes a long time for the decay of each atom. The numbers simply show how long, on average, most of the radioactive material will be halved. However, the possibility that the Xenon 124 could experience such an event is still missing if we do not collect enough xenon atoms and place them in the "most radio-pure space on Earth," Tunnell said.

"The key point here is that we have so many atoms, if we do, we will see," he said. "We have (literally) a ton of material."

This place, which is deep within the mountain in Italy, is a chamber containing a ton of highly refined liquid xenon, protected in all possible ways against radioactive disorders.

The XENON1T is the latest in a series of rooms designed to search for the first direct evidence of a dark matter, a mysterious substance that is supposed to represent the majority of matter in space.

It also has the ability to observe other unique natural phenomena. One of these probes during the last year was the monitoring of the predicted decay of xenon 124. The sorting by pile of data generated by the chamber revealed "dozens" of these disintegrations, said Tunnell, who joined Rice this year as part of the company. university initiative Data Science.

"We can see individual neutrons, individual photons, individual electrons," he said. "Anyone entering this detector will in some way deposit energy and be measurable." Both are produced when the xenon 124 decays.

"There are different ways in which the radioactive isotope can collapse," he said. One is beta decay. That means an electron comes. You can have alpha decay, where spits part of the core to release energy. And there is the capture of electrons when the electron goes into the nucleus and changes the proton into the neutron. This changes the composition of the core and causes its decay.

"Normally you have one electron and one neutrino comes out," Tunnell said. "This neutrino has fixed energy, so the core disappears its mass. This is a process that we often see in the physics of nuclear particles and is very well understood. But we have never seen two electrons that arrive at the core simultaneously and emit two neutrons. "

Photons are released as cascades of electrons to fill lower jobs around the core. They appear as a coat on a graph, which can only be interpreted as a multiple double electron capture of two neutrons. "It can not be explained by any other background source we know," said Tunnell, who was a coordinator for analysis for two years.

XENON1T remains the largest and most sensitive detector for weakly interactive massive particles, called WIMPs, hypothetical particles that are considered to be a dark matter. Tunnell worked at XENON1T with colleague Rice Nagano, who was the head of operations.

Researchers who make up XENON Collaboration, all co-authors on paper, have not yet detected dark matter, but the larger instrument, XENONnT, is being built for further search. Chaguine is the head of the new instrument responsible for its construction.

An example of cooperation could lead researchers to find other exotic processes that are not related to the dark matter, said Tunnell, including the ongoing hunting for another invisible process, a neutral double-ended capture in which they do not release neutrinos. This process, according to the article, "would have consequences for the nature of the neutrino and give access to the absolute neutrino mass."

"It's complicated, because while we have the science we are trying to do, we need to think about what we can do with the experiment," he said. "We have a lot of students looking for projects, so we make a list of 10 or 20 other measurements – but the images are in the dark, and almost always we find nothing that is characteristic of curiosity. science.

"In this case, we shot in the dark, where two or three students were lucky," he said.

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