In terms of longevity, the universe has nothing for xenon 124.
The theory predicts that the radioactive decay of the isotope has a half-life that goes beyond the age of the universe "with many orders," but no evidence has yet come up for the process.
An international team of physicists, including three researchers from Rice University, assistant professor Christopher Tunnel, visiting scientist Jungji Naganoa and assistant professor Peter Chaginin, announced the first direct observation of a two-time electron capture of two neutrinos for xenon 124, the physical process by which he is falling apart. Their report 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-lasting and essentially stable. Xenon 124 is one of them, although the researchers have calculated its half-life of 160 trillion years when it collapses into tellurium 124. The universe is supposed to be only 13 to 14 billion years.
The new discovery puts the half-life of xenon 124 to 18 sextuple years. (For the record, this is 18,000,000,000,000,000,000,000.)
The half-life does not mean it takes so long that every atom falls apart. The number simply shows how long, on average, it will be necessary to cut most of the radioactive material by half. Still, the chance to see such an Xenon 124 incident is negligible – unless someone collects enough xenon atoms and puts them in the "purest radio space on Earth," Tunnel said.
"A key point here is that we have so many atoms, so if it falls apart, we'll see it," he said. "We have (literal) tone of material."
This place, located deep in the mountain in Italy, is a chamber that contains a ton of purified liquid xenon, protected by radioactive interference in any way.
Called experiment XENON1T, it is the latest in a series of cameras designed to discover the first direct evidence of dark matter, the mysterious substance thought to be the cause of most of the matter in the universe.
It has the ability to observe other unique natural phenomena. One such probe in the last year's mileage was to observe the predicted breakdown of xenon 124. Sorting through the pile of camera-generated data revealed "dozens" of these breakdowns, said Tunnel, who joined Rice this year as part of the University Initiative data science.
"We can see single neutrons, single photons, single electrons," he said. "Everything that goes into this detector will deposit energy in some way, and that's measurable." XENON1T can detect photons that come alive in the liquid medium as well as electrons drawn to the top layer of charged xenon gas. Both are produced when xenon 124 collapses.
"There are different ways a radioactive isotope can break apart," he says. – One of them is beta-decay. That is, an electron comes out. You can have alpha rot where it throws out some of the kernel to release energy. And there is an electronic capture when an electron goes into the nucleus and turns the proton into a neutron. This changes the composition of the nucleus and leads to its disintegration.
"Usually an electron came in and a neutrino came out," said Tunnel. "This neutrinos has a fixed energy that the core ejects its mass. This is a process we often see in nuclear particle physics and is quite well understood. But we have never seen two electrons entering the nucleus at the same time and releasing two neutrinos. "
Photons are released as cascaded electrons to fill the lower free space around the kernel. They appear as a graphics boom, which can only be interpreted as a multiple dual electron capture of two neutrinos. "This can not be explained by other sources of information we know about," said Tunnel, who has been the coordinator for analysis for two years.
XENON1T remains the largest and most sensitive worldwide detector for lightly interactive solid particles, also known as WIMP, the hypothetical particles believed to be dark matter. Tunnel works at XENON1T with a colleague of Rice Naganoa who serves as an operational manager.
Researchers who make up XENON Collaboration, all of whom are co-authors of the paper, have not yet found dark matter but build a larger XENONnT tool for further search. Chaguine is the manager of the new tool responsible for its construction.
The example of cooperation may make researchers discover other non-dark exotic processes, Tunnel said, including the ongoing hunt for another unprecedented process, a neutron neutron neutron neutron. This process, according to the report, "will have consequences for the nature of neutrinos and will give access to the absolute mass of neutrinos."
"It becomes difficult because as long as 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 many students looking for diploma projects, so we do a list of 10 or 20 other measurements – but they're a shot in the dark, and we almost always think of nothing, as is the case with curiosity science.
"In this case, we shot a shot in the dark where two or three students were very lucky," he said.