Researchers Have Seen The "Rarest Event Ever Recorded"

 

Researchers have detected what is being called the "rarest event ever recorded" in the hunt for that most mysterious of particles, dark matter.

 

They accomplished this incredible observation using a dark matter detector known as XENON1T, run by the XENON Collaboration project founded in Italy. It noted the radioactive decay of a xenon-124 atom, a phenomenon that takes incredibly long time. Xenon is a noble gas. This specific type of xenon has a half-life of 18 billion trillion years. That’s more than 1 trillion times than the present age of the universe. The observation is described in detail in Nature.

 

"We really saw this decay happen. It's the longest, slowest phenomenon that has ever been directly witnessed, and our dark matter detector was sensitive enough to detect it," co-author Ethan Brown, an assistant professor of physics at Rensselaer, told in a statement. "It's incredible to have observed this process, and it says that our detector can detect the rarest thing ever recorded."

 

You might be thinking how we were able to detect it if it is such an extremely rare event. The reason is that a half-life is a probabilistic amount. It's the time it takes for precisely half of the "entities" in a sample to decay. So, the time it would take for half of the atoms in a radioactive element like xenon to decay is 18 billion trillion years. It does not mean that such an incident only occurs once in that time.

 

The detector presented 3,500 kilograms (7,716 pounds) of xenon, so it had approximately 17 billion billion billion atoms (1.701×1028) in it. Of those, just a one, only one decayed and the arrangement of the experiment was able to detect it, regardless of not having been designed for this specific task.

 

The decay of a xenon atom occurs through a procedure called two-neutrino double electron capture. Earlier this has been seen in only two other elements, krypton and barium. Here, the xenon nucleus takes two electrons from its nearby electron shell. These electrons interact with two protons, turning them into neutrons and releasing two neutrinos.

 

"Electrons in double-capture are released from the innermost shell around the nucleus, and that generates room in that shell," Brown described. "The remaining electrons fall to the ground state, and we witness this collapse process in our detector."

 

This first direct detection has allowed scientists to enhance the half-life of this particular xenon atom.

 

 

References:

https://www.cnet.com/news/dark-matter-scientists-observe-the-rarest-event-ever-recorded/#:~:text=The%20universe%20is%20almost%2014,takes%20a%20trillion%20times%20longer.&text=The%20XENON1T%20detector%20has%20allowed,radioactive%20decay%20of%20xenon%2D124.

https://www.independent.co.uk/life-style/gadgets-and-tech/news/dark-matter-rarest-ever-event-xenon-half-life-radioactive-discovery-breakthrough-latest-science-a8884896.html