Scientists have long been baffled by the fact that the universe has much more matter than antimatter, despite astrophysics theories suggesting that the Big Bang should have resulted in an equal amount of both. This is one conundrum a multinational team of researchers hopes to figure out through the five-year CUORE experiment.
According to a report from New Atlas, CUORE was named as an acronym for Cryogenic Underground Observatory for Rare Events, and for the Italian word for “heart.” It is located in the Italian National Institute for Nuclear Physics’ Gran Sasso National Laboratories, and as further noted by the Massachusetts Institute of Technology in a news release, the rare event scientists are looking for is a “neutrinoless double-beta decay” from the natural decaying process of tellurium dioxide crystals.
The CUORE observatory’s key feature is a detector housed within a vending machine-sized refrigerator, which is regularly kept at a temperature of 6 millikelvin, or -459.6 degrees Fahrenheit. This supposedly makes it the “coldest cubic meter in the universe,” according to the MIT release. Fifty-two crystals are housed in the detector’s 19 towers, or a total of 988 tellurium dioxide crystals weighing a combined 1,600 pounds. All in all, scientists believe that these crystals add up to about 100 septillion atoms of the tellurium isotope in question.
As scientists had previously theorized that there might have been an unknown process that allowed matter to be far more present than antimatter after the Big Bang, the researchers working on the CUORE experiment are hoping to test the theory that the neutrino is a Majorana fermion, or a chargeless particle that its own antiparticle and is capable of shifting from matter to antimatter or vice versa. Should this theory be proven correct, this could finally answer questions about our universe’s imbalance of matter and antimatter, as heavier neutrinos might have ended up producing more matter than antimatter due to their asymmetrical decay.
It is through the tellurium dioxide experiments at the CUORE observatory that the researchers hope to confirm the theory about neutrinos being their own antiparticles. Neutrinoless double-beta decays are extremely rare events, which begin when stable isotopes emit two protons, two electrons, and two antineutrinos over a period of time. Assuming neutrinos are their own antiparticles, a neutrinoless decay would occur, where the two antineutrinos cancel each other out. These events are so rare that they are believed to take place in a tellurium atom only “once in several septillion years.”
In the two months since the CUORE Observatory has been recording data, researchers were not able to find any proof of neutrinoless decays taking place, as documented in a study published this week in the journal Physical Review Letters. But since the experiments are scheduled to take place over a period of five years, the scientists expect to detect at least five events of this kind, considering that there are millions of atoms in the nearly 1,000 tellurium dioxide crystals in the detectors’ towers.
Assuming the researchers are not able to detect a neutrinoless double-beta decay within the next five years, there still might be some hope. The CUORE observatory team is now working on the “next generation” series of experiments, codenamed CUPID, which will involve another search for the same rare event, but with more atoms to work with. In a statement, MIT professor and CUORE team member Lindley Winslow said that her team plans to work on a third generation CUORE experiment with even more atoms involved before they can conclude that such an event is impossible.
“If we don’t see it within 10 to 15 years, then, unless nature chose something really weird, the neutrino is most likely not its own antiparticle,” said Winslow.
“Particle physics tells you there’s not much more wiggle room for the neutrino to still be its own antiparticle, and for you not to have seen it. There’s not that many places to hide.”