The answer to one of the biggest questions in astrophysics may be found deep below the mountain of Gran Sasso in central Italy.
The CUORE (Cryogenic Underground Observatory for Rare Events, and Italian for ‘heart’) experiment aims to find out why the universe is full of matter, when the Big Bang theoretically should have produced equal amounts of matter and antimatter.
The Laboratori Nazionali del Gran Sasso (LNGS), about 120 km from Rome, is the largest underground research centre in the world. Situated below Gran Sasso mountain, it’s well known for particle physics research by the Italian National Institute for Nuclear Physics (INFN). The INFN furthers Italy’s nuclear physics research tradition initiated by the creator of the world’s first nuclear reactor, Enrico Fermi. INFN employs about 5,000 scientists in the fields of subnuclear, nuclear and astroparticle physics whose work is recognised internationally, contributing to numerous research centres worldwide. As well as four national laboratories, the INFN has Sezioni (Sections) in most major Italian universities. The country’s core of particle physics knowledge also has a positive impact on the Italian economy, with the technology and expertise developed by the INFN and its related academic base feeding innovation in the medical and healthcare industry and the technology sector in general. The INFN is also a leading national and international player in the GRID supercomputing network project, and in expanding its use to applications in other scientific fields, e-commerce and culture. Italy will host the Fourth European Nuclear Physics Conference in Bologna in September, and last hosted the three-yearly International Nuclear Physics Conference in 2013 in Florence.
CUORE started in January with a team of 150 scientists from Italy and the United States conducting a five-year experiment to establish whether neutrinos are their own antiparticles, allowing them to transform between a matter and antimatter version of itself. If that is the case, physicists believe heavier neutrinos would have decayed asymmetrically post-Big Bang, producing more matter, rather than antimatter, versions of themselves.
Over time, two neutrinos will naturally decay into two protons, two electrons, and two antineutrinos; however, if neutrinos are their own antiparticle, then very occasionally the two antineutrinos will cancel each other out in a “neutrinoless decay.”
CUORE is designed to detect an extraordinarily rare event known as ‘neutrinoless double-beta decay’ from the natural decay of tellurium dioxide crystals. The experiment takes place as far away as possible from all interference, in a laboratory under nearly a mile of solid rock, and in what scientists have calculated to be “the coldest cubic metre in the universe” a refrigerator-style device cooled to only seven thousands of a degree above absolute zero. Inside the refrigerated area, 19 towers – each containing 52 cube-shaped crystals of tellurium dioxide, totaling 988 crystals with a mass of about 742 kg and totalling some 100 septillion tellurium atoms – are very carefully monitored in search of the tiny temperature spike that would denote a neutrinoless decay.
Researchers predict they should be able to observe at least five neutrinoless decays over the next five years, in a discovery that would not only confirm that neutrinos are their own antiparticles, but also violate the Standard Model’s law of conservation of lepton number.
“It’s a very rare process — if observed, it would be the slowest thing that has ever been measured,” says CUORE member Lindley Winslow, a member of the Laboratory for Nuclear Science, and the Jerrold R. Zacharias Career Development Assistant Professor of Physics at MIT, who led the analysis. “The big excitement here is that we were able to run 998 crystals together, and now we’re on a path to try and see something.”
Should the experiment not detect the desired event, the experiment’s next generation, CUPID, will take its place by monitoring an even greater number of atoms.
“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,” Winslow says. “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.”
(via: MIT, New Atlas, Research Italy)