Understanding the Origin of Matter with the CUORE Experiment

Physicists use a detector under an Italian mountain to search for rare nuclear processes to explain why our Universe has more matter than antimatter.

Image courtesy of the CUORE Collaboration.

The Science

There is so much that we do not yet know about neutrinos. Neutrinos are very light, chargeless, and elusive particles that are involved in a process named beta decay and that can help us to understand the origin of matter in Universe. Beta decay is a type of radioactive decay that involves a neutron converting into a proton emitting an electron and an antineutrino. Beta decay is very common– it occurs about a dozen of times per second in a banana. There might also be an ultra-rare kind of beta decay that emits two electrons but no neutrinos. Nuclear physicists around the world are searching for this neutrinoless-double beta decays (NLDBD) in different nuclei. The interest in these decays arises from their potential to reveal unsolved mysteries related to the Universe’s creation of matter. They can also provide hints towards our understanding of the currently unknown mass of neutrinos.

The Impact

The Cryogenic Underground Observatory for Rare Events (CUORE) can search for these rare NLDBD processes using different nuclei. Scientists rely on complementarity among searches using different nuclei to have a better understanding of the underlying physics in the process. Complementarity in physics involves theories that contrast with each other but that both explain part of the same phenomena. CUORE recently searched for NLDBD using a nucleus that had not previously been studied with CUORE, Tellurim-128. The researchers have so far found no evidence for NLDBD. However, they show that the half-life of Tellurim-128 to decay by NLDBD is longer than 3.6 septillion years (ultra-rare decays have very long half-lives). This lower limit is about 30 times higher than those from prior experiments using the same technique. This new search pushes forward scientists’ knowledge on these rare nuclear decays. This opens another path to our understanding of the origin of matter in our Universe.

Summary

CUORE is one of the world-leading experiments searching for extremely rare nuclear processes. Because of the rareness of these processes, CUORE needs a very low-radioactivity environment achieved by using extremely clean materials and by the Gran Sasso Mountain, which shields the experiment from cosmic rays. CUORE consists of almost 1,000 crystals that are kept at a temperature close to absolute zero by a dedicated refrigeration structure. The temperature of the crystals is measured 1,000 times per second, saved to disk, and analyzed to spot the tiny amount of temperature variations caused by the rare decays. Since the beginning of its operation in 2017, CUORE has collected a huge amount of data and it will continue for at least two more years. Researchers expect better results in the search for NLDBD processes on the nucleus Tellurim-128 in the near future. After CUORE, the next-generation experiments have the potential to unravel several nuclear and particle physics mysteries through the exploration of these elusive processes.

Contact

Yury Kolomensky
Lawrence Berkeley National Laboratory and the University of California at Berkeley
[email protected]

Brian Fujikawa
Lawrence Berkeley National Laboratory
[email protected]

Funding

This work was supported by the Department of Energy Office of Science, Office of Nuclear Physics; the National Science Foundation; the Alfred P. Sloan Foundation; the University of Wisconsin Foundation; Yale University; and the Istituto Nazionale di Fisica Nucleare.