A search for neutrinoless double-beta decay turns up some noise-canceling headphones

Under a mountain in Italy, researchers continue to push the boundaries of science with an experiment that could rewrite the Standard Model of particle physics.

Their experiment, known as the Cryogenic Underground Observatory for Rare Events (CURE), which also includes Yale researchers, has now collected two tons of data (the equivalent of two years of data collection if the cube-shaped crystals weighed a ton) in an annual effort called Rare Nuclear Particle Deco.

Standard double-beta decay is already a proven particle process. When this happens, two neutrons, which are non-essential particles in the nucleus of an atom, change into two protons and emit two electrons and two antineutrinos. Antineutrinos are the antimatter counterpart of neutrinos.

Neutrinoless double beta decay is a theoretical process in which no antineutrinos are created. In theory, this would prove that neutrinos and antineutrinos are the same – that the neutrino is its own antiparticle.

In a new study in the journal ScienceCure researchers used their latest dataset to put new limits on how often neutrinoless double beta decay occurs in tellurium atoms. They say it happens no more than once every 50 septillion years — or once every trillion years.

Aiding the researchers’ work was a specially designed algorithm that filtered out extraneous “noise,” vibrations, including the strange sounds of researchers talking nearby, ocean waves hitting the Italian coast, and earthquakes sending seismic shockwaves anywhere in the world. Think noise canceling headphones, but on a much larger scale.

“The focus of this data release is to understand the sources of external vibrations and how to subtract them from our data to better search for extremely rare decays,” said Rena Maruyama, professor of physics and astronomy at Yale Faculty of Arts and Sciences (FAS) and CURE member.

The Corrie site is located at the Gran Sasso National Laboratory in central Italy. The laboratory sits about a mile below the cliff and is surrounded by low-radiation shielding made from lead ingots salvaged from a 2,000-year-old Roman shipwreck.

Even with its noise-canceling setting and savings, the vibration gets through a certain amount of noise.

As part of their ongoing research, the research team installed more than two dozen sensors that measure temperature, sound, vibration and electrical interference near the detector. The scientists matched the information from the sensors with the recorded data, learning which activity in the detector was “noise” and should be ignored. The new algorithm was applied to previously collected and new data from Coover.

The experiment, led by the U.S. Department of Energy’s Lawrence Berkeley National Laboratory and featuring more than 20 research institutions, including Yale, began operations in 2017 after years of planning and development.

Cure will continue its data collection for the rest of this year. Its successor, Cure Upgrade with Particle Identification (Cupid), will then take over the search for neutrinoless double beta decay at the same location.

The COMED team will add improved light sensors to the experiment’s thermal detectors to improve event identification and background discrimination. It will also use enriched molybdenum crystals instead of tellurium.

“The detection of neutrinoless double-beta decay suggests that neutrinos are their own antiparticles, called Majorana particles,” said Carsten Hager, Eugene Higgins Professor of Physics at Yale-Phase, director of Yale’s Wright Laboratory.

“This unique nature of neutrinos may explain the paradox about matter in the universe. The fact that there is more matter than antimatter,” Hedger added. “It will also violate a fundamental principle of the Standard Model of particle physics called the lepton number and provide unequivocal evidence for new physics.”

Yale researchers lead several efforts at Coover and Cupid, including the development of low-energy analysis and the reduction of the muon-induced background. In addition to Maruyama and Hager, the Yale researchers involved in the experiments are research scientist Penny Slocum, postdoctoral researcher Tyler Johnson, and engineer James Wilhelmi, who are in the Department of Physics. Ridge Liu, Maya Moore, and Zach Maraskin, graduate students at the Yale Graduate School of Arts and Sciences. and former graduate student Samantha Kafer.