Particle research gets closer to answering why we’re here

Alexandre Sousa, a professor at the University of Cincinnati, helped outline the next decade of global research into neutrino behavior.

They are produced by nuclear fusion reactions in the Sun, nuclear reactors, or radioactive decay in the Earth’s crust or in particle accelerator laboratories. As they travel, they can switch between one of three types, or “flavors,” of neutrinos and back.

But unexpected experimental results have led physicists to suspect there may be another flavor of neutrino, called a sterile neutrino, because it appears to be immune to three of the four known “forces.”

“Theoretically, it interacts with gravity, but it doesn’t interact with other forces, the weak nuclear force, the strong nuclear force, or the electromagnetic force,” Souza said.

Published in a new white paper Journal of PhysicsGSouza and his co-authors discuss experimental anomalies in neutrino exploration that have baffled researchers.

Their collective vision is articulated and faced with science funding options by the Particle Physics Program Priorities Group (P5), whose final report in 2023 provides direct recommendations to Congress on program funding.

“Neutrino physics promises progress on several fronts,” said co-author Jure Zupan, a professor at the University of California, Los Angeles.

In addition to searching for sterile neutrinos, Zupan said physicists are also studying several experimental anomalies — disagreements between data and theory — that they will be able to test in the near future through upcoming experiments. .

One question is why there is more matter than antimatter in the universe if the Big Bang created matter and antimatter in equal measure. Neutrino research could provide answers, Souza said.

“This may not have an impact on your daily life, but we are trying to understand why we are here,” Souza said. “Neutrinos appear to hold the key to answering these very profound questions.”

Sousa is part of one of the most ambitious neutrino projects at Fermi National Accelerator Laboratory, called DUNE, or the Deep Underground Neutrino Experiment. Workers excavated the former Homestake gold mine 5,000 feet underground to install neutrino detectors. Sosa said it takes about 10 minutes for the elevator to reach the detector cave.

The researchers placed the detectors deep underground to protect them from cosmic rays and background radiation. This makes it easier to isolate particles produced in experiments.

“With these two detector modules and the most powerful neutrino beam ever created, we can do a lot of science,” Souza said. “It’s going to be very exciting to have DUNE coming online. It will be the best neutrino experiment ever built.”

The paper is an ambitious undertaking involving more than 170 contributors from 118 universities or research institutes and 14 editors, including Sousa.

“This is a great example of working with a diverse group of scientists. It’s not always easy, but when they come together, it’s a joy,” he said.

Meanwhile, Sousa and UC associate professor Adam Aurisano are involved in another Fermilab neutrino experiment called NOvA, which studies how and why neutrinos change flavors and return. In June, his team reported their latest findings, providing the most precise measurement of a neutrino’s mass to date.

Another major project called Hyper-Kamiokande (or Hyper-K) is a neutrino observatory and experiment being built in Japan.

“This should produce very interesting results, especially when you put them together with DUNE. So the combination of these two experiments will greatly advance our knowledge,” Souza said. “We should have some answers in the 2030s.”