While some college professors spend their precious summers content with family or basking in the solitude of a small town, Father Paul Nienaber, associate professor of physics at Saint Mary’s University (SMU), is spending his summer working with tiny particles called neutrinos that may hold the answers to the many unexplained mysteries of the universe.
“I’m just excited and grateful to work on this project with a lot of great people,” said Nienaber, who is part of the team of about 120 scientists from across the United States as well as other countries, including Italy and Switzerland, working with neutrinos as part of the MicroBooNE experiment with Fermi National Accelerator Laboratory (Fermilab), the United States’ premier particle physics laboratory. “It’s a great bunch of people. A lot of people on the experiment are people just getting started with their careers,” Nienaber said of his colleagues, who have included SMU student interns during the summers of 2010 to 2012.
Nienaber has been working with MicroBooNE, which is the name for the experiment involving the detection of tiny neutrino particles, since its beginning in 2007, spending his summers near the Fermilab campus outside of Chicago.
To first understand the neutrino, which is a subatomic particle that is electrically neutral, it is important to understand that scientists do not know much about what they are and why they exist. “Remember, the problem with neutrinos is that they are very small, have no charge, no mass, and hardly interact at all,” Nienaber said of the neutrino, which means “little neutral one” in Italian.
Although we cannot see them with the naked eye, neutrinos pass through the earth constantly. Scientists know that neutrinos can be produced through fission, a process that provides a way to detect them and thus study them. “We know that one source for neutrinos on earth is nuclear reactors; they make a lot of neutrinos,” Nienaber explained. “Nuclear reactors are run by a process called fission, which is when a big nucleus splits into smaller nuclei, and sometimes when this split occurs you get neutrinos, and you get lots and lots of fissions in nuclear reactors.”
At Fermilab, Nienaber and his colleagues create neutrinos from particles that have been sped up in the lab. The name of their experiment, MicroBooNE, is also the name of the 30-ton particle detector that is used to detect neutrinos. “We can create neutrinos at Fermilab and send a beam of them towards the MicroBooNE detector,” Nienaber said. It is so fragile that to transport the MicroBooNE across the Fermilab campus, a truck must drive at the speed of 6 mph.
With the use of liquified argon gas, the MicroBooNE detects the debris of the charged particles, some of which are neutrinos, and allows the scientists to be precise in tracking the neutrinos and reconstructing their movement, thus learning more about the tiny particle itself.
For Nienaber and his colleagues, understanding the neutrino and why it exists is the fundamental basis for their research. When the universe came to be, a massive amount of energy was released in the form of light particles, which produce matter and anti-matter in equal amounts when they react with one another. “But we don’t live in a universe that is 50/50 we live in a universe that is all matter,” Nienaber said. “What happened to all of the anti-matter? Where did it all go?”
Nienaber hopes that neutrinos hold the answer for this problem. “Neutrinos are one of the big places where physicists are looking for solutions to [this question],” he said. “[Looking for solutions] is part of what makes us human, which is our curiosity [as humans] to what we are and who we are, and how the universe works.”