You may not know it, but every second, 100 billion extremely tiny, invisible subatomic particles called neutrinos pass through every square inch of your hand. Physicist Mitch Soderberg says the reason you haven’t noticed is because they rarely interact with matter, so most of those neutrinos that travel through your palm and the entire Earth come and go without a trace have before zooming back into the universe.
Neutrinos are produced by nuclear reactions and radioactive decay from sources all around us, including the sun, the atmosphere, nuclear reactors, and particle accelerators.
“We know that neutrinos and their antimatter versions, antineutrinos, were present in the early universe, and we want to know if subtle differences in the way they interact could have led to matter dominating antimatter in the universe says Soderberg, professor and associate chair in physics at the College of Arts and Sciences (A&S).
Nearly 14 billion years ago, a tiny, dense, fiery region of space expanded and cooled to become the universe we know today, an event known as the Big Bang. The Big Bang should have created equal amounts of matter and antimatter, the particles are identical in almost every way, apart from their electrical charge. If this had happened, the particles of matter and antimatter would have annihilated each other, resulting in a universe containing nothing but leftover energy. Instead, a tiny fraction of matter—roughly one particle per billion—could survive.
Understanding how neutrinos — one of the most basic, common, and lightest subatomic particles with mass — interact could hold the key to determining why our universe exists. By studying these interactions, Syracuse researchers hope to understand the answers to really big questions, like why all “things” in the universe, including stars, planets, and people, are made of matter and not antimatter.
Improved neutrino detection
Working with physicists around the world, Soderberg and members of his research group have played a key role in the discovery of historical neutrinos, including a landmark study last year that confirmed there is no evidence for a theorized fourth type of neutrino (the Standard Model states that there are three types of neutrinos – no more and no less).
Now Soderberg, along with physics professor Denver Whittington, will serve as principal investigator on two new grants: one from the National Science Foundation and one from the Department of Energy (DOE) to study neutrinos and improve future detection technologies. Her DOE grant is part of the federal government’s $78 million investment that will fund 58 research projects that will advance new discoveries in high-energy physics.
Physicists analyze neutrinos with detectors such as MicroBooNE, a 170-ton experiment at the Fermi National Accelerator Laboratory (Fermilab) in Batavia, Illinois. These detectors use state-of-the-art technology to record 3D images of neutrino events. Inside Liquid Argon Time Projection Chambers (LArTPC), liquid argon serves both as a target for the neutrinos and as a medium that transports the image of the interaction to custom sensors and electronics that record the data.
“You get nice images of the aftermath of a neutrino hitting an argon atom, which we use as a basis to reconstruct all the details of the interaction and learn more about the properties of the initiating neutrino,” says Soderberg.
Support from the NSF and the DOE will allow Soderberg and Whittington’s group members to collaborate on neutrino experiments at Fermilab, one of the few places on Earth where a focused beam of neutrinos is generated and directed onto a detector can.
A group of researchers from Syracuse University are currently working directly on experiments at Fermilab, while another team is conducting analysis and laboratory work on the Syracuse University campus.
Whittington, whose neutrino research is also supported by an NSF CAREER Award, will leverage this round of NSF funding for his ongoing work on an experiment called NOvA. This project, which involves more than 260 scientists and engineers from 49 institutions in eight countries, is working to acquire precision measurements of neutrino behavior by sending a neutrino beam from Fermilab to a site in Minnesota.
“NOvA has already made world-leading measurements and is ready to provide the first insights into neutrino mysteries such as the fundamental differences between neutrinos and antineutrinos, which the Deep Underground Neutrino Experiment (DUNE) will ultimately investigate with next-generation precision,” says Whittington.
Research and development from these grants will play a critical role in the DUNE project, which is expected to include multiple LArTPCs the size of the physics building, Soderberg says.
The international flagship experiment, hosted by Fermilab, already has more than 1,000 researchers, including physicists from Syracuse University. DUNE will be 1 mile underground in a former gold mine in South Dakota, directly in the path of a neutrino beam emanating from Fermilab, Illinois. By sending neutrinos from Fermilab 800 miles (1,300 km) through the Earth to detectors at the miles-deep Sanford Underground Research Facility, researchers can definitively determine the properties of neutrinos and give researchers insight into how these fundamental particles work.
According to Whittington, the funding will support her investigation of DUNE’s sensitivity to astrophysical neutrino sources such as core-collapse supernovae, which are violent explosions resulting from a star’s rapid collapse at the end of its life, producing neutron stars and black holes.
“Should one occur in our half of the galaxy while the detectors are operating, collecting data on neutrinos from such an event would shed light on the processes that go on during the formation of neutron stars and black holes,” says Whittington.
Sparkling student discovery
Through the educational component of these grants, graduate and undergraduate students will work on everything from detector design and operations at Fermilab and Syracuse to final data analysis and software development.
“Neutrino experiments at Fermilab typically run 24/7 for years, and our group members will take turns with collaborators from around the world supervising the experiments, which we can do here in Syracuse these days, even if the experiment is in Chicago “, says Soderberg. The team will also create an exhibit on particle physics to be displayed at the Museum of Science and Technology in downtown Syracuse.
In addition, the coming year will also usher in a new era of discoveries at Syracuse University, as the campus will now house the prototype “pixel” LArTPC detector developed by colleagues at Lawrence Berkeley National Laboratory and the University of Bern. Lecturers and students will use the sophisticated detector to study cosmic rays, which, like neutrinos, pass the earth constantly and largely unnoticed. Although harmless to humans or other living creatures on the planet, researchers have not been able to pinpoint the source of these mysterious atomic fragments that keep raining down on the planet.
Students interested in practical, international research and exploring the mysteries of neutrinos can learn more by visiting the Experimental Neutrino Physics group website.