University of Minnesota
School of Physics & Astronomy


Neutrino Mysteries

Greg Pawloski
Greg Pawloski

Physicists at the University of Minnesota are part of a collaboration that is trying to answer the remaining questions in neutrino physics.

Neutrinos are extremely small particles, about a million times less massive than others in the Standard Model. They also oscillate while they move, which means that they change from one type of neutrino to another. One analogy for this behavior is to imagine a sports car changing into a bus or a van and then back into a sports car as it drives down the highway. Professor Greg Pawloski is one of the leading members of NOVA group which studies the oscillation rate of the neutrinos.

If anti-neutrinos oscillate at a different rate than neutrinos, it could explain the matter/anti-matter asymmetry in the Universe. Physicists believe that the same amount of matter and anti-matter were created during the Big Bang and yet anti-matter has practically vanished from the Universe. If it still existed in the same quantities as matter, the two would annihilate each other and there would be no matter in the Universe. This anti-symmetry has been long-standing mystery in particle physics.

NOVA is a particle detector that uses a beam of neutrinos fired from Fermilab, outside Chicago, through the earth to a far detector that is located above-ground at a research laboratory in Northern Minnesota. There is a near detector at Fermilab, which allows the physicists to compare the changes in particles during their journey.

NOVA announced its first results in August 2015 using less than 10% of its planned data from the detector’s two major channels. There are other experiments that have looked at these two channels and NOVA’s early results are consistent with existing experiments, showing that the detector is on track. NOvA has recently doubled this data sample and is expected to show updated results this summer.

Pawloski was one of the co-leaders of the analysis of the disappearance channel. “You produce a certain number of muon neutrinos and measure how many remain in the far detector. Then you look at them in the far detector, and see how many of them changed into a different flavor and how many disappeared.”

“As it goes on and as we take more data, we’ll become more precise. We’ll be at the forefront with these measurements. In our first results, we took data while building the far detector, at lower power. Now the detector is built, we will be at full power, and we will have data from that soon.”

Pawloski is also getting involved in the DUNE experiment, which is planned to begin taking data in 2023. Similar to NOVA, DUNE will be a neutrino beam from Fermilab that runs to Homestake Gold Mine in South Dakota. Pawloski will be involved with a project to test a prototype of the DUNE detector using a beam at CERN in Switzerland. “DUNE’s detector will be better, its beam more powerful, it will have a longer baseline, and it will make the measurements NOVA is making to an unprecedented precision. If NOVA fails to answer the remaining questions in neutrino physics, DUNE is almost guaranteed to answer them.”