Nearly 90 years after Wolfgang Pauli proposed its existence, the neutrino remains mysterious. First observed nearly 30 years after its conception, it was another several decades before physicists confirmed that neutrinos have mass, a discovery based on the observation that one type of neutrino, which come in three different “flavors” (electron neutrino, muon neutrino, and tau neutrino), can change into another type after traveling a distance. This “neutrino mixing”, or “oscillation”, is direct evidence that neutrinos have mass -- the two properties are inextricably linked.

Neutrinos outnumber electrons, protons, and neutrons in today’s universe by about a factor of 10,000,000,000. So, it’s easy to imagine how basic properties of the neutrino, like mass and how often it mixes, can have a big impact! The mass of the neutrino and the way it mixes affect how galaxies formed to produce large scale structures in the universe; the mechanism which may have facilitated a universe made out of matter, rather than matter and antimatter in equal parts; heavy element formation in the universe; and our understanding of the underlying symmetries that govern particles and fields.

The current challenge for particle physicists is to elucidate neutrino mass fully and determine exactly how, why, and when the quantum mechanical mixing happens. Toward these tasks, U-M physics graduate student Rory Fitzpatrick has developed new methods for classifying neutrino interactions in vast datasets with her advisor Professor Josh Spitz and Fermilab physicist Tingjun Yang - who are all part of the ArgoNeuT collaboration at Fermilab. They have recently published novel electron neutrino measurements using new pattern recognition strategies for identifying these types of neutrinos in argon-based detectors. These tools, which can help determine how often a muon neutrino turns into an electron neutrino, are critical for future experiments that seek to fully understand neutrino mixing and, in general, how the neutrino has impacted the evolution of the universe. 

The Fermilab News site explains the impact of these measurements in this article.

The actual publication of the measurement can be found here: Physical Review D Rapid Communications.

More Information:

Josh Spitz

Rory Fitzpatrick