Physicists from the NOvA collaboration have announced a new result that could improve our understanding of the behavior of neutrinos.
NOvA detector. Image credit: Louise Suter / NOvA Collaboration.
Neutrinos are tiny, nearly massless subatomic particles that travel at near-light speed.
They have previously been detected in three types, called flavors – muon, tau and electron. They also exist in three mass states, but those states don’t necessarily correspond directly to the three flavors.
Neutrinos relate to each other through a complex process called mixing, and the more we understand about how the flavors and mass states connect, the more we will know about these mysterious particles.
NOvA scientists have seen evidence that one of the three neutrino mass states might not include equal parts of muon and tau flavor, as previously thought.
Physicists refer to this as ‘nonmaximal mixing,’ and NOvA’s preliminary result is the first hint that this may be the case for the third mass state.
“Neutrinos are always surprising us. This result is a fresh look into one of the major unknowns in neutrino physics,” said NOvA co-spokesperson Dr. Mark Messier, from Indiana University.
The NOvA experiment has been collecting data on neutrinos since February 2014.
NOvA uses powerful beam of muon neutrinos, generated at the U.S. Department of Energy’s Fermi National Accelerator Laboratory, which travels through the Earth 500 miles to a building-size detector in northern Minnesota.
NOvA was designed to study neutrino oscillations, the phenomenon by which these particles ‘flip’ flavors while in transit.
The NOvA detector is sensitive to both muon and electron neutrinos and can analyze the number of muon neutrinos that remain after traveling through the Earth and the number of electron neutrinos that appear during the journey.
The NOvA experiment’s result shows an equal possibility that the third neutrino mass state is dominated by either muon or tau flavor. Image credit: NOvA Collaboration.
The new data also show that the third mass state might have more muon flavor than tau flavor, or vice versa.
The NOvA experiment hasn’t yet collected enough data to claim a discovery of nonmaximal mixing, but if this effect persists, scientists expect to have enough data to definitively explore this mystery in the coming years.
The scientists presented their results today at the International Conference on High Energy Physics in Chicago.
“The data sample reported today is just one-sixth of the total planned, and it will be exciting to see if this intriguing hint develops into a discovery,” said NOvA scientist Dr. Gregory Pawloski, from the University of Minnesota.
