The international NOvA collaboration presented new results at the Neutrino 2024 conference in Milan, Italy, on June 17. The collaboration has doubled their neutrino data since their last release four years ago, including adding a new low-energy sample of electron neutrinos. The new results are in line with previous NOvA findings but with enhanced precision. The data suggest a preference for the “normal” ordering of neutrino masses, but uncertainties persist around the neutrino’s oscillation properties.
The latest data from NOvA provide a highly precise measurement of the larger splitting between the squared neutrino masses and slightly favor the normal mass ordering. This precision, combined with data from other experiments at nuclear reactors, indicates that the normal ordering is favored at nearly 7:1 odds. While this suggests that neutrinos follow the normal ordering, scientists have not reached the required level of certainty to declare a discovery.
NOvA, managed by the U.S. Department of Energy’s Fermi National Accelerator Laboratory, uses a beam of neutrinos sent from Fermilab to a detector in Minnesota to study neutrino oscillation. The experiment aims to shed light on the ordering of neutrino masses, as current knowledge indicates three neutrino types with different masses, but uncertainties remain about the absolute mass and which is heaviest. Theoretical models propose two possible mass orderings: normal or inverted, with NOvA working to gather more data to solve this mystery.
Despite advancements, ambiguity remains in the solution to neutrino oscillation in the new NOvA results. Physicists lack sufficient data to differentiate between mass ordering and a property called Charge Parity violation, observing oscillations that could fit either mass ordering with varying levels of CP violation. While specific combinations of the properties have been ruled out, more measurements are needed to fully understand neutrino properties.
NOvA, operational since 2014, is set to continue until early 2027, with plans to expand their antineutrino dataset and improve analysis techniques. These efforts not only aim to maximize the experiment’s sensitivity but also pave the way for future experiments seeking to unravel more mysteries surrounding neutrino properties. The collaboration, consisting of over 200 scientists from eight countries, is dedicated to advancing scientific knowledge about neutrinos.
NOvA’s efforts contribute to a broader picture in neutrino physics, collaborating with various experiments to gather multiple measurements to gain a comprehensive understanding. While challenges exist in deciphering neutrino properties, NOvA and other experiments are crucial in collecting valuable data and producing insights that could lead to groundbreaking discoveries in the field. The collaboration’s work is seen as a stepping stone towards unveiling the elusive nature of neutrinos and enhancing scientific understanding of these mysterious particles.
