Neutrino Mass Measured with High Precision by KATRIN, Challenging the Standard Model

Researchers have achieved the most precise measurement to date, narrowing the maximum possible mass of the neutrino. The findings, published in *Science*, refine the upper limit of the neutrino's mass, bringing physicists closer to resolving inconsistencies within the Standard Model, the prevailing theory governing subatomic particles. The Standard Model incorrectly predicts that neutrinos should be massless, a contradiction that this research addresses. Understanding neutrinos could provide insights into the universe's evolution, including galaxy clustering and cosmic expansion since the Big Bang. Neutrinos are produced during nuclear reactions and exist in three "flavors," oscillating between them, implying they possess mass, albeit extremely small. The Karlsruhe Tritium Neutrino (KATRIN) experiment was used to achieve this precision. The experiment uses tritium, a hydrogen isotope, which decays into helium, emitting an electron and an antineutrino. By precisely measuring the energy of emitted electrons, scientists indirectly calculated the antineutrino's maximum mass. The team determined the neutrino's mass to be no more than 0.45 electronvolts, a million times lighter than an electron. This improves upon KATRIN's 2022 result of 0.8 electronvolts and is nearly twice as precise. The KATRIN collaboration plans to further refine the measurement using more data. Other experiments, such as Project 8 and the Deep Underground Neutrino Experiment, will also contribute to understanding neutrino mass. Discrepancies between astronomical observations and laboratory calculations suggest the need for physics beyond the Standard Model. This new measurement provides a crucial piece of the puzzle, potentially opening doors to new physics and a deeper understanding of the universe.