Neutrinos, tiny particles that could hold the key to understanding some of the universe’s biggest mysteries, have seen their weight limit halved. A new experiment by the KATRIN collaboration has set a neutrino mass of 0.45 electron volts, less than a billionth of the mass of a proton.
Scientists have been trying to learn more about neutrinos since they were first proposed nearly a century ago. These particles are abundant in the universe and play a crucial role in shaping its structures. However, their invisibility and lack of interaction with matter make them difficult to study.
To overcome this challenge, over 100 scientists from six countries have been working together since 2019 to measure the decay of tritium, a radioactive form of hydrogen that releases both electrons and neutrinos. The experiment uses a massive spectrometer to record the decay process and measures the energy released by electrons to infer information about the neutrino.
The team’s latest results show that the new upper limit for a neutrino’s mass is around half the figure announced in 2022. This discovery could help unravel several secrets of the cosmos, including dark energy, which is thought to be driving the expansion of the universe.
The KATRIN collaboration plans to set up a new detection system called TRISTAN to hunt for sterile neutrinos, hypothetical particles that do not interact with matter but have much more mass than normal neutrinos. Some scientists believe that these particles could actually be dark matter.
The study’s lead physicist, Thierry Lasserre, noted that the team will measure around 250 million electrons by the end of the year, which could finally uncover a “trace” of the neutrino or determine its mass is less than 0.3 electron volts. This breakthrough could provide valuable insights into the universe and shed light on some of its biggest mysteries.
Source: https://phys.org/news/2025-04-halves-weight-limit-elusive-neutrinos.html