Physicists have set a new upper limit on the mass of neutrinos, the mysterious particles that pervade the Universe but remain almost invisible. According to data from the KATRIN experiment (Germany), the neutrino mass does not exceed 0.45 eV – this is half as much as previously thought, and is only a millionth of the mass of the electron.
The main mystery of the neutrino
Neutrinos are one of the most abundant particles in the cosmos. They are born in the interior of stars, in supernova explosions, in nuclear reactors, and even in the interior of the Earth from radioactive decay. Every second, hundreds of billions of these particles pass through every centimeter of our body. But because they have almost no interaction with matter, we don’t feel their effects, and they are also extremely difficult to detect with detectors.
The main mystery of the neutrino is its mass. The standard model of physics suggested that they should be massless, but experiments in recent decades have proven otherwise. In 2015, the Nobel Prize was awarded for the discovery of neutrino oscillations, a phenomenon where particles spontaneously change their “flavor” – electron, muon or tau neutrinos. This was the most important evidence that neutrinos still have mass. But how much mass?
How to measure the invisible?
The KATRIN experiment uses radioactive tritium, an isotope of hydrogen that decays into an electron and an antineutrino. Since neutrinos cannot be “caught” directly, scientists analyze the energy of the electrons produced during its decay. The greater the mass of the neutrino, the less energy is left for the electron.
With 36 million electrons recorded, physicists were able to refine the upper limit on the neutrino mass. The previous record of 0.8 eV has been broken, and now science knows for sure: the mass of the ghost particle is no greater than 0.45 eV.
By the end of 2025, KATRIN plans to refine its measurements. In parallel, other researchers are searching for answers in space, studying relic radiation and the decays of exotic particles. Perhaps it is the neutrino that will be the key to a new revolution in physics – like the discovery of the electron or the Higgs boson once was.
What gives science a refinement of the neutrino mass:
- New physics beyond the Standard Model. If a neutrino has mass, it means that there are unknown mechanisms that explain its nature.
- Unlocking the mysteries of the Universe. Neutrinos may have played a key role in the victory of matter over antimatter after the Big Bang.
- The search for sterile neutrinos. Hypothetical particles that could be a component of dark matter.
One thing is for sure: the neutrino is finally starting to reveal its secrets.
We previously reported on how neutrinos could be formed during black hole mergers.
According to nature.com
