New experimental half weight limit for elusive neutrinos

Scientists seeking to discover the elusive mass of neutrinos, the small “ghost particles” that can solve some of the universe’s biggest mysteries, announced new limits on how much they can weigh, halving previous estimates.

Since the existence of neutrinos was proposed almost a century ago, scientists around the world have struggled to learn a lot about them.

This is important as Thierry Lacerel, a physicist at the French Committee on Alternative Energy and Atomic Energy, told AFP, as neutrinos “weave threads that connect the infinitely small and infinitely large” as the universe’s most abundant particle.

Its mass “influences the structures that make up the universe,” he added.

These invisible particles have been washed across space since the Big Bang 13.8 billion years ago.

The number of neutrinos there is difficult to understand. Every atom of a cosmos has about 1 billion.

However, they have very little mass and lack of charge, so neutrinos rarely interact with the problem.

For example, trillions of these so-called ghost particles are thought to flow into the human body every second.

This makes studying extremely difficult. But it’s not impossible.

Chasing the ghost

Since 2019, more than 100 scientists from six countries have been hunting neutrinos as part of a Catlin collaboration at the Karlsruhe Institute of Technology in Germany.

In a study published in the journal Science on Thursday, the collaboration announced that neutrino mass cannot exceed 0.45 evolts.

This is less than a billionth of the mass of the protons in the nucleus of every atom.

The new upper limit for neutrino mass is about half of the figures Catlin released in 2022 after its initial measurement.

Catlin uses a large-scale spectrometer to record the attenuation of tritium, a radioactive form of hydrogen that emits both electrons and neutrinos.

These particles rotate around a 70-meter-long (230-foot) structure dominated by a 200-ton spectrometer operating in a vacuum.

Electrons and neutrinos share the energy produced by attenuated tritium. So the trick is to measure the energy of an electron to infer information about neutrinos.

This requires measuring a lot of electrons.

In 2022, we had to measure 6 million.

And it took 36 million to reach more accurate numbers announced Thursday.

“When we’ve collected all the data by the end of the year,” Lacere said the team is measuring around 250 million electrons.

That will become a moment of truth.

The experiments ultimately revealed a “tracing” of neutrinos or determined that their mass was less than 0.3 electron volts, Lacere explained.

Dark Energy

Scientists hope that by pinching a mass of neutrinos, it will help unravel some of the stubborn secrets of the universe.

Despite its incredible lightness, neutrinos are included in several models that attempt to explain dark energy. This is an unknown force that is thought to promote the constant expansion of the universe.

Approximately 95% of the universe is thought to be made up of unknown dark matter as well as dark energy, with only 5% remaining in everything else.

Katrin Collaboration has set up a new detection system called Tristan to search for a new type of neutrino called sterile neutrinos.

These virtual particles do not interact with matter, but have much more mass than regular neutrinos.

Some scientists suggest that these strangely heavy neutrinos may actually be what we know as dark matter.

©2025 AFP