The very veryest particle is more than a million times lighter than an electron

Neutrino particles weigh no more than 0.8 Sextiljoenste Kilogram (0.8 times 10^-36) – Less than a millionth of the mass of an electron. This is evident from measurements from the German Katrin experiment. The researchers have this result Thursday in Science Published.

« It is a great publication and a fantastic result, » says professor Paul de Jong of the University of Amsterdam and research institute Nikhef. « We looked forward to these results of the Katrin experiment because it takes the most direct measurement of the neutrinomass. »

Neutrinos are the most common particles in the universe that have mass. Every second billions of neutrinos shoot through us. We don’t notice anything because they are super light and load -free. They arise with, among other things, radioactive decay and in nuclear reactions and in nuclear reactors on earth and in the sun.

Three flavors

The physicist Wolfgang Pauli presented the existence of neutrinos in 1930 and in 1956 they were measured for the first time. There were three ‘flavors’: electron, muon and tau-neutinos. At the beginning of this century, experiments showed that those tastes can change. Something that is only possible if neutrinos have mass. The experiments did not say what the – clearly small – neutrinomass is.

« That neutrinos have mass and that that mass is so small, intrigues enormously, » says De Jong. According to the standard model of particle physics, which describes all known elementary particles and forces, they are mass -free. « You can only explain neutrinomassas within the standard model by adding an extra, still undiscovered particle, » says De Jong. « Another exciting opportunity is that there is new physics. »

The German Katrin experiment has been trying to find out the neutrinomass since 2019 by studying the radioactive scope of tritium. Tritium is an unstable isotope of hydrogen, which broadcasts an electron and a neutrino during science.

This is possible because the known amount of energy that is released during beta trap is distributed over the electron and neutrino. That energy is in the speed and mass of the particles. The electron can never have all the energy, because the neutrino at least claims the energy that corresponds to its mass.

Not easy

By measuring the maximum energy that electrons bring very precisely, you can therefore determine the neutrinomass. That is not easy, partly because only a trillion part of the electrons that has maximum energy. That is why the Katrin experiment consists of a complex arrangement of seventy meters with pure tritium gas.

The precise neutrinomass is not yet known. But after measuring 36 million electrons in 259 measurement days, the researchers have now determined with 90 percent certainty that neutrinos do not weigh more than 0.45 electron volt, or 0.8 sextiljoenste kilograms.

According to De Jong, the Katrin experiment is well on the way to their measurement goal. The researchers eventually expect to have a thousand measurement days. With that they can measure a neutrinomass of 0.3 or even 0.2 electron volt. If neutrinos turn out to be even lighter, new, more sensitive experiments are needed.

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