![]() This is the first time in history that a sub-eV sensitivity in the experiments of this type has been achieved. Using a high-precision spectrometer, the scientists measured the velocities of almost four million electrons, and from this distribution - whose precise shape encodes the neutrino mass - determined the upper limit of its value, which appeared to be smaller than 0.9 eV. They studied the beta decay of an unstable hydrogen isotope called tritium with a short half-life of 12.3 years, which releases an electron and a neutrino among its decay products. This is exactly how physicists from the KATRIN collaboration put new constraints on the neutrino mass. As a result, their mass is usually measured indirectly by studying the velocity distribution of other particles participating in certain interaction or decay processes. Neutrinos are difficult to study because their interactions with other particles are very weak - a single neutrino moving at nearly the speed of light will need a one hundred light year–thick layer of water to get scattered (and therefore detected). Gaining a more precise measurement of the neutrino mass could therefore help shed light on the origin of particle masses. A neutrino’s mass is at least six orders of magnitude smaller than the mass of any other particle we have discovered, and such a huge gap hints that a different mass creation mechanism may be at play. In the Standard Model of particle physics, neutrinos are considered massless, but this non-zero mass challenges our current understanding and hints at a concept called “new physics” - physics beyond the Standard Model that could help clarify some of its discrepancies.Īll massive fundamental particles that we know of - from electrons with mass of half of a megaelectron volt (MeV) to 170 GeV t-quarks - obtain their masses through interactions with the Higgs boson. Neutrinos are abundant in the universe and, despite their small size, play an important role in the evolution of large-scale structures in it, such as galaxy formation.Ī direct laboratory measurement of the neutrino mass would have far-reaching implications in both elementary particle physics and cosmology. It is also extremely tiny-approximately 500,000 times smaller than an electron.Physicists participating in the international Karlsruhe Tritium Neutrino (KATRIN) experiment have just measured the mass of a neutrino with a record-breaking accuracy.Īmong all known subatomic particles with non-zero masses, neutrinos are the lightest with a mass around ten million times less than that of an electron. They found its upper limited to be 1.1 electronvolts, approximately half of the previously determined upper limit. By measuring the energy of the released electron using the spectrometer, they were able to calculate an estimate of the mass of the neutrino to a greater precision than was possible before. When it decays, it emits a single electron and a neutrino at the same time. The researchers used it to study the decay of tritium-a radioactive type of hydrogen. The core piece of equipment used at the site is a 200-ton electron spectrometer. The researchers carried out their work as part of the Karlsruhe Tritium Neutrino Experiment ( KATRIN) on the campus of the Karlsruhe Institute of Technology in Germany. In this new effort, the researchers have taken the third approach. The third method involves attempting to measure the mass of the neutrino directly in ways that do not rely on a theoretical model. The second involves carrying out searches for instances of neutrinoless double-beta decay-an extremely rare event. The first involves studying the cosmic microwave background. To date, scientists have taken three approaches to finding the answer. The next step is to determine their mass. But recent studies have found that not to be the case. ![]() One property of the neutrino in particular that scientists would like to nail down is its mass-until recently, it was thought the tiny particles had no mass at all. Many also believe they hold the key to understanding the early universe, and perhaps physics at its smallest level. They would like to know more about the particles because they are so abundant-scientists believe there are 1 billion times more of them in the universe than atoms. ![]() Neutrinos are mysterious-scientists have found evidence of their existence, but are still struggling to understand their properties. ![]()
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