Physicists have taken a step in opposition to nailing down the mass of the neutrino, most likely probably the most mysterious of all basic debris.
The crew on the Karlsruhe Tritium Neutrino (KATRIN) experiment in Germany stories that neutrinos have a most mass of 0.8 electron volts. Researchers have lengthy had oblique proof that the debris will have to be lighter than 1 eV, however that is the primary time that this has been proven in an instantaneous dimension. The effects have been reported on 14 February in Nature Physics.
The former higher prohibit of one.1 eV used to be reported by way of KATRIN in 2019. The experiment has up to now been ready to position best an higher sure at the mass. However researchers say that it may be able to make a undeniable dimension as soon as it finishes accumulating information in 2024, and is the one experiment on the planet in a position to doing this.
“If the KATRIN experiment used to be to pinpoint a neutrino mass ahead of achieving their sensitivity function of 0.2 eV, it will be extraordinarily thrilling,” says Julia Harz, a theoretical particle physicist on the Technical College of Munich in Germany. Particularly, it will give steering on find out how to reinforce cosmological theories, she provides.
KATRIN weighs neutrinos produced by way of the nuclear decay of tritium, a radioactive isotope of hydrogen. When a tritium nucleus transmutes right into a helium one, it ejects an electron and a neutrino (or, extra correctly, a particle with an equivalent mass referred to as an antineutrino). The neutrino is misplaced, however the electron is channelled right into a 23-metre-long, metal vacuum chamber formed like a Zeppelin airship, the place its power is measured exactly.
The electron carries virtually all the power launched all the way through the tritium’s decay, however some is misplaced with the neutrino. The worth of this shortfall can be utilized to calculate the particle’s mass.
KATRIN’s 2019 effects have been in keeping with an preliminary run of the experiment in April and Might that 12 months, when the tritium beam used to be running at one-quarter of its complete power. The newest result’s in keeping with information from the primary full-strength run, which happened later in 2019. Those information suggest an higher sure of 0.9 eV, which fits all the way down to 0.8 eV when mixed with the sooner effects.
Even supposing the estimate has tightened, it’s nonetheless now not conceivable to file a decrease sure for the neutrino’s mass. The information nonetheless don’t rule out the chance that the mass is 0, says KATRIN member Magnus Schlösser, a particle physicist on the Karlsruhe Institute of Era. However different strains of proof, particularly from cosmological observations, display that the neutrino can’t be massless.
It’s nonetheless conceivable that even after 2024, KATRIN won’t be able to measure the neutrino’s minimal mass: if the mass is lower than 0.2 eV, it will lie out of doors the experiment’s sensitivity.
Schlösser compares the hunt to the Spanish conquistadors’ seek for a legendary town of gold. “It’s like searching for El Dorado,” he says. “You shrink the chance for the place you’ll to find it.”
This newsletter is reproduced with permission and used to be first printed on February 14 2022.