11-Jun-2018: Scientists in Germany seek to find mass of Neutrinos
Researchers in Germany have started collecting data with a 60 million euro ($71 million) machine designed to help determine the mass of the universe’s lightest particle.
KATRIN’s 200-ton device called a spectrometer will measure the mass of atoms before and after they decay radioactively—thereby revealing how much mass the neutrino carries off. Technicians built the spectrometer about 250 miles from Karlsruhe, Germany, where the experiment will operate.
Researchers say determining the mass of neutrinos is one of the most important open questions in particle physics and will help scientists better understand the history of the universe. Some 200 people from 20 institutions in seven countries are working on the project.
The problem for physicists is that neutrinos are impossible to see and difficult to detect. Any instrument designed to do so may feel solid to the touch, but to neutrinos, even stainless steel is mostly empty space, as wide open as a solar system is to a comet. What’s more, neutrinos, unlike most subatomic particles, have no electric charge—they’re neutral, hence the name—so scientists can’t use electric or magnetic forces to capture them. Physicists call them “ghost particles.”
To capture these elusive entities, physicists have conducted some extraordinarily ambitious experiments. So that neutrinos aren’t confused with cosmic rays (subatomic particles from outer space that do not penetrate the earth), detectors are installed deep underground. Enormous ones have been placed in gold and nickel mines, in tunnels beneath mountains, in the ocean and in Antarctic ice. These strangely beautiful devices are monuments to humankind’s resolve to learn about the universe. It’s unclear what practical applications will come from studying neutrinos.
Scientists working at Sudbury Neutrino Observatory (SNO) discovered in 2001 that a neutrino can spontaneously switch among three different identities—or as physicists say, it oscillates among three flavors. The discovery had startling implications. For one thing, it showed that previous experiments had detected far fewer neutrinos than predicted because the instruments were tuned to just one neutrino flavor—the kind that creates an electron—and were missing the ones that switched. For another, the finding toppled physicists’ belief that a neutrino, like a photon, has no mass. (Oscillating among flavors is something that only particles with mass are able to do.)