On Wednesday, a team of researchers announced that they got extremely lucky. The team is building a detector on the floor of the Mediterranean Sea that can identify those rare occasions when a neutrino happens to interact with the seawater nearby. And while the detector was only 10 percent of the size it will be on completion, it managed to pick up the most energetic neutrino ever detected.
For context, the most powerful particle accelerator on Earth, the Large Hadron Collider, accelerates protons to an energy of 7 Tera-electronVolts (TeV). The neutrino that was detected had an energy of at least 60 Peta-electronVolts, possibly hitting 230 PeV. That also blew away the previous records, which were in the neighborhood of 10 PeV.
Attempts to trace back the neutrino to a source make it clear that it originated outside our galaxy, although there are a number of candidate sources in the more distant Universe.
Searching for neutrinos
Neutrinos, to the extent they’re famous, are famous for not wanting to interact with anything. They interact with regular matter so rarely that it’s estimated you’d need about a light-year of lead to completely block a bright source of them. Every one of us has tens of trillions of neutrinos passing through us every second, but fewer than five of them actually interact with the matter in our bodies in our entire lifetimes.
The only reason we’re able to detect them is that they’re produced in prodigious amounts by nuclear reactions, like the fusion happening in the Sun or a nuclear power plant. We also stack the deck by making sure our detectors have a lot of matter available for the neutrinos to interact with.
One of the more successful implementations of the “lots of matter” approach is the IceCube detector in Antarctica. It relies on the fact that neutrinos arriving from space will create lots of particles and light when they slam into the Antarctic ice. So a team drilled into the ice and placed strings of detectors to pick up the light, allowing the arrival of neutrinos to be reconstructed.
Article by:Source: John Timmer
