Last week, a team from the IceCube Neutrino Observatory, which is located in the southernmost place on Earth (the Geographic South Pole in Antarctica), announced the highest-energy neutrino ever detected. The event occurred and ended in nanoseconds, but it was enough to trip the sensitive detectors at IceCube.
At a gathering this past week in the Netherlands, the team announced that the latest ultra-high-energy neutrino was a muon neutrino, and its energy levels were simply out of this world.
To clarify, there are three known kinds of neutrinos: Electron neutrinos, muon neutrinos, and tau neutrinos. Ultimately, when muon neutrinos interact, they release a muon. It is this muon that scientists try to detect, and from the data that we gather on it, we can learn about the neutrino that made it.
The energy recorded of this muon was in excess of 2,600 trillion electronvolts (teraelectronvolts, TeV). This breaks the previous record at IceCube, which was set at 2,000 TeV. But where does the neutrino come in? What was its energy?
The team explains, “We have been adding, to our previous analysis, more years of data, and in an extra year we found this spectacular event,” says Francis Halzen, IceCube principle investigator for the University of Wisconsin, Madison. “Utilizing standard model material science, the vitality of this neutrino is some place around 5,000-10,000 TeV, with the in all likelihood esteem some place in the center,” Halzen clarified. “This neutrino packs around 1,000 times the vitality of the LHC shaft. It is terrific.”
In you aren’t aware, neutrinos are subatomic particles with a mass that is close to zero. They are also electrically neutral, and they rarely interact with normal matter. In fact, they are capable of passing through almost all matter without having any sort of interaction with it. They can even pass through entire planets without changing their course.
So then, how were we able to make this detection?
Thousands of sensors are distributed over a cubic kilometer of volume beneath the dense Antarctic ice, and these sensors are set to detect rapid movements of charged leptons (electrons, muons, or taus) that emit Cherenkov radiation. When the particles travel at nearly the speed of light through the ice, they are are detected by the photo multiplier tubes within the digital optical modules that make up the light sensors employed by IceCube.
Ultimately, this structure was created for exactly this purpose: To capture one of the rarest events in the subatomic world—The interaction of a neutrino with matter. And although we didn’t see the neutrino itself, we were able to process the information on it based on what we recorded from the muon as it bumped into an atom. Ultimately, from this data we were able to determine the speed, energy, and source of the neutrino.
Although IceCube, in comparison, detects far fewer neutrinos than traditional telescopes are detecting photons, the ones that are found help give us insight into such things as the cosmic microwave background and other sources of radiation beyond our own galaxy. In many ways, such events open up a whole new world of physics.