If you ever watched the show The Big Bang Theory, then you might remember an episode where Sheldon Cooper and the gang go on a (failed) expedition to Antarctica to discover neutrinos. While their attempts weren’t fruitful on the show, real-life scientists have better luck at finding the very elusive phenomenon. Since operation first began at the IceCube in May 2011, a number of significant discoveries have been made by the observatory. This includes the detection of hundreds of high-energy astrophysical neutrinos, discovering the neutrino flux in 2013 and the first identification of a source of astrophysical neutrinos in 2018.
Science Daily reports a high-energy particle hurtled to Earth from outer space on December 6, 2016, at the speed of light (299, 792, 458 m / s). It was identified as an electron antineutrino. It collided with an electron within the south pole ice-sheet producing a particle that quickly decayed into a shower of secondary particles. The sensors at IceCube Neutrino Observatory picked these up via the massive telescope buried in the Antarctic glacier. The results have been published in the journal Nature this month, years after careful study.
The incident is something called a Glashow resonance event — first proposed by Nobel laureate physicist Sheldon Glashow in 1960 —and is a confirmation of the Standard Model of particle physics. The findings not only confirm Glashow’s predictions but showcase the efficiency of the IceCube.
“When Glashow was a postdoc at Niels Bohr, he could never have imagined that his unconventional proposal for producing the W-minus boson would be realized by an antineutrino from a faraway galaxy crashing into the Antarctic ice,” said Francis Halzen, principal investigator of IceCube from the University of Wisconsin-Madison. The 3-member team involves scientists from Japan and Munich as well but the whole IceCube operation is handled by over 400 people from dozens of countries.
Glashow predicted that an antineutrino could interact with a regular electron and go through the process of resonance to create an undiscovered particle. But it could only happen if the antineutrino had a specific energy threshold. As of now, no human-made colliders are capable of creating particles with such high energy.
But it could happen in supermassive black holes at the centres of galaxies and other extreme cosmic events. Scientists believe such a cosmic event powered the 2016 antineutrino which collided with Earth with an energy of 6.3 PeV (exactly like Glashow’s theory predicted).
Glashow is now an emeritus professor of physics at Boston University.