The depths of the Antarctic IceCube, the place where the check was made.
A high-energy particle detector from space located under the ice of the South Pole, experimentally tested a 60-year-old physical theory.
On 6 December 2016 the a The electronic antineutrino rushed to Earth from space near the speed of light carrying 6.3 petaelectron volts (PeV) of energy. Deep in the South Pole ice sheet, it crashed into an electron and produced a particle that rapidly decayed into a shower of secondary particles. The interaction was captured by a huge telescope buried in the Antarctic glacier, the IceCube Neutrino Observatory.
IceCube had witnessed a Glashow resonance event, a phenomenon predicted by the Nobel Prize-winning physicist Sheldon Glashow in 1960. With this detection, scientists provided another confirmation of the standard model of particle physics. It also further demonstrated the ability of IceCube, which detects nearly massless particles called neutrinos using thousands of sensors embedded in Antarctic ice, to perform fundamental physics. The result was published months ago in the journal Nature.
Sheldon Glashow first proposed this resonance in 1960 when he was a postdoctoral fellow at what is now the Niels Bohr Institute in Copenhagen, Denmark. There he wrote an article in which he predicted that an antineutrino (the antimatter twin of a neutrino) could interact with an electron to produce a particle not yet discoveredif the antineutrino had the right energy, through a process known as resonance.
The IceCube Laboratory at the South Pole. This building houses the computer servers that collect data from IceCube sensors under the ice. Photo: DPA
When the proposed particle, the W bosonfinally discovered in 1983, it turned out to be much heavier than Glashow and colleagues expected in 1960. The Glashow resonance would require a neutrino with an energy of 6.3 PeV, nearly 1,000 times more energetic than it is capable of. produce the Large Hadron Collider at CERN. In fact, no man-made particle accelerator on Earth, current or planned, could create a neutrino with that much energy.
But what about a natural accelerator in space? the huge energies of the black hole supermassive events at the center of galaxies and other extreme cosmic events can generate particles with energies impossible to create on Earth. This phenomenon was probably responsible for the 6.3 PeV antineutrino that reached the IceCube in 2016.
“When Glashow was a postdoc at Niels Bohr, he never could have imagined that his unconventional proposal to produce the W boson would be made by an antineutrino from a distant galaxy crashing into the ice of Antarctica,” states in a note. Francesco Halzenprofessor of physics at the University of Wisconsin-Madison, home of IceCube maintenance and operations, and principal investigator of IceCube.
The IceCube telescope became operational in May 2011.
Since IceCube became fully operational in May 2011, the observatory has detected hundreds of high-energy astrophysical neutrinos and has produced a number of significant results in particle astrophysics, including the discovery of a flux of astrophysical neutrinos in 2013 and the first identification of an astrophysical neutrino source in 2018. But the Glashow resonance event is particularly noteworthy for its remarkably high energy; it is only the third event detected by IceCube with an energy greater than 5 PeV.
“This result demonstrates the feasibility of neutrino astronomy and IceCube’s ability to do so, which will play an important role in future multi-messenger astroparticle physics,” he says. Christian Hack, a graduate student at RWTH Aachen while working on this analysis. “We can now detect single neutrino events that are unmistakably of extraterrestrial origin.”
The result also opens a new chapter in neutrino astronomy as it begins to untangle neutrinos from antineutrinos. “Previous measurements have not been sensitive to the difference between neutrinos and antineutrinos, so this result is the first direct measurement of an antineutrino component of astrophysical neutrino flux,” he says. Lu Lu, one of the principal reviewers of this article, who was a postdoc from the University of Chiba in Japan during the review.
Source: Clarin
