Antimatter particles could cross the galaxy without being destroyed

Experiments at CERN’s particle collider counsel that antihelium particles created by darkish matter in distant house may make it to Earth

By Karmela Padavic-Callaghan

Antimatter from far-off ought to be tough to seek out, because it annihilates when it meets common matter – and the more room it crosses, the extra possibilities there are for these particles to fulfill their finish. But an experiment at a particle collider means that some antimatter particles can journey throughout our galaxy with out getting destroyed.

In house, the antimatter model of the helium atoms’ nuclei – the antihelium nuclei – are thought to kind when cosmic rays collide with free-floating atoms. Theories counsel in addition they come up when particles of darkish matter, a mysterious substance that fills a lot of the universe, annihilate with one another. If antinuclei made in such annihilations had been detected, they might reveal new properties of darkish matter.

Stefan Königstorfer on the Technical University of Munich and his colleagues at the Large Hadron Collider (LHC) wished to see whether or not antinuclei created in house may make it to detectors in Earth’s neighbourhood intact.

First, they measured what number of antihelium nuclei get destroyed after they hit common matter inside a particle collider. Using the ALICE detector at CERN in Switzerland, they analysed collisions of very excessive vitality protons and charged atoms which produced each helium nuclei and antihelium nuclei. Both ought to be produced in equal quantity, so the researchers counted what number of nuclei survived to deduce what number of antinuclei annihilated towards the metal, carbon and different supplies that make up the ALICE detector.

Königstorfer says they used this “disappearance probability” in a pc simulation of antimatter’s journey in direction of Earth from distant house, such because the centre of our galaxy. Simulations of antinuclei being created by darkish matter confirmed that about half of such particles can be detectable close to Earth unscathed, even after traversing 1000’s of trillion kilometres.

The researchers additionally simulated antinuclei being created by cosmic rays, that are theorised to kind at fewer locations within the universe and sometimes with increased energies than these created by darkish matter. They discovered that solely probably the most energetic of them would attain Earth in excessive numbers.

This reveals that any low vitality antihelium nuclei we detect on Earth will seemingly have come from darkish matter, says Jonas Tjemsland on the Norwegian University of Science and Technology.

“This experiment says that if any astrophysical object for any reason produces antihelium, we can detect it near Earth with standard detectors. And the signal to noise ratio will be very high for dark matter,” says Tim Linden at Stockholm University in Sweden.

Understanding how antinuclei work together with interstellar matter is one a part of the puzzle, however the LHC may additionally examine how they kind, says Stefano Profumo on the University of California, Santa Cruz. He says that understanding this higher may assist researchers finetune theories of darkish matter.

Königstorfer and his colleagues are actually planning such experiments. The Alpha Magnetic Spectrometer Experiment on the International Space Station may detect antinuclei already, and one other detector, General AntiParticle Spectrometer, carried by a balloon above Antarctica, will launch quickly.

Journal reference: Nature, DOI: 10.1038/s41567-022-01804-8