Antimatter particles might cross the galaxy with out being destroyed

Experiments at CERN’s particle collider recommend that antihelium particles created by darkish matter in distant area might make it to Earth

By Karmela Padavic-Callaghan

Antimatter from distant must be difficult to seek out. It annihilates when it meets common matter – and the more room it crosses, the extra possibilities there are for these particles to satisfy their finish. However an experiment at a particle collider means that some antimatter particles can journey throughout our galaxy with out getting destroyed.

In area, the antimatter model of helium atoms’ nuclei – the antihelium nuclei – are thought to type when cosmic rays collide with free-floating atoms. Theories recommend additionally they come up when particles of darkish matter, a mysterious substance that fills many 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 College of Munich in Germany and his colleagues on the Massive Hadron Collider (LHC) needed to see whether or not antinuclei created in area might make it to detectors in Earth’s neighbourhood intact.

First, they measured what number of antihelium nuclei get destroyed once they hit common matter inside a particle collider. Utilizing the ALICE detector on the CERN particle physics laboratory in Switzerland, they analysed collisions of very high-energy protons and charged atoms, which produced each helium nuclei and antihelium nuclei. Each must 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 (A Massive Ion Collider Experiment) detector.

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

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

This reveals that any low-energy antihelium nuclei we detect on Earth will probably have come from darkish matter, says Jonas Tjemsland on the Norwegian College of Science and Expertise.

“This experiment says that if any astrophysical object for any motive produces antihelium, we are able to detect it close to Earth with normal detectors. And the signal-to-noise ratio will probably be very excessive for darkish matter,” says Tim Linden at Stockholm College in Sweden.

Understanding how antinuclei work together with interstellar matter is one a part of the puzzle, however the LHC might additionally examine how they type, says Stefano Profumo on the College of California, Santa Cruz. He says that understanding this higher might assist researchers fine-tune theories of darkish matter.

Königstorfer and his colleagues are actually planning such experiments. The Alpha Magnetic Spectrometer experiment on the Worldwide Area Station might detect antinuclei already, and one other detector, Basic AntiParticle Spectrometer, carried by a balloon above Antarctica, will launch quickly.

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