Using powerful lasers, scientists have created trillions of positrons — particles of antimatter — opening the way for a better understanding of intense astrophysical processes like gamma-ray bursts and black holes.

Positrons, or "anti-electrons," have the identical mass as an electron but have the opposite charge, and creation of energetic pairs of electrons and positrons are seen in phenomena such as the rapid collapse of stars and the formation of black holes, according to researchers at the Lawrence Livermore National Laboratory in California.

The pairs eventually give up their energy in gamma-ray bursts, the most extreme electromagnetic occurrences witnessed in the universe, but the exact mechanism by which these bursts are formed is as yet not fully understood, notes LLNL physicist Hui Chen.

In their laboratory, Chen and her colleagues created streams of such electron-positron pairs by shining high-energy laser light onto gold foil, resulting in radiation of such high energy that it created the particle pairs as it interacted with the nuclei of gold atoms in the foil.

The capability of producing large numbers of positrons in laboratory settings by using energetic lasers opens avenues to several new approaches to antimatter research, the researchers report in the journal Physical Review Letters.

"The goal of our experiments was to understand how the flux of electron-positron pairs produced scales with laser energy," says Chen, who was the study co-lead author along with former LLNL Fellow Frederico Fiuza, who is now at the SLAC National Accelerator Laboratory at Stanford University.

"Our simulations show that with upcoming laser systems," Fiuza says, "we can study how these energetic pairs of matter-antimatter convert their energy into radiation. Confirming these predictions in an experiment would be extremely exciting."

Such research into antimatter and its behavior could help explain the mystery of why there is more matter than antimatter in the universe today, the researchers point out.

Normal matter and corresponding amounts of antimatter are thought to have existed in roughly equal measure in the extremely early universe, but an "asymmetry" caused the antimatter to decay or be annihilated.

Exactly what process left the observable universe mostly normal matter remains a matter of speculation, the researchers say, with some scientists wondering if there might be other places we cannot yet know of that are almost entirely antimatter.

Scientists like Chen and Fiuza are also curious about what might be possible if antimatter could somehow be harnessed and put to use.

Future work with even more powerful lasers might just begin to answer some of the mysteries, researchers say.

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