Credit: Brookhaven National Laboratory
For the first time, scientists have measured the forces that make certain antimatter particles stick together.
The findings, published in Nature, may yield clues to what led to the scarcity of antimatter in the cosmos today.
"Antimatter is extremely rare. It's a huge mystery!" said physicist Aihong Tang, from the Brookhaven National Laboratory, who was involved in the study.
"Although this puzzle has been known for decades and little clues have emerged, it remains one of the big challenges of science. Anything we learn about the nature of antimatter can potentially contribute to solving this puzzle."
Video: Physicists measure force that makes antimatter stick together
Tang and colleagues conducted an experiment using the Relativistic Heavy Ion Collider (RHIC) at Brookhaven. The giant particle accelerator smashed atoms of pure gold, producing antimatter particles with the raw energy of the collisions.
The researchers then looked at the antimatter counterpart of proton. Proton is the positively charged particle at the center of a matter's atom. Its antimatter counterpart, called antiproton, is negatively charged.
The scientists found that the force between antiproton pairs is attractive, just like the strong nuclear force that holds ordinary atoms together. Considering they'd already discovered bound states of antiprotons and antineutrons-those antimatter nuclei-this wasn't all that surprising. When the antiprotons are close together, the strong force interaction overcomes the tendency of the like (negatively) charged particles to repel one another in the same way it allows positively charged protons to bind to one another within the nuclei of ordinary atoms.
In fact, the measurements show no difference between matter and antimatter in the way the strong force behaves. That is, within the accuracy of these measurements, matter and antimatter appear to be perfectly symmetric. That means, at least with the precision the scientists were able to achieve, there doesn't appear to be some asymmetric quirk of the strong force that can account for the continuing existence of matter in the universe and the scarcity of antimatter today.
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