Physicists have created the heaviest clumps of antimatter particles ever seen. This strange stuff, known as antihyperhydrogen-4, could help solve some of the most puzzling mysteries of physics.
Antimatter is basically ordinary matter with the opposite charge. That's all. It doesn't sound very exciting when put that way, but there are big implications to this simple difference: essentially, when matter and antimatter come together, they annihilate each other in a burst of energy. If we can harness this, we could build the most efficient spacecraft engines or the most destructive weapons ever. For as long as we know humanity, we've been putting our money on the latter.
Anyway, every particle has an antiparticle, and these should be able to come together to form larger antiatoms of familiar elements – antihydrogen and antihelium have been produced, but theoretically there should be a whole anti-periodic table.
Now scientists have created the heaviest antimatter nucleus yet, a substance known as antihyperhydrogen-4. It consists of one antiproton, two antineutrons, and one antihyperon. While protons and neutrons are well-known, hyperons are less well-known, but they are essentially a slightly heavier version of a neutron.
These antinuclei were produced at the Relativistic Heavy Ion Collider (RHIC), a particle accelerator that recreates the conditions of the early universe. Here, heavy elements are collided to produce showers of new particles, including some antimatter particles. In extremely rare cases, some of these antimatter particles will collide to form more complex antinuclei. In fact, of the billions of particles produced in these collisions, only 16 antihyperhydrogen-4 nuclei have been confidently detected.
“It's pure coincidence that these four component particles from the RHIC collisions happened to be close enough together that they merged to form this antihypernucleus,” said Lijuan Ruan, co-spokesperson for the project.
Joe Rubino and Jen Abramowitz/Brookhaven National Laboratory
Detecting them isn’t easy — these antihyperhydrogen-4 nuclei decay in about a tenth of a nanosecond. Instead, instruments detect the particles they decay into, tracing their paths back to see if they travel a certain distance after the original heavy atoms collided, briefly “sticking together” in the nucleus.
From their detections, the team were able to compare the lifetime of antihyperhydrogen-4 with the lifetime of hyperhydrogen-4 and found that they appeared to be identical. This was expected, since matter and antimatter of the same elements should only differ in their charges – but there is also the possibility that there are other differences that point to physics beyond the Standard Model.
Better understanding antimatter could help answer one of physics’ deepest questions: why are we here? Our best models suggest that matter and antimatter should have been created in equal amounts in the Big Bang, but if that’s the case, continual annihilation events should have left the universe essentially empty by now.
Since this clearly didn't happen, there must have been a slight imbalance that created more matter than antimatter, and studying the differences between the two could help us figure out what happened. The next steps in the investigation are to check the differences in the masses of these particles and antiparticles.
The study was published in the journal Nature.
Sources: Brookhaven National Laboratory, The Conversation