By Becca Lewis | Published
Antimatter is all around us, but it’s less well understood than matter. Antimatter is the opposite of matter in some ways, it carries a negative electric charge, and scientists recently discovered the heaviest antimatter atomic nuclei ever detected. Antimatter has proven to be a difficult type of particle to study because it’s much rarer than matter, even though it likely originated in equal amounts about 14 billion years ago.
Scientists still don’t understand why antimatter is so much less abundant than matter in our universe, so the quest for its origin is a quest for the beginning of existence as we understand it.
The heavy antimatter nucleus was discovered by researchers at the Relativistic Heavy Ion Collider in Upton, New York, by analyzing the trail left by six billion atomic collisions. The STAR Collaboration team, operating a solenoid tracker, discovered the new particle, which they have named antihyperhydrogen-4. This significant discovery surpasses the previous record holder for the heaviest antimatter nucleus, antihelium-4.
While antimatter particles are intentionally created during “atomic collision” experiments in colliders, the combination of elements required to create this newly discovered heavy antimatter nucleus is purely by chance.
To find the heaviest antimatter nucleus ever detected, STAR scientists tracked the orbits of antihelium-4 and another particle called a pion, recording their tiny trails through the masses of matter and antimatter particles produced by the collider. The team was looking for a few cases out of billions where the orbits of pion and antihelium-4 particles intersected, suggesting they might have occurred when the same nucleus decayed. And the team speculated that about 22 of these events could have come from a larger particle, antihyperhydrogen-4.
Of the 22 cases in which antihelium-4 and pion particles could be the result of the decay of single atomic nuclei, 16 were verified to be associated with the degradation of antihyperhydrogen-4 nuclei. The other six were determined to be “noise,” i.e., not arising from a single antimatter nucleus. Based on these calculations, the researchers concluded that they had discovered the heaviest new antimatter particle to date.
Scientists working on the STAR project are using newly discovered heavy antimatter nuclei to investigate the interactions of matter and antimatter.
The study of the symmetry between matter and antimatter is only possible by first observing antimatter particles. Scientists still do not understand why antimatter is so much less abundant than matter in the universe. The search for the origin of antimatter is the search for the beginning of existence as we understand it. Unravelling the mysteries of the universe is heavily tied to unravelling the mystery of heavy antimatter and how it interacts with matter.
Matter and antimatter are similar in most ways that our current understanding of physics can measure: they have the same mass, they last the same amount of time before they decay, they interact with charged particles in the same way, and so apart from matter being positively charged and antimatter being negatively charged, they are similar in every observable way.
Scientists working on the STAR project are using newly discovered heavy antimatter nuclei to investigate the interactions of matter and antimatter.
Antimatter has been difficult to observe until now because it is unstable, especially since the particles are submicroscopic. But the Relativistic Heavy Ion Collider is the perfect place to look for antimatter particles, because scientists there deliberately create them.
The STAR Collaboration team, operating the Solenoid Tracker, discovered this new particle and named it Antihyperhydrogen-4.
sauce: Brookhaven National Laboratory
