(CN) — Deep in the heart of Long Island at the U.S. Department of Energy's Brookhaven National Laboratory in New York, research scientists studying the conditions that formed the universe discovered of a new kind of antimatter antinucleus.
Scientists detail in their study published Wednesday in the journal Nature how members of the Relativistic Heavy Ion Collider's STAR Collaboration discovered the heaviest antimatter nucleus ever detected, antihyperhydrogen-4.
The RHIC, a kind of particle accelerator termed an “atom smasher,” collides the atomic nuclei of gold atoms together close to the speed of light, then heats the matter to more than a billion times the temperature of the sun, which melts the boundaries of the ions protons and neutrons.
The energy of the collision deposited in a stew of quarks and gluons, the elementary particles of all matter, generates thousands of new particles. Studying the results of those collisions allows physicists to investigate the basic building blocks of matter and how they acted 15 to 20 billion years ago when the universe began.
“Why our universe is dominated by matter is still a question, and we don’t know the full answer,” Junlin Wu, a graduate student at the Joint Department for Nuclear Physics, Lanzhou University and Institute of Modern Physics, China said in a statement.
Another vexing question for scientists is the imbalance of matter and antimatter in the universe.
Antimatter is the counterpart to matter. Antiatoms have almost the exact same characteristics and behaviors as matter atoms but with the opposite charge.
For example, atoms contain electrons which have a negative electrical charge. Antimatter atoms contain positrons, which behave the same way as electrons but have a positive electrical charge.
Antimatter and matter atoms annihilate upon contact, creating a flash of energy, which makes antimatter difficult to create and work with.
The Big Bang should have created a similar amount of matter and antimatter in the universe, but there is a comparatively small amount of antimatter when compared to matter, which is basically everything we see in the universe.
Researchers say comparing characteristics of matter and antimatter particles generated in these particle collisions can offer clues to why that asymmetry happened.
“To study the matter-antimatter asymmetry, the first step is to discover new antimatter particles,” said STAR Collaboration physicist Hao Qiu, in a statement. “That’s the basic logic behind this study.”
STAR researchers had previously observed antimatter nuclei created in RHIC collisions, like a particle dubbed the antihypertriton and the antimatter equivalent of a helium nucleus called antihelium-4.
The scientists then had to retrace the trajectories of the antihelium-4 and positively charged particles called pi+ particles, to see if they emerged from a single point. To do that, they had to sift through billions of collision events to find the particles.
“The key was to find the ones where the two particle tracks have a crossing point, or decay vertex, with particular characteristics,” said Brookhaven Lab physicist Lijuan Ruan, one of two co-spokespersons for the STAR Collaboration.
The researchers then compared the lifetime of the antihyperhydrogen-4 with its twin, hyperhydrogen-4 and made comparisons between other matter-antimatter pairs, like the antihypertriton and the hypertriton.
The results were a test of a strong form of symmetry and a confirmation that the rules of physics still operated as we've assumed.
“If we were to see a violation of [this particular] symmetry, basically we’d have to throw a lot of what we know about physics out the window,” said Emilie Duckworth, a doctoral student at Kent State University who maintained the computer code used to sift through the collision events.
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