Scientists at CERN’s ALICE detector are recreating Big Bang-like conditions, aiming to uncover why matter Particle triumphed over antimatter in shaping the universe as we know it.
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Breakthrough: Large Hadron Collider Unveils Heaviest Antimatter Particle Ever Detected
The world’s largest scientific experiment has done it again, uncovering tantalizing evidence of the heaviest antimatter particle ever detected.
Using the Large Hadron Collider (LHC)—the most powerful particle accelerator ever built—scientists have glimpsed conditions that existed less than a second after the universe was born. This groundbreaking discovery involves the antimatter counterpart of hyperhelium-4, a massive matter particle. It could help unravel the enduring mystery of why the universe is dominated by matter, even though matter and antimatter were produced in equal amounts at the dawn of time.
This imbalance, known as “matter-antimatter asymmetry,” is a cosmic puzzle. When matter and antimatter meet, they annihilate each other, releasing energy. Without an early imbalance, the universe might have been a desolate void rather than the vibrant cosmos we know today.
The LHC, located in a 17-mile (27-kilometer) loop beneath the Alps near Geneva, Switzerland, has a history of redefining our understanding of the universe. It is most famous for discovering the Higgs Boson, the particle linked to the Higgs Field, which gives other particles their mass.
At the heart of the LHC’s operations is the creation of “quark-gluon plasma,” a state of matter that mirrors the “primordial soup” filling the universe just a millionth of a second after the Big Bang. This plasma gives rise to exotic “hypernuclei” and their antimatter equivalents, providing scientists a rare window into the universe’s earliest moments.
With this new discovery, the LHC continues to push the boundaries of what we know, bringing us closer to answering one of the most profound questions of existence: why does matter prevail over antimatter?
An image of the ALICE detector taken during LHC upgrades in 2019 (Image credit: Robert Lea)
ALICE Through the Looking Glass: Unlocking the Secrets of Hypernuclei
Hypernuclei, extraordinary relatives of ordinary atomic nuclei, offer a fascinating glimpse into the building blocks of the universe. Like traditional nuclei, they contain protons and neutrons, but they also feature hyperons—exotic, unstable particles made of quarks. While protons and neutrons consist of up and down quarks, hyperons include at least one “strange quark,” adding an intriguing twist to their structure.
First discovered in cosmic ray showers around seven decades ago, hypernuclei are incredibly rare and challenging to study in the laboratory. Their elusive nature has kept them shrouded in mystery, making their recent discovery at CERN’s ALICE detector a monumental breakthrough. For the first time, scientists have found evidence of the antimatter counterpart of hyperhelium-4, marking a significant leap forward in particle physics.
The ALICE Collaboration’s Unique Approach
Unlike most Large Hadron Collider (LHC) experiments, which involve high-speed proton collisions, ALICE focuses on creating quark-gluon plasma—a primordial state of matter from the universe’s earliest moments. To achieve this, ALICE slams together much heavier particles, such as lead nuclei, at near-light speeds. These heavy-ion collisions are ideal for producing hypernuclei, enabling scientists to explore the properties of these rare particles.
Despite these advancements, earlier experiments had only detected the lightest hypernucleus, hypertriton, and its antimatter counterpart, antihypertriton. This changed dramatically in early 2024 when the Relativistic Heavy Ion Collider (RHIC) in New York detected antihyperhydrogen-4, a complex particle composed of an antiproton, two antineutrons, and an antilambda—a quark-containing particle.
ALICE’s Breakthrough Discovery
Building on this momentum, ALICE achieved a landmark result: the detection of antihyperhelium-4, a heavier anti-hypernucleus. This exotic antimatter particle consists of two antiprotons, an antineutron, and an antilambda. By achieving this milestone, ALICE has provided an unprecedented opportunity to study the properties of hypernuclei and their antimatter counterparts, shedding light on the fundamental forces that governed the universe’s formation.
Unlocking the Mysteries of the Early Universe
These discoveries are far more than technical achievements—they are crucial steps in solving one of the universe’s deepest puzzles: matter-antimatter asymmetry. Understanding the behavior of hypernuclei and their antimatter equivalents in quark-gluon plasma could reveal why matter came to dominate over antimatter, enabling the cosmos to exist as we know it.
Through innovative techniques and collaboration, ALICE continues to push the boundaries of particle physics, offering new insights into the nature of matter and the origins of the universe. The journey into the subatomic world is far from over, but with each discovery, we get closer to unraveling the mysteries of existence itself.
An illustration of antimatter particles entering the ALICE detector at the Large Hadron Collider. (Image credit: ORIGINS Cluster/S. Kwauka)
The lead-lead collision and the ALICE data that yielded the detection of the heaviest antimatter hypernucleus yet at the LHC actually date back to 2018.
The signature of antihyperhelium-4 was revealed by its decay into other particles and the detection of these particles.
ALICE scientists teased the signature of antihyperhelium-4 out of the data using a machine-learning technique that can outperform the collaboration’s usual search techniques.
In addition to spotting evidence of antihyperhelium-4 and antihyperhydrogen-4, the ALICE team was also able to determine their masses, which were in good agreement with current particle physics theories.
The scientists were also able to determine the amounts of these particles produced in lead-lead collisions.
They found these numbers consistent with the ALICE data, which indicates that antimatter and matter are produced in equal amounts from quark-gluon plasma produced at the energy levels the LHC is capable of reaching.
The reason for the universe’s matter/antimatter imbalance remains unknown, but antihyperhelium-4 and antihyperhydrogen-4 could provide important clues in this mystery.