In a scientific milestone that challenges the traditional understanding of emptiness, researchers at the Relativistic Heavy Ion Collider at Brookhaven National Laboratory in New York have observed particles emerging from a vacuum for the first time. This phenomenon, predicted by the theory of quantum chromodynamics (QCD), offers a glimpse into how particles acquire mass from nothing.
According to QCD, a perfect vacuum is not truly empty but filled with ephemeral disturbances in the underlying energy of space, known as virtual particles. Among these, quark-antiquark pairs are prominent, appearing and disappearing almost instantaneously. However, when sufficient energy is injected into the vacuum, the theory predicts that these transient entities can be promoted to real, detectable particles with measurable mass.
The experiment, conducted by the STAR collaboration, involved colliding high-energy protons in a vacuum, resulting in a spray of particles. Some of these particles are believed to be quark-antiquark pairs extracted directly from the vacuum. Quarks, however, never exist in isolation, immediately combining into composite particles. The crucial discovery was that even after forming hyperons—larger particles that decay in less than a tenth of a billionth of a second—the spin correlation inherited from the vacuum was still present.
This discovery was celebrated by Zhoudunming Tu, a member of the STAR collaboration, who highlighted the importance of visualizing the complete process for the first time. Daniel Boer from the University of Groningen, who was not involved in the study, emphasized the unresolved mysteries about quarks, such as why they cannot exist alone, underscoring the experiment’s relevance. Alessandro Bacchetta from the University of Pavia cautioned that the result is not yet definitive, due to the complexity of reconstructing particle collision events, indicating the need to exhaustively rule out other possibilities that could generate the same signal.
The research, which paves the way for studying the properties of the vacuum and how particles acquire mass, was reported by New Scientist. It is expected that future investigations may elucidate how quarks interact with the vacuum to gain mass, a puzzle that remains obscure in current physics.
Original published at O Cafezinho.