Scientists Confirm Particles Emerge from Vacuum in Groundbreaking Experiment

Scientists at the Relativistic Heavy Ion Collider (RHIC) have made a significant breakthrough by observing particles emerging directly from empty space, a phenomenon that confirms a long-standing prediction of quantum chromodynamics (QCD). This discovery, reported by the STAR collaboration at Brookhaven National Laboratory in New York, involved high-energy proton collisions within the lab's Solenoidal Tracker detector. Researchers detected rare quark-antiquark pairs that originated from the vacuum itself, rather than from the colliding protons, providing compelling evidence that matter can materialize from what classical physics considers empty space.

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Quantum chromodynamics, the established theory governing the strong force that binds quarks within protons and neutrons, posits that a perfect vacuum is not truly empty. Instead, it is filled with constant fluctuations known as virtual particles, including ephemeral quark-antiquark pairs. Under normal conditions, these pairs appear and vanish almost instantaneously. However, when sufficient energy is supplied, QCD predicts that these virtual particles can become real, measurable particles.

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In the STAR experiment, proton collisions generated a cascade of particles. Since free quarks cannot exist independently, the quarks produced from the vacuum immediately combined into composite particles called hyperons. The STAR team identified crucial evidence in the form of the particles' quantum property of spin. The quarks and antiquarks born from the vacuum exhibited correlated spins—a shared alignment established at their creation. This correlation persisted as the quarks formed hyperons and remained even after the hyperons decayed in less than a tenth of a billionth of a second. The detection of these spin-aligned hyperons allowed researchers to trace the quarks' origin back to the vacuum, rather than to the original collision debris.

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This finding has significant implications for one of the central puzzles in physics: the origin of particle mass. Quantum chromodynamics suggests that quarks acquire most of their mass through interactions with the vacuum, yet the precise mechanism has remained elusive. The new observation provides a direct experimental basis for studying these vacuum interactions, although researchers caution that the results are not yet definitive and further investigations are necessary to rule out other potential factors that may have influenced the signal.

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Future runs at the Relativistic Heavy Ion Collider, along with complementary experiments at other facilities, will aim to refine these findings. The STAR collaboration's work not only marks the first direct observation of vacuum-derived matter but also sets the stage for further tests of quantum chromodynamics at the energy frontier. This research opens new experimental avenues to explore the properties of vacuum and the mass-generation process predicted by QCD.

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“This is the first time we’ve seen the whole process,” — Zhoudunming You, STAR collaboration member.

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