Scientists watch particles emerge from empty space for the first time - Earth.com
Researchers have detected particle pairs emerging directly from the vacuum during high-energy proton collisions, providing the clearest evidence yet that mass can arise from empty space.
The finding reframes where much of the weight in ordinary matter comes from, pointing to space itself as an active source rather than a passive backdrop.
Inside the collision
Inside a burst of debris from smashed protons, linked lambda particles appeared with a shared spin pattern that matches quark pairs expected to form in the vacuum.
By tracing that pattern through the collision aftermath, Zhoudunming Tu at Brookhaven National Laboratory showed that the original alignment persisted into the detected particles.
That alignment did not fade immediately, but carried through into short-lived hyperons before those particles decayed and revealed their internal structure.
Such persistence sets a clear boundary for how long vacuum-born order can survive, and it points toward deeper questions about how that order becomes measurable mass.
Spins that survived
Near each other in angle, the lambda and anti-lambda pairs showed an 18 percent relative polarization, with a 4.4 standard-deviation significance.
Such alignment is the signature the team expected if strange quarks and antiquarks emerged from the vacuum already pointing the same way.
Other pairings did not show the same pattern, which made the main signal stand out instead of blending into ordinary collision noise.
That contrast strengthened the case that the linked quark pairs were not random leftovers from the smashup.
Why lambdas mattered
Lambda particles gave the team a useful advantage because their decays preserve clues about the spin carried by the strange quark inside.
When each lambda broke apart in less than a ten-billionth of a second, its daughter particles revealed the parent’s spin direction.
That let the researchers reconstruct whether the two original particles were aligned, even though the quarks themselves never appeared alone.
The method turned a brief decay chain into a readable record of where the particles likely came from.
A vacuum with structure
Modern physics no longer treats a vacuum as blank emptiness, because energy fields inside it constantly flicker and briefly create particle pairs.
In quantum chromodynamics (QCD), the theory of the strong force, quarks are bound so tightly that free ones never last on their own.
Under enough stress, however, those fleeting pairs can be promoted into real ingredients of larger particles after a high-energy collision.
That is why this result matters beyond one detector, because it treats the vacuum as an active source of matter.
Where the visible mass comes from
The Higgs field remains essential because it gives elementary particles their baseline masses, a picture confirmed by CERN in 2012 through the Higgs boson.
Protons and neutrons, though, weigh far more than the small masses of their individual quarks would suggest.
Most visible mass therefore seems to come from the energy of the strong interaction and the vacuum conditions surrounding confined quarks.
This new signal does not solve that problem outright, but it gives physicists a fresh experimental handle on it.
When order breaks down
Distance weakened the effect, because widely separated particle pairs lost the shared alignment seen in close pairs.
Researchers describe that loss as decoherence, a fading of quantum order as interactions scramble an initially linked system.
Instead of staying tightly coordinated, the spins looked ordinary once the pair separation grew large enough in the detector.
That drop matters because it suggests the signal was real at birth rather than created later by the measurement.
What the signal ruled out
Competing explanations had to be checked, since particle collisions can mimic meaningful patterns when many processes pile together.
The team compared its data with baseline cases and found no matching spin correlation in kaon pairs or in standard event simulations.
It also examined other possible sources, including gluon splitting and later interactions among produced particles, and reported them as negligible.
Those checks do not end the debate, but they narrow the room for simpler explanations.
A new experimental handle
STAR was built to track huge showers of debris from energetic collisions, and the detector itself is house-sized and weighs about 1,200 tons on the Brookhaven site in New York STAR.
RHIC also occupies a special place in physics because it has been the world’s only collider able to smash polarized proton beams together for spin studies at high energy RHIC.
That combination let the collaboration study not just what particles were made, but how their internal spin information traveled through confinement.
The result opens a route toward testing how vacuum structure, spin, and mass emergence fit into the same story.
Limitations and future research
Not everyone sees the case as closed, because reconstructing complicated collisions still leaves room for hidden backgrounds and missed effects.
Tu framed the promise plainly when he said the measurement opens a new way to examine the vacuum directly.
Future runs could test higher momenta, different collision settings, and hotter environments where the vacuum itself may behave differently.
Those follow-up studies could show whether this observed pathway is a special case or part of a broader rule.
Empty space now looks less like a silent backdrop and more like an active participant in building the mass and structure of visible matter.
Physicists still do not know the full mechanism, but they finally have a signal that follows vacuum-born order all the way into detectable particles.
The study is published in the journal Nature.
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