CERN Physicists Generate Early Universe Matter Using Surprisingly Small Atomic Nuclei

Researchers at CERN have successfully reproduced a state of matter from the Universe's infancy by colliding much smaller atomic nuclei than previously thought possible. This groundbreaking experiment formed quark-gluon plasma and demonstrated that the particles produced help reveal the shapes of the nuclei involved.

Undertaken by scientists from the Niels Bohr Institute at the University of Copenhagen alongside the international ALICE collaboration, the study overturns earlier notions regarding the minimum nuclear size needed to replicate primordial matter. By smashing oxygen-16 and neon-20 nuclei at speeds approaching that of light, the team recreated conditions akin to those shortly after the Big Bang.

Within the first microseconds after the birth of the Universe, temperatures soared so high that protons and neutrons had not yet formed. Instead, their subcomponents, quarks and gluons, existed in an ultra-hot phase called quark-gluon plasma.

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The University of Copenhagen notes that findings published in Physical Review Letters confirm that smaller nuclei can also generate this rare matter state. This discovery opens new pathways for exploring the Universe’s earliest moments and nuclear structures.

Primordial Matter Emerges from Smaller-Scale Collisions

For many years, physicists relied on the collision of large nuclei, like lead, to investigate quark-gluon plasma. Those tests demonstrated that extreme energies can momentarily revive the early Universe’s matter. This recent achievement reduces the expected scale, as quark-gluon plasma emerged from interactions between the much smaller oxygen-16 and neon-20 nuclei.

The plasma generated exists for only a fleeting instant before expanding and transforming into particles. While direct observation is impossible, the resulting particles carry clues about the brief plasma phase.

“We have pushed the boundary for how small the atomic nuclei can be while still recreating this primordial matter,” said You Zhou, associate professor and leader of the experiment, according to the University of Copenhagen.

This breakthrough enhances physicists’ comprehension of the energy conditions needed to form quark-gluon plasma and sparks fresh inquiries into the smallest viable collision systems capable of producing it.

Particle Traces Reveal Original Nuclear Shapes

An unexpected discovery from the experiment is that the emitted particles retain imprints of the nuclei’s original geometry. Distinct nuclear collisions produced differing particle flow patterns: the two oxygen-16 nuclei showed signals connected to a more spherical shape, while neon-20 interactions reflected its elongated, bowling-pin-like form.

“It is a bit like shining light on an object and seeing its shadow,” explained Emil Gorm Dahlbæk Nielsen from the Niels Bohr Institute, a co-author of the study. The movement of the particles acts as a trace of the shape that existed before the collision.

This innovative technique complements traditional nuclear physics methods. Instead of focusing solely on lower-energy nuclear rotations and vibrations, researchers can now reconstruct nuclear shapes and properties through patterns generated in high-energy collisions.

Links Between Nuclear Physics and Cosmic Origins

The configuration of an atomic nucleus reveals how protons and neutrons are spatially arranged, providing insights into the strong nuclear force, a fundamental interaction that directs matter's behavior.

With over seven decades dedicated to nuclear structure research—including notable contributions from the Niels Bohr Institute—this novel high-energy collision approach offers a fresh method to unravel nuclei characteristics previously difficult to probe. According to the original paper, upcoming experiments plan to explore even lighter nuclei like helium-4 to identify the smallest systems capable of producing quark-gluon plasma.

This work bridges two critical scientific questions once seen as unrelated: the internal organization of the tiniest building blocks of matter and the evolution of the Universe’s earliest material. By generating minuscule bursts of primordial matter within the Large Hadron Collider, researchers gain invaluable knowledge on both atomic structures and the Universe's origins.

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