Scientists turn lead into gold inside world’s largest particle collider

Deep beneath the French-Swiss border, physicists at the CERN have achieved what medieval alchemists could only dream of: transforming lead into gold.

On July 30, 2025, researchers working on the ALICE experiment at the Large Hadron Collider (LHC) reported that lead ions briefly converted into gold nuclei during high-energy collisions — before decaying almost instantly back into other particles, Earth.com writes.

The transformation lasts only about 10⁻²³ seconds, but it is measurable. And surprisingly, it is not rare.

The 17-mile (27-kilometre) LHC regularly accelerates heavy ions to near the speed of light and smashes them together. But in this case, the gold was produced not in violent head-on crashes, but during so-called ultraperipheral collisions — near-miss encounters where atomic nuclei pass close enough for their powerful electromagnetic fields to interact without direct contact.

“Usually in collider experiments, we make the particles crash into each other to produce lots of debris,” said Daniel Tapia Takaki, professor of physics at the University of Kansas and leader of the group on the ALICE experiment.

Instead of debris, these near-miss events generate intense bursts of high-energy photons. In some cases, the photon barrage knocks three protons out of a lead-208 nucleus. When that happens, the atom briefly becomes gold-205.

The team found that the production cross section for gold nuclei reached 6.8 barns — remarkably close to the 7.67 barns measured for ordinary inelastic lead-lead collisions at the same energy. In practical terms, that means that for roughly every standard heavy-ion collision at the LHC, there is another nearby interaction in which a lead ion quietly transforms into gold and then disintegrates.

Previous runs of ALICE hinted at such clean electromagnetic events, but the detector was optimized for messy central collisions. Tapia Takaki’s group refined the readout system, introduced veto techniques, and developed a two-stage fitting method to isolate proton-loss signals from background noise. The analysis ultimately isolated around two million ultraperipheral events with high precision.

The findings also challenge theoretical models. Measurements of single-proton emission channels differed from predictions by up to 25 percent, suggesting that existing photonuclear models may not fully account for processes such as pre-equilibrium emission and nucleon coalescence.

Beyond its novelty, the research carries practical implications. When lead ions lose protons, they transform into different elements such as thallium or mercury, which bend differently in the LHC’s magnetic fields. These altered ions can strike sensitive components, potentially disrupting superconducting magnets or triggering safety systems.

By mapping proton-loss channels from zero to three protons, the ALICE team has provided crucial data for engineers designing beam shielding and collimation systems — information that will be vital for future accelerator upgrades, including higher-energy LHC operations and the proposed Future Circular Collider.

“Catching a blink of gold,” Tapia Takaki noted, is less about producing treasure and more about ensuring that billion-dollar research facilities operate safely and efficiently.

The team plans to extend the analysis to four- and five-proton emissions as additional Run 3 data become available, pushing further into unexplored territory of high-energy nuclear physics.

For a fleeting instant inside the world’s most powerful particle accelerator, modern science has achieved alchemy — not to create wealth, but to deepen understanding of matter at its most fundamental level.

By Sabina Mammadli