From Alchemy to Atomic Precision: CERN’s ALICE Experiment Detects Gold from Lead

In a remarkable intersection of ancient dreams and modern science, researchers at CERN have observed the transmutation of lead into gold — not via alchemy, but through high-energy electromagnetic interactions in the world’s most powerful particle accelerator.

A Modern-Day Chrysopoeia
Centuries ago, alchemists sought to convert base metals like lead into gold. While chemically impossible, today’s nuclear physics reveals that atomic elements can indeed transform under specific conditions. A new study published by the ALICE collaboration in Physical Review Journals details how near-miss collisions of lead nuclei at the Large Hadron Collider (LHC) have produced fleeting quantities of gold nuclei.

This process occurs during what are known as ultra-peripheral collisions. Rather than colliding directly, lead nuclei pass close to each other at velocities nearing the speed of light (99.999993% of c), generating ultra-intense electromagnetic fields. These interactions release photons that, upon striking a nucleus, can cause it to shed protons and neutrons. Specifically, if a lead nucleus (82 protons) loses three protons and at least one neutron, it temporarily forms a gold nucleus (79 protons).

Detecting Atomic Alchemy
The ALICE detector’s Zero Degree Calorimeters (ZDCs) played a crucial role in identifying these rare events. They measured the number of ejected protons and neutrons, correlating each pattern with the formation of elements such as thallium, mercury, and gold. Though gold production was the least frequent, the team determined that during LHC Run 2 (2015–2018), around 86 billion gold nuclei were generated — equivalent to only 29 picograms in total mass.

The process is transient: the gold nuclei exist only for a fraction of a second before disintegrating into subatomic particles upon colliding with the LHC’s beam infrastructure. Theoretically impressive, the practical outcome remains negligible in terms of material yield.

Implications for Design and Materials Innovation
While this experiment does not immediately translate into usable quantities of material, it demonstrates the precision and control achievable in nuclear-level transformations. Furthermore, the insights gained contribute to the improvement of theoretical models of electromagnetic dissociation, which influence how particle beams are managed and optimized. These models may one day assist in designing more efficient particle-based processes for material modification or even atomic-scale manufacturing.

A Cautionary Conclusion
Despite fulfilling the alchemists’ dream in principle, this feat remains firmly in the realm of experimental physics. The production rate — 89,000 gold nuclei per second — sounds impressive until one realises that billions are needed just to see a speck of gold. Still, such discoveries reflect the incredible strides being made in scientific understanding and open imaginative possibilities for the future of materials science.

Source: CERN
Photo: Pixabay