ALICE detects the conversion of lead into gold at the LHC

Summary

Near-miss collisions between high-energy lead nuclei at the LHC generate intense electromagnetic fields that can knock out protons and transform lead into fleeting quantities of gold nuclei In a paper published in Physical Review Journals, the ALICE collaboration reports measurements that quantify the transmutation of lead into gold in CERN’s Large Hadron Collider (LHC). Transforming the base metal lead into the precious metal gold was a dream of medieval alchemists. This long-standing quest, known as chrysopoeia, may have been motivated by the observation that dull grey, relatively abundant lead is of a similar density to gold, which has long been coveted for its beautiful colour and rarity. It was only much later that it became clear that lead and gold are distinct chemical elements and that chemical methods are powerless to transmute one into the other. With the dawn of nuclear physics in the 20th century, it was discovered that heavy elements could transform into others, either naturally, by radioactive decay, or in the laboratory, under a bombardment of neutrons or protons. Though gold has been artificially produced in this way before, the ALICE collaboration has now measured the transmutation of lead into gold by a new mechanism involving near-miss collisions between lead nuclei at the LHC. Extremely high-energy collisions between lead nuclei at the LHC can create quark–gluon plasma, a hot and dense state of matter that is thought to have filled the universe around a millionth of a second after the Big Bang, giving rise to the matter we now know. However, in the far more frequent interactions where the nuclei just miss each other without “touching”, the intense electromagnetic fields surrounding them can induce photon–photon and photon–nucleus interactions that open further avenues of exploration. The electromagnetic field emanating from a lead nucleus is particularly strong because the nucleus contains 82 protons, each carrying one elementary charge. Moreover...