Today's KNOWLEDGE Share : CERN Scientists turn lead into gold

Today's KNOWLEDGE Share

CERN Physicists Observe Conversion of Lead into Gold

Near-miss collisions between high-energy lead nuclei at CERN’s Large Hadron Collider generate intense electromagnetic fields that can knock out protons and transform lead into fleeting quantities of gold nuclei.

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 gray, relatively abundant lead is of a similar density to gold, which has long been coveted for its beautiful color 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, physicists with the ALICE Collaboration at CERN’s Large Hadron Collider (LHC) have 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, the very high speed at which lead nuclei travel in the LHC causes the electromagnetic field lines to be squashed into a thin pancake, transverse to the direction of motion, producing a short-lived pulse of photons.

Often, this triggers a process called electromagnetic dissociation, whereby a photon interacting with a nucleus can excite oscillations of its internal structure, resulting in the ejection of small numbers of neutrons and protons.

To create gold (a nucleus containing 79 protons), three protons must be removed from a lead nucleus in the LHC beams.

“It is impressive to see that our detectors can handle head-on collisions producing thousands of particles, while also being sensitive to collisions where only a few particles are produced at a time, enabling the study of electromagnetic ‘nuclear transmutation’ processes,” said ALICE spokesperson Dr. Marco Van Leeuwen, a physicist at NIKHEF.

The new results appear in the journal Physical Review C

source: SCI NEWS