• Physicists at the Large Hadron Collider (LHC) in CERN have turned lead into gold for a tiny fraction of a second.

• 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.

How lead turned into gold?

• 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 (corresponding to 99.999993 per cent of the speed of light) 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.

• The ALICE team used the detector’s zero degree calorimeters (ZDC) to count the number of photon–nucleus interactions that resulted in the emission of zero, one, two and three protons accompanied by at least one neutron, which are associated with the production of lead, thallium, mercury and gold, respectively. 

• While less frequent than the creation of thallium or mercury, the results showed that the LHC produced gold at a maximum rate of about 89,000 nuclei per second from lead–lead collisions at the ALICE collision point. 

• Gold nuclei emerged from the collision with very high energy and hit the LHC beam pipe or collimators at various points downstream, where they immediately fragment into single protons, neutrons and other particles. 

• The gold existed for just a tiny fraction of a second.

What is CERN?

• CERN is the world’s leading laboratory for particle physics. 

• Its headquarters is situated in Geneva. 

• The CERN convention was signed in 1953 by 12 founding countries and entered into force on September 29, 1954.

• Today CERN has 24 Member States: Austria, Belgium, Bulgaria, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Israel, Italy, Netherlands, Norway, Poland, Portugal, Romania, Serbia, Slovak Republic, Spain, Sweden, Switzerland and United Kingdom.

• Cyprus and Slovenia are Associate Member States in the pre-stage to Membership. 

• Brazil, Croatia, India, Latvia, Lithuania, Pakistan, Türkiye and Ukraine are Associate Member States.

• Japan and the United States of America hold Observer status.

• Over 600 institutes and universities around the world use CERN’s facilities. 

• Funding agencies from both Member and Non-Member States are responsible for the financing, construction and operation of the experiments on which they collaborate. 

• CERN spends much of its budget on building machines such as the Large Hadron Collider and it only partially contributes to the cost of the experiments.

• Since CERN began in 1954, it has made many significant breakthroughs, both in particle physics (such as our early discovery of neutral currents) and technologies that have helped improve our day-to-day lives (including the World Wide Web). Tim Berners-Lee, a British scientist, invented the World Wide Web (WWW) in 1989, while working at CERN.

What is Large Hadron Collider (LHC)?

• The Large Hadron Collider (LHC) is the most powerful particle accelerator ever built. 

• The accelerator sits in a tunnel 100 metres underground at CERN on the Franco-Swiss border near Geneva, Switzerland.

• It first started up on September 10, 2008.

• It consists of a 27-kilometre ring of superconducting magnets with a number of accelerating structures that boost the energy of the particles along the way.

• Inside the accelerator, two high-energy particle beams travel at close to the speed of light before they are made to collide at four locations around its ring.

• The beams travel in opposite directions in separate beam pipes — two tubes kept at ultrahigh vacuum. They are guided around the accelerator ring by a strong magnetic field maintained by superconducting electromagnets. 

• The detectors gather clues about the particles – including their speed, mass and charge – from which physicists can work out a particle’s identity.

Why is it called the Large Hadron Collider?

• “Large” refers to its size, approximately 27km in circumference.

• “Hadron” because it accelerates protons or ions, which belong to the group of particles called hadrons.

• “Collider” because the particles form two beams travelling in opposite directions, which are made to collide at four points around the machine.

Discovery of the Higgs boson

• On July 4, 2012, the ATLAS and CMS collaborations at the Large Hadron Collider (LHC) announced the discovery of a new particle with features consistent with those of the Higgs boson predicted by the Standard Model of particle physics. 

• Two research groups of some 3,000 scientists each, ATLAS and CMS, managed to extract the Higgs particle from billions of particle collisions in the LHC.

• The Standard Model of particle physics describes how the world is constructed. According to the Standard Model, everything, from flowers and people to stars and planets, consists of just a few building blocks: matter particles. These particles are governed by forces mediated by force particles that make sure everything works as it should.

• The entire Standard Model also rests on the existence of a special kind of particle: the Higgs particle. This particle originates from an invisible field that fills up all space. Even when the universe seems empty this field is there. Without it, we would not exist, because it is from contact with the feld that particles acquire mass. The theory proposed by Francois Englert and Peter Higgs describes this process.

• The discovery was a landmark in the history of science and captured the world’s attention.

• One year later, it won Francois Englert and Peter Higgs the Nobel Prize in Physics for their prediction made decades earlier, together with the late Robert Brout, of a new fundamental field, known as the Higgs field, that pervades the universe, manifests itself as the Higgs boson and gives mass to the elementary particles.

• The discovery of the Higgs boson at the LHC closes the chapter of the Standard Model and poses new, more puzzling questions that call for building energy and intensity-frontier colliders.

The Standard Model cannot explain several observations such as:

i) Evidence for dark matter

ii) Prevalence of matter over antimatter

iii) The neutrino masses.

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