Scientists have recreated the universe’s ‘primordial soup’ in miniature format by colliding lead atoms with extremely high energy in the world’s most powerful particle accelerator, the Large Hadron Collider (LHC) at CERN.
At CERN, the European Organization for Nuclear Research, physicists and engineers are probing the fundamental structure of the universe. They use the world’s largest and most complex scientific instruments to study the basic constituents of matter – the fundamental particles. The particles are made to collide together at close to the speed of light. The process gives the physicists clues about how the particles interact, and provides insights into the fundamental laws of nature.
The primordial soup is a so-called quark-gluon plasma and researchers from the Niels Bohr Institute in Denmark, among others, have measured its liquid properties with great accuracy at the LHC’s top energy.
A few billionths of a second after the Big Bang, the universe was made up of a kind of extremely hot and dense primordial soup of the most fundamental particles, especially quarks and gluons. This state is called quark-gluon plasma.
By colliding lead nuclei at a record-high energy of 5.02 TeV in LHC, the 27 km-long LHC at CERN in Geneva, it has been possible to recreate this state in the ALICE experiment’s detector and measure its properties.
The analyses of the collisions make it possible, for the first time, to measure the precise characteristics of quark-gluon plasma at the highest energy ever and to determine how it flows.
The focus has been on the quark-gluon plasma’s collective properties, which show that this state of matter behaves more like a liquid than a gas, even at the very highest energy densities.
The new measurements make it possible to determine the viscosity of this exotic fluid with great precision.
The experimental method is very advanced and is based on the fact that when two spherical atomic nuclei are shot at each other and hit each other a bit off centre, quark-gluon plasma is formed with a slightly elongated shape somewhat like an American football.
This means that the pressure difference between the centre of this extremely hot ‘droplet’ and the surface varies along the different axes.
Founded in 1954, the CERN laboratory sits astride the Franco-Swiss border near Geneva. It was one of Europe’s first joint ventures and now has 21 member states.