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CERN collides heavy nuclei at new record high energy

Staff writer |
The world's most powerful accelerator, the 27 km long Large Hadron Collider (LHC) operating at CERN in Geneva established collisions between lead nuclei, this morning, at the highest energies ever.

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The LHC has been colliding protons at record high energy since the summer, but now the time has now come to collide large nuclei (nuclei of lead, Pb, consist of 208 neutrons and protons).

The experiments aim at understanding and studying the properties of strongly interacting systems at high densities and thus the state of matter of the Universe shortly after the Big Bang.

In the very beginning, just a few billionths of a second after the Big Bang, the Universe was made up of an extremely hot and dense 'primordial soup' consisting of the fundamental particles, especially quarks and gluons. This state is called the quark-gluon-plasma (QGP).

Approximately one millionth of a second after the Big Bang, quarks and gluons became confined inside the protons and the neutrons, which are the present day constituents of the atomic nuclei.

The so-called strong force, mediated by the gluons, binds the quarks to each other and - under normal circumstances, trap them inside the nuclear particles.

It is however, possible to recreate a state of matter consisting of quarks and gluons, and which behaves as a liquid, in close imitation of the state of matter prevailing in the very early universe.

It is this state that has now been realised at the highest temperatures ever attained in collisions using lead ions from the LHC accelerator at CERN.

"The collision energy between two nuclei reaches 1000 TeV. This energy is that of a bumblebee hitting us on the cheek on a summer day. But the energy is concentrated in a volume that is approximately 10-27 (a billion-billion-billion) times smaller.

"The energy concentration (density) is therefore tremendous and has never been realised before under terrestrial conditions," explains Jens Jørgen Gaardhøje, professor at the Niels Bohr Institute at the University of Copenhagen and head of the Danish research group within the ALICE experiment at CERN.


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