In ultra-relativistic heavy ion collisions at CERN's LHC accelerator, a new state of matter is formed: the quark-gluon plasma (QGP). It is a kind of very dense and hot "soup" containing only the most elementary constituents of matter. A few microseconds after the Big Bang, the Universe would have passed through this state.
According to the ALICE collaboration at LHC (CERN), certain rare proton collisions have properties that are similar to those of a quark–gluon plasma. In the past, these properties had been observed for collisions of heavy nuclei only.
Le Large Hadron Collider (LHC) au CERN a récemment mené à bien le programme de collisions de protons sur des noyaux de plomb.
The first lead-lead collision results have been published
After almost a year collecting data from proton-proton collisions, the LHC at CERN began the injection of lead ions at the beginning of November, with the first collisions obtained on November 8. The energy in the nucleon-nucleon center of mass is 2.76 TeV, around ten times greater than that achieved previously by the RHIC in Brookhaven USA.
Monday, 23 November 2009, marked the first particle beam collision inside the large detectors of the LHC. ALICE saw its first collisions at an energy of 900 GeV, enabling it to check for correct operation of the 18 large detectors which comprise it.


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