Particle accelerator delivers first results for heavy atoms
Physics comes a step closer to the Big Bang
Material comparable to that found in the universe just few microseconds after the Big Bang, has been made at the particle accelerator in Geneva. Physicists from Utrecht University and FOM-Nikhef have contributed to one of the first publications about the properties of this plasma, created during collisions of heavy atomic nuclei in the particle accelerator. The article appeared on 13 December in the scientific journal Physical Review Letters.
Besides searching for the Higgs particle, the CERN particle accelerator is also used for research into the Big Bang. The energy that heavy atoms acquire during this is almost 14 times as much as was possible until very recently, and brings the physicists to the situation that existed just a few microseconds after the Big Bang. When this high energy is used to fire lead nuclei at each other, a plasma is created that consists of elementary particles packed very closely together. A few weeks ago, the first measurements into the properties of this rapidly expanding plasma were made using the ALICE detector.
Frictionless fluid
In the accelerator, the particles never collide in an absolute straight line with each other. Consequently, the plasma created during this small 'Big Bang' expands in a preferred direction. Measuring this preferred direction (the so-called elliptic flow) allows the expansion of the plasma to be determined. For heavy atoms, the researchers have now demonstrated that the effect of the elliptic flow is even stronger than for collisions with lower energies. Main author Prof. Raimond Snellings from Utrecht University: "Due to the strong preferred direction of the explosion, this plasma behaves in a manner very similar to that of a near-frictionless fluid."
Building blocks of all material
In further research, the physicists hope to learn more about the plasma and the behaviour of the elementary particles, the building blocks of all material in the universe. Co-author Prof. Thomas Peitzmann from Utrecht University: "After these initial publications, more detailed analyses will follow. Nevertheless, these results have already clearly refuted theories which predicted that the plasma would behave like a gas. And the lack of friction indicates that there is an incredible amount of interaction between the elementary particles in the plasma."
Publication
Elliptic flow of charged particles in Pb-Pb collisions at 2.76 TeV, Physical Review Letters, 13 December 2010.
Further information
Vanessa Mexner, (020) 592 50 75.