Scientists from the Niels Bohr Institute, University of Copenhagen, and their colleagues from the international ALICE collaboration recently collided Xenon nuclei, in order to gain new insights into the properties of the Quark-Gluon Plasma (the QGP) – the matter that the universe consisted of up to a microsecond after the Big Bang.
The QGP, as the name suggests, is a special state consisting of the fundamental particles, the quarks, and the particles that bind the quarks together, the gluons. The result was obtained using the ALICE experiment at the 27 km long superconducting Large Hadron Collider (LHC) at CERN. The result is now published in Physics Letters
With collisions approaching the speed of light and enormous energy (5.44 TeV) a fireball lasting a mere 10-22 seconds was generated at temperatures of several thousand billion degrees.
Under these conditions a plasma of hadron components is created consisting of quarks and gluons. the density of the plasma is very high and forms a special state of matter known as the strongly interacting QGP.
The experiments suggest that the primordial matter, the instant before atoms formed, behaves like a liquid that can be described in terms of hydrodynamics.
The experiments involved studying the spatial distribution of the many thousands of particles that emerge from the collisions when the quarks and gluons have been trapped into the particles that the Universe consists of today. This reflects not only the initial geometry of the collision, but is sensitive to the properties of the QGP.
Source: Neils Bohr Institute
Anisotropic flow in Xe–Xe collisions at 5.44 TeV
The first measurements of anisotropic flow coefficients for mid-rapidity charged particles in Xe–Xe collisions at TeV are presented. Comparing these measurements to those from Pb–Pb collisions at TeV, is found to be suppressed for mid-central collisions at the same centrality, and enhanced for central collisions. The values of are generally larger in Xe–Xe than in Pb–Pb at a given centrality. These observations are consistent with expectations from hydrodynamic predictions. When both and are divided by their corresponding eccentricities for a variety of initial state models, they generally scale with transverse density when comparing Xe–Xe and Pb–Pb, with some deviations observed in central Xe–Xe and Pb–Pb collisions. These results assist in placing strong constraints on both the initial state geometry and medium response for relativistic heavy-ion collisions.