Chromodynamic theory predicts that in extreme temperature and energy density, a new state of nuclear matter should be formed : a Quark and Gluon Plasma (QGP). This state of plasma is supposed to have existed at the very early stages of the universe that has then evolved to the cold state that we know today. The QGP should be recreated in a laboratory in ultra-relativistic heavy ion collisions at RHIC, and most of all at the energy of the large hadron collider the LHC that started at CERN in 2009. s LHC qui entrera en fonctionnement en 2007 au CERN.
Within the 4 experiments that have been build at the LHC : ALICE, ATLAS, CMS et LHCb, ALICE is the only one exclusivly dedicated to heavy ion collusions. Experimental measurement of the QGP and its complete quantitative description will be done studying the collisions products such as hadrons, electrons, muons and photons measured with the different detectors and sub-detectors. In particular the muons from the resonances decays of heavy quarks J/Ψ, Ψ', Υ, Υ' et Υ'' will be studied with the muon spectrometer, and the photons with the clorimeter EMCal.
Our group works mainly with the EMCal today, but also combining information of othe subsystems such as the tracking systems. More information on our actuvities have been gathered here : ALICE EMCAL. In the begining of our implicatio in the ALICE experiment, the group took care of the muon spectrometer alignement. More details on this activity is here ALICE GMS.