There is an undiscovered state in quantum chromodynamics (QCD) that describes the “strong force” acting on elementary particles. That is a “Color Glass Condensate (CGC)”. This state is a high-density gluon matter predicted by QCD, and at the same time gives an initial condition of Quark Gluon Plasma (QGP) that appears in high-energy heavy ion collisions. Therefore, CGC is linked to our fundamental understanding of “strong force”. Many experimental studies have been carried out so far, but no clear signal has been obtained. We have developed a highly segmented silicon electromagnetic calorimeter detector “FoCal” that can capture clear signal of CGC under high particle density.
In this research program, FoCal will be constructed and installed to the ALICE experiment at LHC, and the existence of CGC will be experimentally explored by detecting isolated photons, decay photons from neutral mesons and jets by FoCal and the existing ALICE detector. We will elucidate the origin of QGP formation and the mechanism of early thermalization that appear in heavy ion reactions. This is a new international collaboration led by the Japanese team and international collaboration including Utrecht University, Grenoble LPSC.
