Confinement versus color superconductivity: a lattice investigation

The QCD phase diagram as function of the temperature and the baryon chemical potential is the object of many theoretical and experimental investigations. At a high chemical potential, QCD is in the deconfined phase with quarks forming a Fermi surface. It turns out that the gluon induced quark interaction is attractive in the diquark channel [1] generating a Cooper instability of the Fermi surface and leading to color superconductivity [2] (CSC). At the critical value of the chemical potential, the confining forces turn the Fermi surface of quarks into a Fermi surface of hadrons. Several proposals for a description of matter close to the confinement regime have been made: a chiral restored phase might occur in which vector mesons are the light excitations [3]. Alternatively, it might appear that the hadrons smoothly convert into quarks moving in a diquark condensate [4,5].