Improved Schwinger-Dyson approach to pairing phenomena and QCD phase diagram

Phase structure and phase transitions in dense QCD are studied using the Cornwall-Jackiw-Tomboulis (CJT) potential in the improved ladder approximation. The gap function, the condensation energy and the structure of Cooper pairs are investigated at finite temperature and density. Due to strong coupling effects at low densities, the gap, critical temperature and their ratio deviate from the weak coupling values. It is shown that the internal structure of Cooper pairs are robust against the thermal effects, despite the fact that the pairs are strongly correlated near the critical temperature. Also, the effect of the strange quark mass, ms on the phase diagram is examined using a simple kinematical criterion. We discuss the behavior of the unlocking line, on which the CFL phase turns into the 2SC phase, through the variation of ms. (author)