Accessibility of Color Superconducting Quark Matter Phases in Heavy-Ion Collisions

We discuss a hybrid equation of state (EoS) that fulfills constraints for mass-radius relationships and cooling of compact stars. The quark matter EoS is obtained from a Polyakov-loop Nambu-Jona-Lasinio (PNJL) model with color superconductivity, and the hadronic one from a relativistic mean field (RMF) model with density-dependent couplings (DD-RMF). For the construction of the phase transition regions we employ here for simplicity a Maxwell construction. We present the phase diagram for symmetric matter which exhibits two remarkable features: (1) a '' nose '' -like structure of the hadronic-to-quark matter phase border with an increase of the critical density at temperatures below T ∼ 150 MeV and (2) a high critical temperature for the border of the two-flavor color superconducting (2SC) phase, Tc > 160 MeV. We show the trajectories of heavy-ion collisions in the plane of excitation energy versus baryon density calculated using the UrQMD code and conjecture that for incident energies of 4 ... 8 AGeV as provided, e.g., by the Nuclotron-M at JINR Dubna or by lowest energies at the future heavy-ion collision experiments CBM at FAIR and NICA at JINR, the color superconducting quark matter phase becomes accessible. (authors)