Implications of the measurement of pulsars with two solar masses for quark matter in compact stars and HIC. A NJL model case study

Abstract: The precise measurement of the high masses of the pulsars PSR J1614-2230 (M_{1614}=1.97 +- 0.04 solar masses) and PSR J0348-0432 (M_{0348}=2.01 +- 0.04 solar masses) provides an important constraint for the equation of state of cold, dense matter and is suited to give interesting insights regarding the nature and existence of the possible phase transition to deconfined quark matter in the cores of neutron stars. We analyze the stability and composition of compact star sequences for a class of hybrid nuclear - quark-matter equations of state. The quark matter phase is described in the framework of a standard color superconducting 3-flavor Nambu-Jona-Lasinio model and the hadronic phase is given by the Dirac-Brueckner-Hartree-Fock equation of state for the Bonn-A potential. The phase transition is obtained by a Maxwell construction. Within this model setup we aim to constrain otherwise not strictly fixed parameters of the NJL model, namely the coupling strengths in the vector meson and diquark interaction channels. We perform this investigation for two different parameterizations characterized by a different scalar coupling constant. The analysis of flow data obtained in heavy-ion collisions resulted in a further constraint which we account for in our discussion. Massive hybrid stars with extended quark matter cores can be obtained in accordance with all of the considered constraints.