Chiral symmetry breaking, color superconductivity and gapless modes in 2SC+s quark matter

Abstract

We investigate the chiral symmetry breaking and color superconductivity in color and electric charge neutral quark matter including strange quarks (2SC+s quark matter) in a Nambu-Jona-Lasinio model using a variational method. The methodology involves an explicit construction of a variational ground state and minimisation of the thermodynamic potential. Simultaneous existence of a mass gap and a superconducting gap is seen in a small window of quark chemical potential within the model when charge neutrality conditions are not imposed. Enforcing color and electric charge neutrality conditions gives rise to the existence of gapless modes in 2SC+s quark matter depending upon the magnitude of the gap and the difference of the chemical potentials of the condensing quarks. Within the window for gapless modes, it is seen that the strange quark density can be as large as 30%--40% of the number density of either of the condensing light quarks.