Phase space and quark mass effects in neutrino emissions in a color superconductor

We study the phase space for neutrino emissions with massive quarks in direct Urca processes in normal and color-superconducting quark matter. We derive in QCD and the Nambu-Jona-Lasinio model the Fermi momentum reduction resulting from Fermi liquid properties which opens up the phase space for neutrino emissions. The relation between the Fermi momentum and chemical potential is found to be p_F≈μ(1-κ) with κ depending on coupling constants. We find in the weak coupling regime that κ is a monotonically increasing function of the chemical potential. This implies quenched phase space for neutrino emissions at low baryon densities. We calculate neutrino emissivities with massive quarks in a spin-one color superconductor. The quark mass corrections are found to be of the same order as the contributions in the massless case, which will bring sizable effects on the cooling behavior of compact stars.