Mesons and diquarks in the color neutral 2SC phase of dense cold quark matter

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The spectrum of meson and diquark excitations of dense color neutral cold quark matter is investigated in the framework of a 2-flavored Nambu--Jona-Lasinio type model, including a quark μ- and color μ₈ chemical potential. It was found out that in the color superconducting (2SC) phase, i.e. at μ>μc=342 MeV, μ₈ aquires rather small values 10 MeV in order to ensure the color neutrality. In this phase the π- and σ meson masses are evaluated around 330 MeV. The spectrum of scalar diquarks in the color neutral 2SC phase consists of a heavy (SUc(2)-singlet) resonance with mass 1100 MeV, four light diquarks with mass 3|μ₈|, and one Nambu --Goldstone boson which is in accordance with the Goldstone theorem. Moreover, in the 2SC phase there are five light stable particles as well as a heavy resonance in the spectrum of pseudo-scalar diquarks. In the color symmetric phase, i.e. for μ<μc, a mass splitting of scalar diquarks and antidiquarks is shown to arise if μ≠ 0, contrary to the case of μ= 0, where the masses of scalar antidiquarks and diquarks are degenerate at the value 700 MeV. If the coupling strength in the pseudo-scalar diquark channel is the same as in the scalar diquark one (as for QCD-inspired NJL models), then in the color symmetric phase pseudo-scalar diquarks are not allowed to exist as stable particles.