Mass spectrum of diquarks and mesons in the color--flavor locked phase of dense quark matter

Understand

The spectrum of meson and diquark excitations of dense quark matter is considered in the framework of the Nambu -- Jona-Lasinio model with three types of massless quarks in the presense of a quark number chemical potential $\mu$.

• We investigate the effective action of meson- and diquark fields both at sufficiently large values of $\mu>\mu_c\approx 330$ MeV, where the color--flavor locked (CFL) phase is realized, and in the chirally broken phase of quark matter ($\mu<\mu_c$).
• In the last case all nine pseudoscalar mesons are Nambu -- Goldstone (NG) bosons, whereas the mass of the scalar meson nonet is twice the dynamical quark mass.
• In the chirally broken phase the pseudoscalar diquarks are not allowed to exist as stable particles, but the scalar diquarks might be stable only at a rather strong interaction in the diquark channel.