Pion, σ meson, and diquarks in the two-flavor color-superconducting phase of dense cold quark matter -: art. no. 015201

The spectrum of meson and diquark excitations of dense cold quark matter is investigated within the framework of a Nambu-Jona-Lasinio-type model for light quarks of two flavors. It was found that a first-order phase transition occurs when the chemical potential mu exceeds the critical value mu(c)=350 MeV. Above mu(c), the diquark condensate < qq > forms, breaking the color symmetry of strong interaction. The masses of pi and sigma mesons are shown to grow with the chemical potential mu in the color-superconducting phase, but the mesons themselves become almost stable particles. Moreover, we have found in this phase an abnormal number of three, instead of five, Nambu-Goldstone bosons, together with a color doublet of light stable diquark modes and a color-singlet heavy diquark resonance with mass similar to 1100 MeV. In the color-symmetric phase, i.e., for mu <mu(c), a mass splitting of diquarks and antidiquarks is shown to arise if mu not equal 0, contrary to the case of a vanishing chemical potential, in which the masses of antidiquarks and diquarks are degenerate at the value similar to 700 MeV.