Mesons and diquarks in neutral color superconducting quark matter with $\beta$-equilibrium

Abstract

The spectrum of meson and diquark excitations in cold color-superconducting (2SC) quark matter is investigated under local color and electric neutrality constraints with $\beta$-equilibrium. A 2-flavored Nambu--Jona-Lasinio type model including a baryon ${\mu }_B$, color ${\mu }_8$, and electric ${\mu }_Q$ chemical potentials is used. Two relations between coupling constants $H$ and $G$ in the diquark- and quark-antiquark channels, correspondingly, are treated, $H=3G/4$ and $H=G$. At $H=3G/4$ the gapless- and at $H=G$ the gapped neutral color superconductivity is realized. It is shown that color and electrical neutrality together with $\beta$-equilibrium lead to a strong mass splitting within the pion isotriplet in the 2SC phase (both gapped and gapless), in contrast with non--neutral matter. It is also shown that the properties of the physical $SU(2{)}_c$-singlet diquark excitation in the 2SC ground state varies for different parameterization schemes. Thus, for $H=3G/4$ one finds a heavy resonance with mass $\sim$ 1100 MeV in the non--neutral (gapped) case, whereas, if neutrality is imposed, a stable diquark with mass $\sim {\mu }_Q\sim$ 200 MeV appears in the gapless 2SC phase. For $H=G$, there is again a resonance (with the mass $\sim$ 300 MeV) in the neutral gapped 2SC phase. Hence, the existence of the stable massive SU(2)${}_c$-singlet diquark excitation is a new peculiarity of the gapless 2SC.

arXiv comment18 pages, 9 figures; version accepted for publication in PRD

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• Properties of the massive Gross-Neveu model with nonzero baryon and isospin chemical potentials
• High density quark matter in the NJL model with dimensional vs. cut-off regularization
• Mass spectrum of diquarks and mesons in the color--flavor locked phase of dense quark matter
• Diquarks in the color--flavor locked phase of dense quark matter
• Two-flavor color superconducting quark stars may not exist
• Dynamical stabilization of runaway potentials at finite density
• Optimized perturbation theory applied to the study of the thermodynamics and BEC-BCS crossover in the three-color Nambu--Jona-Lasinio model
• Color superconductivity in the Nambu Jona-Lasinio model complemented by a Polyakov loop
• Dynamical stabilization of runaway potentials and landscape of vacua at finite density
• How does color neutrality affect collective modes in color superconductors?
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