Scalar-isoscalar excitation in dense quark matter

Abstract

We study the spectrum of scalar-isoscalar excitations in the color-flavor locked phase of dense quark matter. The sigma meson in this phase appears as a four-quark state (of diquark and antidiquark) with a well-defined mass and extremely small width, as a consequence of its small coupling to two pions. The quark particle/hole degrees of freedom also contribute significantly to the correlator just above the threshold $2\ensuremath{\Delta},$ where $\ensuremath{\Delta}$ is the superconducting gap.