Meson Mass at Large Baryon Chemical Potential in Dense QCD

We reexamine the quark mass induced term in chiral Lagrangian in color-flavor locking phase in dense QCD, and show that the meson mass term is determined by three independent invariants under chiral-axial symmetry, and a meson mass is given in terms of the quark mass, gap, and the chemical potential by $m_{\pi }^2\sim m_q^2\mathrm{\Delta }\bar{\mathrm{\Delta }}\mathrm{/}{\mu }^2\ln ({\mu }^2\mathrm{/}{\mathrm{\Delta }}^2)$. Thus mesons become massless as $\mu \to \mathrm{\infty }$.