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 $m_{\pi}^2\sim m_q^2\Delta^2/\mu^2\ln(\mu^2/\Delta^2)$. Thus mesons become massless as $\mu\to\infty$.