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Description
We investigate the chemical-potential dependence of hadron spectra in two-color QCD using the first-principles lattice simulations.
In this work, we compute two-point correlation functions for various hadrons by newly including the contributions from disconnected diagrams, and extract the corresponding effective masses.
In the meson sector, the mass hierarchy in the hadronic phase (normal vacuum) is found to be $m_\pi \lesssim m_{\eta} < m_\sigma \mathrm{(noisy)} < m_\rho \sim m_\omega \ll m_{a_1}$, which is similar to that in three-color QCD.
In the superfluid phase, this hierarchy is modified, and with increasing density it changes to $m_\sigma \mathrm{(noisy)} < m_{a_1} < m_\rho < m_\pi \sim m_{\eta} \mathrm{(noisy)} \ll m_{\omega} \mathrm{(noisy)}$.
In the diquark sector, the ordering remains as $m_{NG} \lesssim m_{I=0, S} < m_{I=1, AV} < m_{I=0, PS} \lesssim m_{I=0, V}$ in both phases, and the Nambu–Goldstone mode associated with spontaneous breaking of $U(1)_B$ is confirmed to be nearly massless.
Furthermore, by comparing correlators of chiral partners, we find indications of chiral symmetry restoration at high density.