Behavior of Hadrons at Finite Density -- Lattice Study of Color SU(2) QCD

Using two-color lattice QCD with Wilson fermions, we report a study of the finite baryon number density system with two-flavors. First we investigate the Polyakov line and thermodynamical uantities in the $(\kappa,\mu)$ plane, where $\kappa$ and $\mu$ are the hopping parameter and chemical potential in the fermion action, respectively. Then we calculate propagators of meson ($\bar{q}\Gamma q$) and baryon ($q\Gamma q$) states. We find that the vector meson propagators are strongly modified in large $\mu$ regions, indicating the reduction of the mass. This anomalous behavior of the vector meson is observed for the first time in lattice QCD.