%0 Journal Article %T Canonical partition function and finite density phase transition in lattice QCD %A Shinji Ejiri %J Physics %D 2008 %I arXiv %R 10.1103/PhysRevD.78.074507 %X We discuss the nature of the phase transition for lattice QCD at finite temperature and density. We propose a method to calculate the canonical partition function by fixing the total quark number introducing approximations allowed in the low density region. An effective potential as a function of the quark number density is discussed from the canonical partition function. We analyze data obtained in a simulation of two-flavor QCD using p4-improved staggered quarks with bare quark mass $m/T = 0.4$ on a $16^3 \times 4$ lattice. The results suggest that the finite density phase transition at low temperature is of first order. %U http://arxiv.org/abs/0804.3227v3