Finite density QCD with a canonical approach

We present a canonical method where the properties of QCD are directly obtained as a function of the baryon density ρ, rather than the chemical potential μ. We apply this method to the determination of the phase diagram of four-flavor QCD. For a pion mass mπ∼350 MeV, the first-order transition between the hadronic and the plasma phase gives rise to a co-existence region in the T-ρ plane, which we study in detail, including the associated interface tension. We obtain accurate results for systems containing up to 30 baryons and quark chemical potentials μ, up to 2T. Our T-μ phase diagram agrees with the literature when μT≲1. At larger chemical potential, we observe a “bending down” of the phase boundary. We compare the free energy in the confined and deconfmed phase with predictions from a hadron resonance gas and from a free massless quark gas respectively.