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 p, rather than the chemical potential p. We apply this method to the determination of the phase diagram of four-flavor QCD. For a pion mass m(pi) similar to 350 MeV, the first-order transition between the hadronic and the plasma phase gives rise to a co-existence region in the T-p 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 mu up to 2T. Our T-mu phase diagram agrees with the literature when mu/T less than or similar to 1. At larger chemical T potential, we observe a bending down of the phase boundary. We compare the free energy in the confined and deconfined phase with predictions from a hadron resonance gas and from a free massless quark gas respectively.