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Many flavor approach to study the critical point in finite density QCD

We discuss the QCD critical point at finite density through the study of many flavor QCD, in which two light flavors and Nf massive flavors exist. Performing simulations of QCD with two flavors of improved Wilson fermions, we calculate probability distribution functions of many flavor QCD at finite temperature and density. The dynamical effects of massive flavors and the chemical potential are added using the reweighting technique. From the shape of the distribution functions, we determine the critical surface separating the first order transition and crossover regions in the parameter space of the light and massive quark masses and the chemical potentials. It is found that the critical massive quark mass becomes larger as the chemical potential increases in (2+Nf) flavor QCD. The indication to the (2+1) flavor QCD is then discussed.