QCD equation of state at finite density with a critical point from an alternative expansion scheme.

    In Ref. [1], results for the QCD equation of state from the lattice Taylor expansion were combined with the 3D Ising model critical behavior, to build a family of equations of state which match the first principle results and contain a critical point in the expected universality class for QCD. This family of equations of state was limited to chemical potentials 0 ≤ μ_B ≤ 450 MeV, due to the limitations of the Taylor expansion. In Ref. [2],  an alternative expansion scheme was introduced, for extrapolating the lattice QCD equation of state to finite chemical potential. In this research, we combine these two approaches to obtain a family of equations of state in the range 0 ≤ μ_B ≤ 700 MeV and  30 MeV ≤ T ≤ 800  MeV, that match the lattice QCD results at small density and contain a 3D-Ising model critical point. With these new equations of state, we substantially extend the coverage of the QCD phase diagram.

Our open-source code allows the user to choose the position and strength of the critical point. Our results provide input for hydrodynamical simulations at finite T and unprecedentedly large μ_B and will help constrain the location of the critical point through a comparison with experimental data from the Second Beam Energy Scan at RHIC.