Net-baryon number distributions and the QCD phase diagram

Net-proton multiplicity distributions obtained by the STAR collaboration are analyzed in the grand canonical approach. A method of finding the baryon chemical potential ${\mu }_B$ immediately from such distributions is applied for the first time. The obtained values of ${\mu }_B$ are consistent both with those determined earlier using the statistical thermal model and with the results of the fit based on the Hadron Resonance Gas (HRG) model. We propose a criterion of thermalization of fireballs produced in heavy-nuclei collisions.