Higher moments of net baryon distribution as probes of the QCD critical point

It is crucially important to find an acceptance and late collision process independent observable in searching for the possible critical point predicted by QCD. By utilizing a multiphase transport (AMPT) model and ultrarelativistic quantum molecular dynamics (UrQMD) model, we study the centrality and evolution time dependence of higher moments of net baryon distribution in Au+Au collisions at √sNN=17.3 GeV. The results suggest that kurtosis and skewness are less sensitive to the acceptance effect and late collision process. Thus, they should be good observables providing the information on the early stage of a heavy-ion collision. In addition, our study shows that the product of kurtosis times σ² of the net proton distribution is quite different from that of the net baryon distribution when the collision energy is lower than √sNN=20 GeV, the Monte Carlo calculations on kurtosis·σ² have a deviation from the theoretical predictions.