Searching for the QCD critical point in AA collisions at CERN SPS

Abstract

We investigate the transverse momentum correlations of pairs of opposite charged pions near their production threshold. Through intermittency analysis, we search for power-law dependence on observation scale, as dictated by critical QCD. We analyze the data on the most central collisions in four A systems (A = p, C, Si, Pb) at maximum SPS energy. We find a significant effect for the SiSi system approaching in size the critical QCD predictions as measured by the intermittency index ϕ2. Absence of this effect in the (π−, π−) sector of the SiSi system gives further support that the observed behavior in the isoscalar mode is of critical origin.