Energy, Rapidity and Transverse Momentum Dependence of Multiplicity Fluctuations in Heavy Ion Collisions at CERN SPS

Multiplicity fluctuations in the forward hemisphere were studied for positively, negatively and all charged hadrons produced in central Pb+Pb collisions at 20A, 30A, 40A, 80A and 158A GeV. The multiplicity distributions and their scaled variances are presented as a function of collision energy, rapidity and transverse momentum. The distributions have a bell-like shape and the scaled variance changes monotonously with energy in the range from 0.8 to 1.2. No indication of the critical point is observed. The string-hadronic model UrQMD reproduces results on the scaled variance. The predictions of the hadron-resonance gas model obtained within the grand-canonical and canonical ensembles for the scaled variance disagree with the data.