Energy dependence of transverse momentum fluctuations in Pb+Pb collisions at the CERN Super Proton Synchrotron (SPS) at 20A to 158A GeV
Abstract
Results are presented on event-by-event fluctuations of transverse momenta pT in central Pb+Pb interactions at 20A, 30A, 40A, 80A, and 158A GeV. The analysis was performed for charged particles at forward center-of-mass rapidity (1.1 < y*π < 2.6). Three fluctuation measures were studied: the distribution of average transverse momentum - M(pT) - in the event, the pT fluctuation measure and two-particle transverse momentum correlations. Fluctuations of pT are small and show no significant energy dependence in the energy range of the CERN Super Proton Synchrotron. Results are compared with QCD-inspired predictions for the critical point, and with the UrQMD model. Transverse momentum fluctuations, similar to multiplicity fluctuations, do not show the increase expected for freeze-out near the critical point of QCD.