Bose-Einstein correlations of pion pairs in central Pb+Pb collisions at CERN SPS energies

摘要

Measurements of Bose-Einstein correlations of pion pairs in central Pb+Pbcollisions were performed with the NA49 detector at the CERN SPS for beamenergies of 20A, 30A, 40A, 80A, and 158A GeV. Correlation functions weremeasured in the longitudinally co-moving ``out-side-long'' reference frame as afunction of rapidity and transverse momentum in the forward hemisphere of thereaction. Radius and correlation strength parameters were obtained from fits ofa Gaussian parametrization. The results show a decrease of the radiusparameters with increasing transverse momentum characteristic of strong radialflow in the pion source. No striking dependence on pion-pair rapidity or beamenergy is observed. Static and dynamic properties of the pion source areobtained from simultaneous fits with a blast-wave model to radius parametersand midrapidity transverse momentum spectra. Predictions of hydrodynamic andmicroscopic models of Pb+Pb collisions are discussed.