Phys. Rev. C Phys. Rev. C Bose-Einstein correlations of $\pi^{-}\pi^{-}$ pairs in central Pb+Pb collisions at 20A,30A,40A,80A, and 158A GeV Alt C. Frankfurt U. Anticic T. Boskovic Inst., Zagreb Baatar B. Dubna, JINR Barna D. Budapest, RMKI Bartke J. Cracow, INP Betev L. CERN Bialkowska H. Warsaw, Inst. Nucl. Studies Blume C. Frankfurt U. Boimska B. Warsaw, Inst. Nucl. Studies Botje M. NIKHEF, Amsterdam Bracinik J. Comenius U. Bramm R. Frankfurt U. Buncic P. CERN Cerny V. Comenius U. Christakoglou P. Athens U. Chung P. SUNY, Stony Brook, Chem. Dept. Chvala O. Charles U. Cramer J.G. Washington U., Seattle Csato P. Budapest, RMKI Dinkelaker P. Frankfurt U. Eckardt V. Munich, Max Planck Inst. Flierl D. Frankfurt U. Fodor Z. Budapest, RMKI Foka P. Darmstadt, GSI Friese V. Darmstadt, GSI Gal J. Budapest, RMKI Gazdzicki M. Frankfurt U. Jan Kochanowski U. Genchev V. Sofiya, Inst. Nucl. Res. Georgopoulos G. Athens U. Gladysz E. Cracow, INP Grebieszkow K. Warsaw U. of Tech. Hegyi S. Budapest, RMKI Hohne C. Darmstadt, GSI Kadija K. Boskovic Inst., Zagreb Karev A. Munich, Max Planck Inst. Kikola D. Warsaw U. of Tech. Kliemant M. Frankfurt U. Kniege S. Frankfurt U. Kolesnikov V.I. Dubna, JINR Kornas E. Cracow, INP Korus R. Jan Kochanowski U. Kowalski M. Cracow, INP Kraus I. Darmstadt, GSI Kreps M. Comenius U. Laszlo A. Budapest, RMKI Lacey R. SUNY, Stony Brook, Chem. Dept. van Leeuwen M. NIKHEF, Amsterdam Levai P. Budapest, RMKI Litov L. Sofiya U. Lungwitz B. Frankfurt U. Makariev M. Sofiya U. Malakhov A.I. Dubna, JINR Mateev M. Sofiya U. Melkumov G.L. Dubna, JINR Mischke A. NIKHEF, Amsterdam Mitrovski M. Frankfurt U. Molnar J. Budapest, RMKI Mrowczynski St. Jan Kochanowski U. Nicolic V. Boskovic Inst., Zagreb Palla G. Budapest, RMKI Panagiotou A.D. Athens U. Panayotov D. Sofiya U. Petridis A. Athens U. Peryt W. Warsaw U. of Tech. Pikna M. Comenius U. Pluta J. Warsaw U. of Tech. Prindle D. Washington U., Seattle Puhlhofer F. Philipps U. Marburg Renfordt R. Frankfurt U. Roland C. MIT Roland G. MIT Rybczynski M. Jan Kochanowski U. Rybicki A. Cracow, INP CERN Sandoval A. Darmstadt, GSI Schmitz N. Munich, Max Planck Inst. Schuster T. Frankfurt U. Seyboth P. Munich, Max Planck Inst. Sikler F. Budapest, RMKI Sitar B. Comenius U. Skrzypczak E. Warsaw U. Slodkowski M. Warsaw U. of Tech. Stefanek G. Jan Kochanowski U. Stock R. Frankfurt U. Strabel C. Frankfurt U. Strobele H. Frankfurt U. Susa T. Boskovic Inst., Zagreb Szentpetery I. Budapest, RMKI Sziklai J. Budapest, RMKI Szuba M. Warsaw U. of Tech. Szymanski P. CERN Warsaw, Inst. Nucl. Studies Trubnikov V. Warsaw, Inst. Nucl. Studies Varga D. Budapest, RMKI CERN Vassiliou M. Athens U. Veres G.I. Budapest, RMKI MIT Vesztergombi G. Budapest, RMKI Vranic D. Darmstadt, GSI Wetzler A. Frankfurt U. Wlodarczyk Z. Jan Kochanowski U. Wojtaszek A. Jan Kochanowski U. Yoo I.K. Pusan Natl. U. Zimanyi J. Budapest, RMKI 2008 77 Measurements of Bose--Einstein correlations of pion pairs in central Pb+Pb collisions were performed with the NA49 detector at the CERN SPS for beam energies of 20A, 30A, 40A, 80A, and 158A GeV. Correlation functions were measured in the longitudinally co-moving "out-side-long" refere nce frame as a function of rapidity and transverse momentum in the forward hemisphere of the reaction. Radius and correlation strength parameters were obtained from fits of a Gaussian parametrization. The results show a decrease of the radius parameters with increasing transverse momentum characteristic of strong radial flow in the pion source. No striking dependence on pion-pair rapidity or beam energy is observed. Static and dynamic properties of the pion source are obtained from simultaneous fits with a blast-wave model to radius parameters and midrapidity transverse momentum spectra. Predictions of hydrodynamic and microscopic models of Pb+Pb collisions are discussed. research-article