Expansion dynamics of Pb?Pb collisions at 40 A GeV/c viewed by negatively charged hadrons

In this paper, we present results on transverse mass spectra and Hanbury–Brown and Twiss correlation functions of negatively charged hadrons, which are expected to be mostly π−, measured in Pb–Pb collisions at 40 A GeV/c beam momentum. Based on these data, the collision dynamics and the spacetime extent of the system at the thermal freeze-out are studied over a centrality range corresponding to the most central 53% of the Pb–Pb inelastic cross-section. Comparisons with freeze-out conditions of strange particles and HBT results from other experiments are discussed.