Spheroidal expansion and freeze-out geometry of heavy-ion collisions in the few-GeV energy regime

A spheroidal model of the expansion of hadronic matter produced in heavy-ion collisions in the few-GeV energy regime is proposed. It constitutes an extension of the spherically symmetric Siemens-Rasmussen blastwave model used in our previous works. The spheroidal form of the expansion, combined with a single-freeze-out scenario, allows fora significantly improved description of both the transverse-mass and the rapidity distributions of the produced particles. With the model parameters determined by the hadronic abundances and spectra, we make further predictions of the pion Hanbury-Brown-Twiss correlation radii that turn out to be in a qualitative agreement with the measured ones. The overall successful description of the data supports the concept of spheroidal symmetry of the produced hadronic systems in this energy range.