Azimuthal-sensitive three-dimensional HBT radius in Au-Au collisions at $E_{beam} = 1.23$$A$ GeV by the IQMD model

Abstract

We used an Isospin dependent Quantum Molecular Dynamics (IQMD) model to simulate Au + Au collisions at beam energy E beam = 1.23A GeV, which corresponds to center of mass energy √ sNN = 2.4 GeV. Firstly, we obtained reasonable rapidity and transverse mass spectra of π − and π + as well as "apparent" temperature parameters in comparison with the HADES data. Then by calculating three-dimensional Hanbury Brown and Twiss (HBT) radius of same charged pion-pairs, we obtained the square difference of outward radius and sideward radius, i.e. R 2 out − R 2 side , as well as the freeze-out volume (V f o ), which were basically consistent with the trend of HADES experimental results. The azimuthal dependence of the HBT radii was also calculated by a matrix method, and corrected by the rotation matrix. In addition, the eccentricities of the xy-and zy-planes of pion-pair emissions were also extracted for different pair transverse momentum and collision centrality, which show that the xy-eccentricity increases with pair transverse momentum as well as centrality but not for zy-eccentricity, indicating a more asymmetric transverse emission of particle-pairs with higher transverse momentum in off-central collisions.

Effects of a phase transition on two-pion interferometry in heavy ion collisions at $$\sqrt {{s_{{\rm{NN}}}}} = 2.4 - 7.7\,\,{\rm{GeV}}$$

“…The origin of the HBT radii decreases with the increasing transverse momentum has been discussed in many works. We refer interested readers to related works for the details [87,[89][90][91][92]. At √ s NN = 2.4 GeV, using the soft Skyrme EoS (K 0 = 200 MeV) is added for comparison.…”