Probing in-medium effect via giant dipole resonance in the extended quantum molecular dynamics model

Abstract

Rather than using the geometric method employed in the original Extended Quantum Molecular Dynamics (EQMD) model, this article employs a stochastic approach to analyze the collision term and examine the width of the isovector giant dipole resonance (GDR) in ${}^{208}$Pb. Based on the ``soft" EQMD model, which we recently developed, the response and strength functions are self-consistently determined for various symmetry energy coefficients and in-medium reduction factor values. The results confirm that the peak position and GDR width in ${}^{208}$Pb are highly sensitive to the symmetry energy and the in-medium nucleon-nucleon ({\it NN}) cross section. This provides an opportunity to study the nuclear equation of state (EoS) and the medium effect. A significant reduction in free {\it NN} elastic cross sections within the medium is necessary to accurately reproduce the GDR width, as demonstrated by a comparison with the evaluation data.