Photon Radiation from Anisotropic Nuclear Matter produced in Heavy-Ion Collisions at Fermi Energy

Heavy-ion collisions (HICs) are broadly used to examine the properties of nuclear matter under extreme conditions of density and temperature. Electromagnetic radiation in the form of photons or dileptons has long served as a penetrating probe of strongly interacting matter because of its ability to escape from the nuclear medium mostly unperturbed by final-state interactions. In this work, we focus on HICs at Fermi energies, where, in particular, the degree of thermalization remains an open question. We first briefly review our analysis of time dependence of thermodynamic properties of Ca-Ca(35AMeV) collisions using a coarse-graining approach to Constrained Molecular Dynamics simulations; significant non-thermal features caused by the initial motion of the incoming nuclei have been quantified in terms of anisotropic distribution functions. We incorporate these distributions into the calculation of photon rates from nucleon-nucleon Bremsstrahlung and discuss how the non-thermal features manifest themselves. The rates are then convoluted over the space-time evolution of Ca-Ca(35AMeV) collisions, and the resulting photon spectra are compared to experimental spectra in an attempt to shed light on their composition of collective and local emission sources.