Disentangling effects of collision geometry and symmetry energy in U+U collisions

Abstract

Effects of the collision geometry on experimental observables that are known to be sensitive to the high-density behavior of nuclear symmetry energy are examined in U $+$ U collisions at 0.52 GeV/nucleon using an isospin- and momentum-dependent interaction within the framework of the isospin-dependent Boltzmann-Uehling-Uhlenbeck (IBUU) transport model. It is found that the neutron-proton differential flow in tip-tip collisions and the difference of neutron and proton elliptic flow in body-body collisions are more sensitive to the symmetry energy at suprasaturation densities compared with collisions of spherical nuclei of the same masses. In addition, the $n/p$ ratio of preequilibrium nucleons is found to be slightly more sensitive to the symmetry energy in tip-tip collisions, and the collision geometry affects the ${\ensuremath{\pi}}^{\ensuremath{-}}/{\ensuremath{\pi}}^{+}$ ratio significantly.