Isospin Diffusion and the Nuclear Symmetry Energy in Heavy Ion Reactions

Using symmetric ¹¹²Sn+¹¹²Sn, ¹²⁴Sn+¹²⁴Sn collisions as references, we probe isospin diffusion in peripheral asymmetric ¹¹²Sn+¹²⁴Sn, ¹²⁴Sn+¹¹²Sn systems at an incident energy of E/A=50 MeV. Isoscaling analyses imply that the quasiprojectile and quasitarget in these collisions do not achieve isospin equilibrium, permitting an assessment of isospin transport rates. We find that comparisons between isospin sensitive experimental and theoretical observables, using suitably chosen scaled ratios, permit investigation of the density dependence of the asymmetry term of the nuclear equation of state.