Collisions involving {112Sn} and {124Sn} nuclei have been simulated with the improved quantum molecular dynamics transport model. The results of the calculations reproduce isospin diffusion data from two different observables and the ratios of neutron and proton spectra. By comparing these data to calculations performed over a range of symmetry energies at saturation density and different representations of the density dependence of the symmetry energy, constraints on the density dependence of the symmetry energy at subnormal density are obtained. The results from the present work are compared to constraints put forward in other recent analyses.

%B Physical Review Letters %V 102 %P 122701 %8 03/2009 %G eng %0 Journal Article %J Physics Letters B %D 2008 %T The influence of cluster emission and the symmetry energy on neutron-proton spectral double ratios %A Yingxun Zhang %A P. Danielewicz %A M. Famiano %A Li, Z. %A W. G. Lynch %A M. B. Tsang %XThe emissions of neutrons, protons and bound clusters from central {124Sn} + {124Sn} and {112Sn} + {112Sn} collisions are simulated using the Improved Quantum Molecular Dynamics model for two different density-dependent symmetry-energy functions. The calculated neutron-proton spectral double ratios for these two systems are sensitive to the density dependence of the symmetry energy, consistent with previous work. Cluster emission increases the double ratios in the low energy region relative to values calculated in a coalescence-invariant approach. To circumvent uncertainties in cluster production and secondary decays, it is important to have more accurate measurements of the neutron-proton ratios at higher energies in the center of mass system, where the influence of such effects is reduced.

%B Physics Letters B %V 664 %P 145–148 %8 02/2008 %G eng