The nuclear symmetry energy, which is important for asymmetric nuclear systems including rare isotopes and neutron stars, has been studied through both experimental and theoretical approaches, spanning a range of densities from below and above normal nuclear matter density. In the past decade, significant constraints on the density dependence have been obtained in the subsaturation density region, from Heavy Ion Collision (HIC) experiments as well as experiments probing nuclear structure. On the other hand, very little has been determined about the symmetry energy at suprasaturation densities; experimentally, this density region is only accessible in HICs. It is therefore important to understand how to extract nuclear symmetry energy information from HIC at high energies where high density nuclear matter is created in a very brief instant.Symmetry energy constraints from HICs are determined by comparing experimental observables with those calculated using transport models. The goals of this dissertation are to identify the observables most sensitive to the symmetry energy strength, the effective mass splitting, and the in-medium nucleon-nucleon cross sections, $\sigma_{NN}$, at the region just above saturation density which can be created with heavy ion beams available at NSCL. With better constraints in place, the predictive power of transport models will improve. Recent constraints from HIC experiments have relied on symmetric systems, which are predicted to be sensitive to both the density- and the momentum-dependence of the symmetry potentials. In the study of the nuclear equation of state, asymmetric systems have proven to be more effective at low energy in exploring sensitivities to nucleon-nucleon collisions, which is an important input to any transport model.In this work, particles that were emitted from Ca+Sn systems, with a $^{48}$Ca beam impinging on $^{112}$Sn or $^{124}$Sn targets are measured. The experimental data were compared to predictions from the Improved Molecular Dynamics model with Skyrme interactions (ImQMD-Sky). Four Skyrme parameter sets were chosen that span current constraints on the density dependence of the symmetry energy and on the nucleon effective mass splitting, $m^*_n \neq m^*_p$, which results from the momentum dependent interaction potentials. ImQMD-Sky calculations were repeated using an alternate form for $\sigma_{NN}$.The yields and ratios of both free and coalescence invariant experimental spectra, constructed as a function of the transverse momentum, were contrasted to those simulated by ImQMD-Sky. To select the overlap region between beam and target nuclei, a mid-rapidity cut was taken in the analysis. The parameter sets included in this analysis did not show a significant sensitivity to the symmetry energy strength, but do suggest that the neutron-to-proton ratio bears a large sensitivity both to the nucleon effective mass splitting and the $\sigma_{NN}$ forms used in the calculations.Comparison to the measured coalescence invariant spectra suggests a better agreement with calculations employing effective masses that are greater for neutrons than for protons and a set of isospin-dependent $\sigma_{NN}$. The results in this analysis for the asymmetric Ca+Sn reaction are compared with previous results for a symmetric Sn+Sn reaction at 120 AMeV, which shows an opposite conclusion for low energy particles.
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