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Register a new userStudy of High Energy Heavy-Ion Collisions in a Relativistic BUU-Approach with Momentum-Dependent Mean-Fields
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We introduce momentum-dependent scalar and vector fields into the Lorentz covariant relativistic BUU- (RBUU-) approach employing a polynomial ansatz for the relativistic nucleon-nucleon interaction. The momentum-dependent parametrizations are shown to be valid up to about 1 GeV/u for the empirical proton-nucleus optical potential. We perform numerical simulations for heavy-ion collisions within the RBUU-approach adopting momentum-dependent and momentum-independent mean-fields and calculate the transverse flow in and perpendicular to the reaction plane, the directivity distribution as well as subthreshold K+-production. By means of these observables we discuss the particular role of the momentum-dependent forces and their implications on the nuclear equation of state. We find that only a momentum-dependent parameter-set can explain the experimental data on the transverse flow in the reaction plane from 150 - 1000 MeV/u and the differential K+-production cross sections at 1 GeV/u at the same time.
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A key ingredient of hydrodynamical modeling of relativistic heavy ion collisions is thermal initial conditions, an input that is the consequence of a pre-thermal dynamics which is not completely understood yet. In the paper we employ a recently developed energy-momentum transport model of the pre-thermal stage to study influence of the alternative initial states in nucleus-nucleus collisions on flow and energy density distributions of the matter at the starting time of hydrodynamics. In particular, the dependence of the results on isotropic and anisotropic initial states is analyzed. It is found that at the thermalization time the transverse flow is larger and the maximal energy density is higher for the longitudinally squeezed initial momentum distributions. The results are also sensitive to the relaxation time parameter, equation of state at the thermalization time, and transverse profile of initial energy density distribution: Gaussian approximation, Glauber Monte Carlo profiles, etc. Also, test results ensure that the numerical code based on the energy-momentum transport model is capable of providing both averaged and fluctuating initial conditions for the hydrodynamic simulations of relativistic nuclear collisions.
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