Determination of the mean-field momentum-dependence using elliptic flow

✍ Scribed by Pawel Danielewicz

• Publisher: Elsevier Science
• Year: 2000
• Tongue: English
• Weight: 569 KB
• Volume: 673
• Category: Article
• ISSN: 0375-9474
• DOI: 10.1016/s0375-9474(00)00083-x

✦ Synopsis

Midrapidity nucleon elliptic flow is studied within the Boltzmann-equation simulations of symmetric heavy-ion collisions. The simulations follow a lattice Hamiltonian extended to relativistic transport. It is demonstrated that in the peripheral heavy-ion collisions the high-momentum elliptic flow is strongly sensitive to the momentum dependence of mean field at supranormal densities. The high transverse-momentum particles are directly and exclusively emitted from the high-density zone in the collisions, while remaining particles primarily continue along the beam axis. The elliptic flow was measured by the KaOS Collaboration as a function of the transverse momentum at a number of impact parameters in Bi + Bi collisions at 400, 700, and 1000 MeV/nucleon. The observed elliptic anisotropies in peripheral collisions, which quickly rise with momentum, can only be explained in simulations when assuming a strong momentum dependence of nucleonic mean field. This momentum dependence must strengthen with the rise of density above normal. The meanfield parametrizations, which describe the data in simulations with various success, are confronted with mean fields from microscopic nuclear-matter calculations. Two of the microscopic potentials in the comparisons have unacceptably weak momentum-dependencies at supranormal densities. The optical potentials from the Dirac-Brueckner-Hartree-Fock calculations, on the other hand, together with the UV14 + TNI potential from variational calculations, agree rather well within the region of sensitivity with the parametrized potentials that best describe the data.