Ultra peripheral heavy ion collisions and the energy dependence of the nuclear radius

To estimate realistic cross sections in ultra peripheral heavy ion collisions we must remove effects of strong absorption. One method to eliminate these effects make use of a Glauber model calculation, where the nucleon-nucleon energy dependent cross sections at small impact parameter are suppressed. In another method we impose a geometrical cut on the minimal impact parameter of the nuclear collision ((b)min > R-1 + R-2, where R-i is the radius of ion 'i'). In this last case the effect of a possible nuclear radius dependence with the energy has not been considered in detail up to now. Here we introduce this effect showing that for final states with small invariant mass the effect is negligible. However when the final state has a relatively large invariant mass, e.g., an intermediate mass Higgs boson, the cross section can decrease up to 50%. (C) 2003 Published by Elsevier B.V.

Nonlocal description of the nuclear interaction

Extensive systematizations of theoretical and experimental nuclear densities and of optical potential strengths extracted from heavy-ion elastic scattering data analyses at low and intermediate energies are presented. The energy-dependence of the nuclear potential is accounted for within a model based on the nonlocal nature of the interaction. The systematics indicates that the heavy-ion nuclear potential can be described in a simple global way through a double-folding shape, which basically depends only on the density of nucleons of the partners in the collision. The possibility of extracting information about the nucleon-nucleon interaction from the heavy-ion potential is investigated.

Collision of positronium with atoms, molecules and ions using a modified coupled-channel framework

Scattering of positronium (Ps) from atoms (H, He, Ne, Ar), molecule (H(2)) and ion (He(+)) have been investigated using a coupled-channel (CC) formalism with a regularised non-local exchange potential. The advantage of using such a regularized exchange potential in the close-coupling formalism and the normalizability aspect of the solution at low energies with a minimum effective coupling are discussed. Results for the elastic and total scattering cross-sections, resonance and binding energies in Ps-H, and pick-off annihilation results in Ps-He are found to be in excellent agreement with measurements and variational predictions. (C) 2000 Elsevier B.V. B.V. All rights reserved.