Impact-parameter dependence of giant resonance excitations in relativistic heavy-ion collisions

Angular distributions of Xe fragments produced in peripheral collisions of a "1"3"6Xe beam (700 MeV/nucleon) with "2"0"8Pb and "n"a"tSn targets were measured. Equivalent sharp-cutoff minimum impact parameters were derived on the basis of a semi-classical description for the electromagnetic excitation of one-and two-phonon giant resonances. The results are compared with current standard parametrizations of minimum impact parameters and with the soft-spheres model using realistic mass density distributions for projectile and targets. (orig.)15 refs.Available from TIB Hannover: RO 801(99-32) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman

Excitation and decay of two-phonon giant dipole resonances

In heavy ion collisions at near relativistic energies, electromagnetic excitation of the double giant dipole resonance occurs with large cross sections. We summarize the presently available experimental data and discuss related theoretical efforts. Emphasis is paid to the question of anharmonicities and to the damping of the two-phonon states. (orig.)Available from TIB Hannover: RO 801(98-60) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman

Large spin alignment of the unbound "5He fragment after fragmentation of 240 MeV/u"6He

Peripheral fragmentation of a 240 MeV/u beam of the halo nucleus "6He incident on carbon target has been studied in a kinematically complete experiment. It is found that one-neutron stripping to the unbound nucleus "5He is the dominant fragmentation mechanism and that it leads to a spin alignment of "5He in a plane perpendicular to the "5He momentum vector. This is expected to be a common feature for all neutron halo nuclei. (orig.)Available from FIZ Karlsruhe / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman

A large area scintillating fiber detector for relativistic heavy ions

A scintillating fiber detector for relativistic heavy ions with an active area of 50 x 50 cm"2 has been developed and was tested with various ion beams (1#<=#Z#<=#92). A count rates of up to 10"5 particles/s, the position resolution was found to be determined by the fiber width of 1 mm; depending on the nuclear charge of the beam, efficiencies between 89% and 100% and time resolutions between 800 and 200 ps (FWHM) were obtained. (orig.)SIGLEAvailable from TIB Hannover: RO 801(97-60) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDEGerman

Invariant mass spectrum and #alpha# - n correlation function studied in the fragmentation of "6He on a carbon target

Momentum distributions and invariant mass spectra from the breakup of "6He ions with an energy of 250 MeV/u interacting with a carbon target have been studied. The data were used to extract information about the reaction mechanism which is influenced by the structure of "6He. It is found that the dominant reaction mechanism is a two-step process: knock out of one neutron followed by the decay of the "5He resonance. The shape of the (#alpha#+n) two-body invariant mass spectrum is interpreted as mainly reflecting the "5He ground state which is a J "#pi# =3/2"- resonance. However, no evidence for correlations between #alpha# particles and neutrons is observed in the momentum widths of the distributions. It is demonstrated that a combined analysis of the two-body invariant mass spectrum and an appropriate correlation function may be used to determine the properties of the intermediate resonance. (orig.)Available from TIB Hannover: RO 801(97-61) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman