Azimuthally anisotropic emission of pions in symmetric heavy-ion collisions

Triple differential cross sections d3 sigma /dp3 for charged pions produced in symmetric heavy-ion collisions were measured with the KaoS magnetic spectrometer at the heavy-ion synchrotron facility SIS at GSI. The correlations between the momentum vectors of charged pions and the reaction plane in 197Au+197Au collisions at an incident energy of 1 GeV/nucleon were determined. We observe, for the first time, an azimuthally anisotropic distribution of pions, with enhanced emission perpendicular to the reaction plane. The anisotropy is most pronounced for pions of high transverse momentum in semicentral collisions

Exclusive measurement of breakup reactions with the one-neutron halo nucleus sup 1 sup 1 Be

Electromagnetic and nuclear inelastic scattering of the halo nucleus sup 1 sup 1 Be have been investigated by a measurement of the one-neutron removal channel, utilizing a secondary sup 1 sup 1 Be beam with an energy of 520 MeV/nucleon impinging on lead and carbon targets. All decay products, i.e. sup 1 sup 0 Be fragments, neutrons, and gamma-rays have been detected in coincidence. Partial cross sections for the population of ground and excited states in sup 1 sup 0 Be were determined for nuclear diffractive breakup as well as for electromagnetically induced breakup. The partial cross sections for ground-state transitions have been differentiated further with respect to excitation energy, and the dipole-strength function associated solely with transitions of the halo 2s sub 1 sub / sub 2 neutron to the continuum has been derived. The extracted dipole strength integrated from the neutron threshold up to 6.1 MeV excitation energy amounts to 0.90(6) e sup 2 fm sup 2. A spectroscopic factor for the nu 2s sub 1 sub / sub 2 x sup 1 sup 0 Be(0 sup +) single-particle configuration of 0.61(5) and a root-mean-square radius of the 2s sub 1 sub / sub 2 neutron wave function of 5.7(4) fm have been deduced

Two-phonon giant resonances in sup 1 sup 3 sup 6 Xe, sup 2 sup 0 sup 8 Pb, and sup 2 sup 3 sup 8 U

The excitation of the double-phonon giant dipole resonance was observed in heavy projectile nuclei impinging on targets of high nuclear charge with energies of 500-700 MeV/nucleon. New experimental data are presented for sup 1 sup 3 sup 6 Xe and sup 2 sup 3 sup 8 U together with further analysis of earlier data on sup 2 sup 0 sup 8 Pb. Differential cross sections d sigma/dE sup * and d sigma/d theta for electromagnetic excitations were deduced. Depending on the isotope, cross sections appear to be enhanced in comparison to those expected from a purely harmonic nuclear dipole response. The cumulative effect of excitations of two-phonon states composed of one dipole and one quadrupole phonon, of predicted anharmoniticies in the double-phonon dipole response, and of damping of the dipole resonance during the collision may account for the discrepancy. In addition, decay properties of two-phonon resonances were studied and compared to that of a statistical decay