Effective Charges Near 56Ni and Production of Anti-Nuclei Studied with Heavy-Ion Reactions

This thesis presents the research performed within two different research groups using heavy-ion induced nuclear reactions. They offer the opportunity to investigate different properties of nuclear matter. The results are based on measurements using a variety of different experimental techniques. The PHENIX experiment measured the production of deuteron and anti-deuterons at mid-rapidity in gold-gold collisions at the Relativistic Heavy-Ion Collider, RHIC. The invariant yields and transverse momentum spectra are presented. The results are not in agreement with a simple coalescence model with a constant coalescence paramete. Excited states of atomic nuclei were populated using fusion-evaporation reactions. The emitted gamma rays were detected in large multi-detector arrays. One experiment was in conjunction with a plunger device. Lifetimes of analogue states in the A=51 mirror nuclei 51Fe and 51Mn were measured using the recoil distance Doppler shift (RDDS) technique. The deduced B(E2) values make possible an investigation of isoscalar and isovector polarization charges. A comparison between the experimental results and large-scale shell-model calculations yields a quantitative estimate of the effective nucleon charges in the fp-shell

Reconstructing breakup at sub-barrier energies

Using a position sensitive detector array, back-angle coincidence measurements of breakup fragments at sub-barrier energies has enabled the complete characterisation of the breakup processes in the reactions of 6,7Li with 208Pb. Breakup processes and the

Two Particle Azimuthal Correlation Measurements in PHENIX

Two particle azimuthal correlation functions are presented for charged hadrons produced in Au-Au collisions at RHIC sqrt(s_NN)=200 GeV.The correlation functions indicate sizeable asymmetries and anisotropies. The trend of the asymmetries is compatible with the presence of emission patterns associated with mini-jets. The magnitude and the trend of the differential anisotropies v_2(p_T) and v_2(N_Part), provide important model constraints.Comment: 4 pages 3 fig

Disentangling effects of nuclear structure in heavy element formation

Forming the same heavy compound nucleus with different isotopes of the projectile and target elements allows nuclear structure effects in the entrance channel (resulting in static deformation) and in the dinuclear system to be disentangled. Using three isotopes of Ti and W, forming 232Cm, with measurement spanning the capture barrier energies, alignment of the heavy prolate deformed nucleus is shown to be the main reason for the broadening of the mass distribution of the quasifission fragments as the beam energy is reduced. The complex, consistently evolving mass-angle correlations that are observed carry more information than the integrated mass or angular distributions, and should severely test models of quasifission

Results on Photon Production in Au+Au Collisions at RHIC

The status of the search for direct photons in Au+Au collisions at sqrt{s_NN} = 130 GeV and sqrt{s_NN} = 200 GeV with the PHENIX experiment is presented. Within errors, no excess of direct photons was found in a first analysis pass done on a limited data set. Significantly reduced systematic and statistical uncertainties are expected in future analyses.Comment: 4 pages, 3 figures. Talk presented at the Quark Matter 2002 conference, Nantes, France, July 18-24, 2002. To appear in the proceedings (Nucl. Phys. A

Dynamical approach to fusion-fission process in superheavy mass region

In order to describe heavy-ion fusion reactions around the Coulomb barrier with an actinide target nucleus, we propose a model which combines the coupled-channels approach and a fluctuation-dissipation model for dynamical calculations. This model takes i

Predominant Time Scales in Fission Processes in Reactions of S, Ti and Ni with W: Zeptosecond versus Attosecond

The inhibition of fusion by quasifission is crucial in limiting the formation of superheavy elements in collisions of heavy nuclei. Time scales of ∼10⊃-18s inferred for fissionlike events from recent crystal blocking measurements were interpreted to

Influence of entrance-channel magicity and isospin on quasi-fission

The role of spherical quantum shells in the competition between fusion and quasi-fission is studied for reactions forming heavy elements. Measurements of fission fragment mass distributions for different reactions leading to similar compound nuclei have been made near the fusion barrier. In general, more quasi-fission is observed for reactions with non-magic nuclei. However, the 40Ca+ 208Pb reaction is an exception, showing strong evidence for quasi-fission, though both nuclei are doubly magic. Time-dependent Hartree-Fock calculations predict fast equilibration of N/Z in the two fragments early in the collision. This transfer of nucleons breaks the shell effect, causing this reaction to behave more like a non-magic one in the competition between fusion and quasi-fission. Future measurements of fission in reactions with exotic beams should be able to test this idea with larger N/Z asymmetries

Quasifission and Shell Effects in Reactions Forming 266Sg

The role of shell effects in reactions forming the heavy element 266Sg was investigated using the Mass Angle Distribution technique. For the 34S + 232Th reaction the doubly magic shell closure at 208Pb was found to strongly influence asymmetric quasifiss

Predominance of transfer in triggering breakup in sub-barrier reactions of 6,7Li with 144Sm, 207,208Pb, and 209Bi

Coincidence measurements of breakup fragments were carried out for the 7Li+144Sm and 6,7Li+207,208Pb,209Bi reactions at sub-barrier energies. Breakup modes in reactions of 6,7Li were identified through the reaction Q values, and the time-scales of each p