FRONTIERS IN NUCLEAR STRUCTURE, ASTROPHYSICS, AND REACTIONS  FINUSTAR

The Antiproton‐Ion‐Collider at FAIR
View Description Hide DescriptionAn antiproton‐ion collider (AIC) has been proposed for the FAIR Project at Darmstadt to independently determine rms radii for protons and neutrons in stable and short lived nuclei by means of antiproton annihilation at medium energies. The AIC makes use of the ELISe electron ion collider complex to store, cool and collide antiprotons of 30 MeV energy with short lived radioactive ions in the NESR. The exotic nuclei are produced by projectile fragmentation or projectile fission and separated in the Super FRS. By detecting the loss of stored ions using the Schottky method the total absorption cross‐section for antiprotons on the stored ions with mass A will be measured. Cross sections for the absorption on protons and neutrons, respectively, will be measured by the detection of residual nuclei with A‐1 either by the Schottky method or by detecting them in recoil detectors after the first dipole stage of the NESR following the interaction zone. The absorption cross sections are in first order directly proportional to the mean square radii.

Microscopic nuclear models for nucleosynthesis applications
View Description Hide DescriptionImportant effort has been devoted in the last decades to measure reaction cross sections. Despite such effort, many nuclear applications still require the use of theoretical predictions to estimate experimentally unknown cross sections. Most of the nuclear ingredients in the calculations of reaction cross sections need to be extrapolated in an energy or/and mass domain out of reach of laboratory simulations. In addition, some applications often involve a large number of unstable nuclei, so that only global approaches can be used. For these reasons, when the nuclear ingredients to the reaction models cannot be determined from experimental data, it is highly recommended to consider preferentially microscopic or semi‐microscopic global predictions based on sound and reliable nuclear models which, in turn, can compete with more phenomenological highly‐parametrized models in the reproduction of experimental data. The latest developments and improvements made in the prediction of nuclear structure properties and nuclear level densities within global microscopic models are reviewed.

Photodissociation experiments for p‐process nuclei
View Description Hide DescriptionThe near‐threshold photodissociation of nuclides received an increased attention in recent years due to its relevance for heavy element production in astrophysical scenarios. Therefore, a research program has been started to study photodissociation reactions using energetic bremsstrahlung from the new ELBE electron linear accelerator. Special emphasis was devoted to the neutron deficient nuclei with A≈100 which may have been produced in cosmic high‐temperature regions by (γ,n), (γ,p), or (γ, α)‐reactions. First data were obtained for the astrophysically important target nucleus ^{92} Mo by observing the radioactive decay of the nuclides produced by bremsstrahlung irradiation at end‐point energies between 11.8 and 14.0 MeV. The results are compared to recent statistical‐model calculations.

Cross section measurements of the Big Bang nucleosynthesis reaction D(α,γ)^{6}Li by Coulomb dissociation of ^{6}Li
View Description Hide DescriptionThe possibility that big‐bang nucleosynthesis (BBN) may produce nontrivial amounts of ^{6}Li is under study since the recent observations of this element in old halo stars. However, the interpretation of these observations needs a precise knowledge of the reaction rate of D(α, γ)^{6}Li which, at present, is extremely uncertain (a factor of 20) at the energies of astrophysical interest (E_{ cm } ⩽ 300 keV). This uncertainty originates from difficulties in both theoretical estimates and experimental determinations of the D(α, γ)^{6}Li capture reaction cross section. New measurements of the cross section of D(α, γ)^{6}Li reaction using Coulomb dissociation of ^{6}Li at 150 A MeV have been performed recently at GSI. The results will be compared to previous measurements and theoretical calculations.

NACRE Update and Extension Project
View Description Hide DescriptionNACRE, the ‘nuclear astrophysics compilation of reaction rates’, has been widely utilized in stellar evolution and nucleosynthesis studies since its publication in 1999. We describe here the current status of a Konan‐Université Libre de Bruxelles (ULB) joint project that aims at its update and extension.

Gamma‐ray Spectroscopy of Isobaric Multiplets
View Description Hide DescriptionThe approximate charge symmetry and charge independence of the nuclear force results in striking symmetries in nuclear behavior between isobaric analogue states (IAS) — states of the same isospin quantum number in a set of nuclei of the same total number of nucleons (an isobaric multiplet). The Coulomb force breaks this symmetry and is the dominating factor in producing the large shifts in absolute binding energy between IAS. The recent development of large gamma‐ray spectrometers has resulted in a wealth of information on IAS at high excitation energy and high angular momentum. The very small differences in excitation energy between the IAS can be interpreted, principally, in terms of Coulomb effects. The analysis of these Coulomb differences has been shown to be a remarkably sensitive probe of nuclear structure effects as well as providing stringent tests of state‐of‐the‐art shell‐model calculations. Some specific structural phenomena examined through the study of such energy differences are presented in this review, and include the evolution of nuclear radius/deformation as a function of spin and the electromagnetic spin‐orbit effect.

New Developments in TRIμP and RIASH at KVI
View Description Hide DescriptionThe status of the TRIμP facility at KVI is reviewed. Recent results on ion catcher devices are described. A thermo‐ionizer for use with alkali and earth‐alkali elements is close to completion. Concerning the use of superfluid helium as stopping medium, evidence that second sound pulses can be used to extract ions from the helium surface has been obtained. Based on the observation of highly efficient ion transport in helium, neon and argon gas below about 100 K, we propose the operation of noble gas ion catchers at cryogenic temperatures.

Measurement Of The β‐ν Correlation In ^{6}He Using A Transparent Paul Trap
View Description Hide DescriptionThe angular correlation between the electron and the neutrino in nuclear β‐decay constitutes a sensitive observable to search for the existence of exotic couplings in the weak interaction. In this contribution, we describe the progress of the LPCTrap experiment, devoted to measure the β‐ν angular correlation in the pure Gamow‐Teller (GT) decay of ^{6}He using a transparent Paul trap. We present a first coincidence spectrum, obtained during the commissioning run, which is the first β‐recoil coincidence measurement obtained from any ion trap.

ISOLTRAP Mass Measurements for Weak‐Interaction Studies
View Description Hide DescriptionThe conserved‐vector‐current (CVC) hypothesis of the weak interaction and the unitarity of the Cabibbo‐Kobayashi‐Maskawa (CKM) matrix are two fundamental postulates of the Standard Model. While existing data on CVC supports vector current conservation, the unitarity test of the CKM matrix currently fails by more than two standard deviations. High‐precision mass measurements performed with the ISOLTRAP experiment at ISOLDE/CERN provide crucial input for these fundamental studies by greatly improving our knowledge of the decay energy of super‐allowed β decays. Recent results of mass measurements on the β emitters ^{18}Ne, ^{22} Mg, ^{34}Ar, and ^{74}Rb as pertaining to weak‐interaction studies are presented.

Calculation Of Two Neutrino Double Beta Decay Nuclear Matrix Elements For ^{128,130}Te
View Description Hide DescriptionBased on Pyatov‐Salamov method, spin‐isospin (Gamow‐Teller) effective interaction strength parameter has been found self‐consistently. Then, the problem has been solved within the framework of QRPA. Gamow‐Teller matrix elements for both β^{−} and β^{+} transitions and two neutrino double beta decay nuclear matrix elements have been calculated for ^{128,130}Te→^{128,130}Xe transitions. The obtained results have been compared with the corresponding experimental data and other theoretical results.

Nuclear binding energy at high spin
View Description Hide DescriptionA method to calculate absolute values of the total nuclear binding energy in the high‐spin regime is briefly described. Applications to test the position of specific orbitals are examplified on Z = 36 Kr isotopes with N = 36 – 38. Calculated binding energies of possible configurations for one dipole band in ^{199} Pb are compared with experiment.

Clusterization and quadrupole deformation in nuclei
View Description Hide DescriptionWe study the interrelation of the clusterization and quadrupole deformation of atomic nuclei, by applying cluster models. Both the energetic stability and the exclusion principle is investigated. Special attention is paid to the relative orientations of deformed clusters.

Self‐consistent models for the collective excitation phenomena in exotic nuclei
View Description Hide DescriptionMultipole excitation phenomena in exotic nuclei are investigated within the framework of the fully self‐consistent Relativistic Quasi‐particle Random‐Phase Approximation (RQRPA) based on the Relativistic Hartree‐Bogoliubov (RHB) model with density dependent meson‐nucleon couplings, and finite‐range Gogny interaction to account for the pairing correlations. The RHB+RQRPA study of nuclei towards the proton drip‐line indicates the appearance of an exotic collective excitation mode: the proton pygmy dipole resonance, due to oscillations of loosely bound protons against the rest of nucleons. The continuum RPA using Skyrme interactions is employed in a study of doubly magic ^{48} Ni, resulting in a rather broad distribution of the low‐lying dipole strength, due to the coupling to the continuum.

The One‐Body and Two‐Body Density Matrices of Finite Nuclei and Center‐of‐Mass Correlations
View Description Hide DescriptionA method is presented for the calculation of the one‐body (1DM) and two‐body (2DM) density matrices and their Fourier transforms in momentum space, that is consistent with the requirement for translational invariance (TI), in the case of a nucleus (a finite self‐bound system). We restore TI by using the so‐called fixed center‐of‐mass (CM) approximation for constructing an intrinsic nuclear ground state wavefunction (WF) by starting from a non‐translationally invariant (nTI) WF and applying a projection prescription. We discuss results for the one‐body (OBMD) and two‐body (TBMD) momentum distributions of the ^{4}He nucleus calculated with the Slater determinant of the harmonic oscillator (HO) orbitals, as the initial nTI WF. Effects of such an inclusion of CM correlations are found to be quite important in the momentum distributions.

Chaos and 1/f noise in nuclear spectra
View Description Hide DescriptionMany complex systems in nature and in human society exhibit time fluctuations characterized by a power spectrum S(f) which is a power function of the frequency f. Examples with this behavior are the Sun spot activity, the human heartbeat, the DNA sequence, or Bach’s First Brandenburg Concert. In this work, we show that the energy spectrum fluctuations of quantum systems can be formally considered as a discrete time series, with energy playing the role of time. Because of this analogy, the fluctuations of quantum energy spectra can be studied using traditional methods of time series, like calculating the Fourier transform and studying the power spectrum. We present the results for paradigmatic quantum chaotic systems like atomic nuclei (by means of large scale shell‐model calculations) and the predictions of random matrix theory. We have found a surprising general property of quantum systems: The energy spectra of chaotic quantum systems are characterized by 1/f noise, while regular quantum systems exhibit 1/f ^{2} noise. Some other interesting applications of this time series analogy are a test of the existence of quantum chaos remnants in the nuclear masses, and the study of the order to chaos transition in semiclassical systems. In this case, it is found that the energy level spectrum exhibits 1/f ^{α} noise with the exponent changing smoothly from α = 2 in regular systems to α = 1 in chaotic systems.

Spectroscopy of Moderately Neutron‐rich Nuclei with the CLARA‐PRISMA Setup
View Description Hide DescriptionDeep‐inelastic and multi‐nucleon transfer reactions can be used to populate nuclei with relatively large neutron excess. Recently, at the Laboratori Nazionali di Legnaro, a setup consisting on an efficient γ‐ray detection system CLARA coupled to the large acceptance magnetic spectrometer PRISMA, capable of tracking the trajectories of the reaction products, has been assembled. During the first year of activity, the experiments performed with the CLARA‐PRISMA setup, have been focused mainly on the nuclear structure of neutron‐rich nuclei. In particular, nuclei around N=20, N=50 and lying in the A∼60 transitional region with N<40, have been investigated. In this contribution, results of these experiments will be reported.

First Results from MoNA
View Description Hide DescriptionWe explore the limits of nuclear stability and the consequences on nuclear structure theory by measuring masses of neutron‐unbound nuclei and level energies above the neutron separation energy such as for the first excited state in ^{24}O. Open problems in reaction theory are addressed by, among others, measurements of the Coulomb breakup of ^{8}Li on a Pb and C target at 40 and 70 MeV/u.

Large Amplitude Q_{n}‐Q_{p} Collectivity in Neutron Rich Oxygen Isotopes
View Description Hide DescriptionBy means of HFB with constraints on both neutron and proton quadrupole moments Q̂_{n} and Q̂_{p} , we investigate the large amplitude isovector deformation properties of neutron rich isotopes of Oxygen. We then analyze the collective dynamics in the {〈Q̂_{n} 〉,〈Q̂_{p} 〉} parametrized surface by means of the spin and particle projected Generator Coordinate Method.

Present and Future Experiments with Stored Exotic Nuclei at Relativistic Energies
View Description Hide DescriptionRecent progress is presented from experiments on masses and lifetimes of bare and few‐electron exotic nuclei at GSI. Relativistic rare isotopes produced via projectile fragmentation and fission were separated in flight by the fragment separator FRS and injected into the storage ring ESR. This worldwide unique experimental technique gives access to all fragments with half‐lives down to the microsecond range. The great research potential is also demonstrated by the discovery of new isotopes along with simultaneous measurements of mass and lifetime. Representative results from time‐resolved Schottky mass spectrometry are compared with modern theoretical predictions. The measured isospin dependence of pairing‐gap energies is not reproduced by conventional mass models. The first direct observation of bound‐state beta decay has been achieved. Single particle decay measurements and the continuous recording of both stored mother and daughter nuclei open up a new era for spectroscopy. The combination of stochastic and electron cooling has allowed us to measure with Schottky analysis for the first time short‐lived isomers. The future international NUSTAR facility at FAIR consisting of a new large‐acceptance in‐flight separator (Super‐FRS) will be an ideal tool to study the r‐ and rp‐process nuclei.