Nuclear halo and its scaling laws

We have proposed a procedure to extract the probability for valence particle being out of the binding potential from the measured nuclear asymptotic normalization coefficients. With this procedure, available data regarding the nuclear halo candidates are systematically analyzed and a number of halo nuclei are confirmed. Based on these results we have got a much relaxed condition for nuclear halo occurrence. Furthermore, we have presented the scaling laws for the dimensionless quantity $/R^{2}$ of nuclear halo in terms of the analytical expressions of the expectation value for the operator $r^{2}$ in a finite square-well potential.Comment: 14 pages, 3 figure

The size of two-body weakly bound objects : short versus long range potentials

The variation of the size of two-body objects is investigated, as the separation energy approaches zero, with both long range potentials and short range potentials having a repulsive core. It is shown that long range potentials can also give rise to very extended systems. The asymptotic laws derived for states with angular momentum l=1,2 differ from the ones obtained with short range potentials. The sensitivity of the asymptotic laws on the shape and length of short range potentials defined by two and three parameters is studied. These ideas as well as the transition from the short to the long range regime for the l=0 case are illustrated using the Kratzer potential.Comment: 5 pages, 3 figures, submitted to Physical Review Letter

HIE-ISOLDE: the Scientific Opportunities

The HIE-ISOLDE project aims at substantial improvements of the energy range, the intensity and the quality of the secondary radioactive beams produced at the ISOLDE facility at CERN. This report presents the questions within nuclear physics and related areas, including nuclear astrophysics, Standard Model tests and condensed matter physics, that scientists will be able to address at HIE-ISOLDE and gives specific examples of how the upgrades will improve the experimental conditions. The physics possibilities at HIE-ISOLDE were reviewed at the NuPAC meeting (Nuclear Physics and Astrophysics at CERN) held at CERN in October 2005; this report gives a more comprehensive overview and incorporates technical and scientific developments that have taken place since then

Extended sudden approximation model for high-energy nucleon removal reactions

A model based on the sudden approximation has been developed to describe high energy single nucleon removal reactions. Within this approach, which takes as its starting point the formalism of Hansen \cite{Anne2}, the nucleon-removal cross section and the full 3-dimensional momentum distributions of the core fragments including absorption, diffraction, Coulomb and nuclear-Coulomb interference amplitudes, have been calculated. The Coulomb breakup has been treated to all orders for the dipole interaction. The model has been compared to experimental data for a range of light, neutron-rich psd-shell nuclei. Good agreement was found for both the inclusive cross sections and momentum distributions. In the case of $^{17}$C, comparison is also made with the results of calculations using the transfer-to-the-continuum model. The calculated 3-dimensional momentum distributions exhibit longitudinal and transverse momentum components that are strongly coupled by the reaction for s-wave states, whilst no such effect is apparent for d-waves. Incomplete detection of transverse momenta arising fromlimited experimental acceptances thus leads to a narrowing of the longitudinal distributions for nuclei with significant s-wave valence neutron configurations, as confirmed by the data. Asymmetries in the longitudinal momentum distributions attributed to diffractive dissociation are also explored.Comment: 16 figures, submitted to Phys. Rev.

Halos and related structures

The halo structure originated in nuclear physics but is now encountered more widely. It appears in loosely bound, clustered systems where the spatial extension of the system is significantly larger than that of the binding potentials. A review is given on our current understanding of these structures, with an emphasis on how the structures evolve as more cluster components are added, and on the experimental situation concerning halo states in light nuclei.Comment: 27 pages, 3 figures, Contribution to Nobel Symposium 152 "Physics With Radioactive Beams

New Discrete Basis for Nuclear Structure Studies

A complete discrete set of spherical single-particle wave functions for studies of weakly-bound many-body systems is proposed. The new basis is obtained by means of a local-scale point transformation of the spherical harmonic oscillator wave functions. Unlike the harmonic oscillator states, the new wave functions decay exponentially at large distances. Using the new basis, characteristics of weakly-bound orbitals are analyzed and the ground state properties of some spherical doubly-magic nuclei are studied. The basis of the transformed harmonic oscillator is a significant improvement over the harmonic oscillator basis, especially in studies of exotic nuclei where the coupling to the particle continuum is important.Comment: 13 pages, RevTex, 6 p.s. figures, submitted to Phys. Rev.

Microscopic description of the beta delayed deuteron emission from \bbox{^6}He

The beta delayed deuteron emission from $^6$He is studied in a dynamical microscopic cluster model. This model gives a reasonably good description for all the subsystems of $^6$He and $^6$Li in a coherent way, without any free parameter. The beta decay transition probability to the $^6$Li ground state is underestimated by a few percents. The theoretical beta delayed deuteron spectrum is close to experiment but it is also underestimated by about a factor 1.7. We argue that, in spite of their different magnitudes, both underestimations might have a common origin. The model confirms that the neutron halo part of the $^6$He wave function plays a crucial role in quenching the beta decay toward the $\alpha$ + d channel.Comment: LATEX with REVTEX, Submitted to Phys. Rev. C, 11 pages, 3 figures (not included) are available upon request. ATOMKI-93/

Beta-delayed deuteron emission from 11Li: decay of the halo

The deuteron-emission channel in the beta-decay of the halo-nucleus 11Li was measured at the ISAC facility at TRIUMF by implanting post-accelerated 11Li ions into a segmented silicon detector. The events of interest were identified by correlating the decays of 11Li with those of the daughter nuclei. This method allowed the energy spectrum of the emitted deuterons to be extracted, free from contributions from other channels, and a precise value for the branching ratio B_d = 1.30(13) x 10-4 to be deduced for E(c.m.) > 200 keV. The results provide the first unambiguous experimental evidence that the decay takes place essentially in the halo of 11Li, and that it proceeds mainly to the 9Li + d continuum, opening up a new means to study of the halo wave function of 11Li.Comment: 4 pages, 3 figure

Study of bound states in 12Be through low-energy 11Be(d,p)-transfer reactions

The bound states of 12Be have been studied through a 11Be(d,p)12Be transfer reaction experiment in inverse kinematics. A 2.8 MeV/u beam of 11Be was produced using the REX-ISOLDE facility at CERN. The outgoing protons were detected with the T-REX silicon detector array. The MINIBALL germanium array was used to detect gamma rays from the excited states in 12Be. The gamma-ray detection enabled a clear identification of the four known bound states in 12Be, and each of the states has been studied individually. Differential cross sections over a large angular range have been extracted. Spectroscopic factors for each of the states have been determined from DWBA calculations and have been compared to previous experimental and theoretical results

Nuclear Skins and Halos in the Mean-Field Theory

Nuclei with large neutron-to-proton ratios have neutron skins, which manifest themselves in an excess of neutrons at distances greater than the radius of the proton distribution. In addition, some drip-line nuclei develop very extended halo structures. The neutron halo is a threshold effect; it appears when the valence neutrons occupy weakly bound orbits. In this study, nuclear skins and halos are analyzed within the self-consistent Skyrme-Hartree-Fock-Bogoliubov and relativistic Hartree-Bogoliubov theories for spherical shapes. It is demonstrated that skins, halos, and surface thickness can be analyzed in a model-independent way in terms of nucleonic density form factors. Such an analysis allows for defining a quantitative measure of the halo size. The systematic behavior of skins, halos, and surface thickness in even-even nuclei is discussed.Comment: 22 RevTeX pages, 22 EPS figures included, submitted to Physical Review