Evidence for excitation of exotic $S=+1$ pentaquark degrees of freedom is presented by studying optical-potential fits to $K^{+}$-nucleus total, reaction and elastic-differential cross section data at $p_{\mathrm{lab}}~500\text{−}700$ MeV/c. Estimates of the underlying two-nucleon absorption $K^{+}\mathit{nN}\to {\Theta }^{+}N$ reaction cross section are made and are used for discussing the anticipated cross section of the strangeness exchange reaction $K^{+}N\to \pi {\Theta }^{+}$.

The neutron capture cross sections of ${}^{175}\mathrm{Lu}$ and ${}^{176}\mathrm{Lu}$ have been measured in the energy range 3–225 keV at the Karlsruhe 3.7 MV Van de Graaff accelerator. Neutrons were produced via the ${}^7\mathrm{Li}$($p,n$)${}^7\mathrm{Be}$ reaction by bombarding metallic Li targets with a pulsed proton beam, and capture events were registered with the Karlsruhe 4π barium fluoride detector. The cross sections were determined relative to the gold standard using isotopically enriched as well as natural lutetium oxide samples. Overall uncertainties of ∼1% could be achieved in the final cross section ratios to the gold standard, about a factor of 5 smaller than in previous works. Maxwellian averaged neutron capture cross sections were calculated for thermal energies between kT = 8 and 100 keV. These values are systematically larger by ∼7% than those reported in recent evaluations. These results are of crucial importance for the assessment of the s-process branchings at A = 175/176.

Angular distribution measurements of ${}^2\mathrm{H}$(${}^7\mathrm{Be}$,${}^7\mathrm{Be}$)${}^2\mathrm{H}$ and ${}^2\mathrm{H}$(${}^7\mathrm{Be}$,${}^8\mathrm{B}$)n reactions at $E_{c.m.}~4.5$ MeV were performed to extract the astrophysical $S_{17}(0)$ factor using the asymptotic normalization coefficient (ANC) method. For this purpose a pure, low emittance ${}^7\mathrm{Be}$ beam was separated from the primary ${}^7\mathrm{Li}$ beam by a recoil mass spectrometer operated in a novel mode. A beam stopper at 0° allowed for the use of a higher ${}^7\mathrm{Be}$ beam intensity. Measurement of the elastic scattering in the entrance channel using kinematic coincidence, facilitated the determination of the optical model parameters needed for the analysis of the transfer data. The present measurement significantly reduces errors in the extracted ${}^7\mathrm{Be}$($p,\gamma$) cross section using the ANC method. We get $S_{17}$ (0) = 20.7 ± 2.4 eV b.

In this report we study the origin of spin-zero ground-state dominance for even-even nuclei in the presence of random two-body interactions. We evaluate the ground-state energy in terms of the energy centroid and the width of the random Hamiltonian. For both fermions and bosons in a single orbital, we obtain excellent agreement between the spin-I ground state probabilities predicted by using our formula and those obtained by diagonalizing the random Hamiltonian.

The relativistic microscopic optical potential (RMOP) is studied within the framework of the Dirac-Brueckner-Hartree-Fock (DBHF) approach. A new decomposition of the Dirac structure of nuclear self-energy in the DBHF is extended to asymmetric nuclear matter calculations. A nucleon effective interaction is introduced to reproduce the results of the G matrix. The real part of nucleon self-energy in asymmetric nuclear matter is calculated with the G matrix in the Hartree-Fock approach, while the imaginary part is obtained from the polarization diagram. Nuclear optical potentials in finite nuclei are derived from the self-energies in asymmetric matter through a local-density approximation. The differential cross sections and the analyzing powers in $p+$${}^{40}\mathrm{Ca}$ and $p+$${}^{208}\mathrm{Pb}$ elastic scattering at $E_p\le 200$ MeV are studied with these RMOPs. A satisfactory agreement with the experimental data is found. This is achieved without readjusting phenomenologically the RMOP derived from the DBHF plus polarization diagram.

We present a first exploratory study for hyperon-nucleon interactions using renormalization group techniques. The effective two-body low-momentum potential $V_{\text{low}k}$ is obtained by integrating out the high-momentum components from realistic Nijmegen YN potentials. A T-matrix equivalence approach is employed, so that the low-energy phase shifts are reproduced by $V_{\text{low}k}$ up to a momentum scale $\Lambda ~500$ MeV. Although the various bare Nijmegen models differ somewhat from each other, the corresponding $V_{\text{low}k}$ interactions show convergence in some channels, suggesting a possible model-independent YN interaction at low momenta.

In a γ-ray spectroscopy experiment with the $(K^{-},{\pi }^{-})$ reaction on a ${}^{10}\mathrm{B}$ target, we have observed the $7/2^{+}\to 5/2^{+}$ spin-flip $M1$ transition in ${}_{\Lambda }^7\text{Li}$ via γ-γ coincidence with the $5/2^{+}\to 1/2^{+}E2$ transition. This is the first successful $\gamma \text{−}\gamma$ coincidence measurement for hypernuclei. The measured $M1\hspace{1em}\gamma$-ray energy is $470.8\pm 1.9$(stat)$\pm 0.6$(syst) keV. The spacing of the $7/2^{+},5/2^{+}$ doublet is consistently explained using the strengths of the spin-spin, Λ-spin-orbit, and tensor interactions obtained from previous γ-spectroscopy experiments.

We analyze α decays to rotational states in even-even nuclei by using the stationary coupled channels approach. Collective excitations are described by the rigid rotator model. The α-nucleus interaction is given by a double folding procedure using M3Y plus Coulomb nucleon-nucleon forces. We use a harmonic oscillator repulsive potential with one independent parameter, to simulate the Pauli principle. The decaying state is identified with the first resonance inside the resulting pocketlike potential. The energy of the resonant state is adjusted to the experimental Q value by using the depth of the repulsion. We obtained a good agreement with existing experimental data concerning total half-lives and decay widths to $J=2^{+}$ states by changing the factor multiplying the nucleon-nucleon interaction according to the rule $v_a=0.668-0.004\hspace{1em}(A-208)$. Concerning the decay widths to $J=4^{+}$ states we obtained a good agreement for $Z=90$ neutron chain and a satisfactory description for $Z=92,96$, and 98, chains. It is possible to improve the agreement concerning transitions to $J=4^{+}$ states by considering a constant quenching strength $v_a=0.6$ and by changing the width of the Gaussian describing the α-cluster density according to the rule $b=1.744-0.032\hspace{1em}(A-208)$. We found out that the computed widths to excited states are correlated with the corresponding deformation parameters. We conclude that the α-decay fine structure is a sensitive tool to probe fundamental aspects of the effective nuclear interaction and its dependence on the α clustering.

$B(E3;0_1^{+}\to 3_1^{-})$ transition matrix elements have been measured for even-mass ${}^{124-134}\mathrm{Xe}$ nuclei using subbarrier Coulomb excitation in inverse kinematics. The trends in energy $E(3^{-})$ and $B(E3;0_1^{+}\to 3_1^{-})$ excitation strengths are well reproduced using phenomenological models based on a strong coupling picture with a soft quadrupole mode and an increasing occupation of the intruder $h_{11/2}$ orbital.

The recent discovery of hindrance in heavy-ion induced fusion reactions at extreme sub-barrier energies represents a challenge for theoretical models. Previously, it has been shown that in medium-heavy systems, the onset of fusion hindrance depends strongly on the “stiffness” of the nuclei in the entrance channel. In this work, we explore its dependence on the total mass and the Q-value of the fusing systems and find that the fusion hindrance depends in a systematic way on the entrance channel properties over a wide range of systems.

The anisotropic flow of charged hadrons in asymmetric $\text{Cu}+\text{Au}$ collisions at the Relativistic Heavy Ion Collider is studied in a multiphase transport model. Compared with previous results for symmetric $\text{Au}+\text{Au}$ collisions, charged hadrons produced around midrapidity in asymmetric collisions are found to have a stronger directed flow $v_1$ and their elliptic flow $v_2$ is also more sensitive to the parton scattering cross section. Although higher order flows $v_3$ and $v_4$ are small at all rapidities, both $v_1$ and $v_2$ in these collisions are appreciable and show an asymmetry in forward and backward rapidities.

The conclusions extracted from a recent study of the excitation of giant dipole resonances in nuclei at relativistic bombarding energies open the way for a further simplification of the problem. It consists in the elimination of the relativistic scalar and vector electromagnetic potentials and the familiar numerical difficulties associated with their presence in the calculation scheme. The inherent advantage of a reformulation of the problem of relativistic Coulomb excitation of giant dipole resonances along these lines is discussed.

An exclusive measurement of the Coulomb breakup of ${}^8\mathrm{B}$ into ${}^7\mathrm{Be}$$+p$ at 254A MeV was used to infer the low-energy ${}^7\mathrm{Be}$($p,\gamma$)${}^8\mathrm{B}$ cross section. The radioactive ${}^8\mathrm{B}$ beam was produced by projectile fragmentation of 350A MeV ${}^{12}\mathrm{C}$ and separated with the FRagment Separator (FRS) at Gesellschaft für Schwerionenforschung in Darmstadt, Germany. The Coulomb-breakup products were momentum-analyzed in the KaoS magnetic spectrometer; particular emphasis was placed on the angular correlations of the breakup particles. These correlations demonstrate clearly that $E1$ multipolarity dominates within the angular cuts selected for the analysis. The deduced astrophysical $S_{17}$ factors exhibit good agreement with the most recent direct ${}^7\mathrm{Be}$($p,\gamma$)${}^8\mathrm{B}$ measurements. By using the energy dependence of $S_{17}$ according to the recently refined cluster model for ${}^8\mathrm{B}$ of P. Descouvemont [Phys. Rev. C 70, 065802 (2004)], we extract a zero-energy S factor of $S_{17}(0)=20.6\pm 0.8(\mathrm{stat})\pm 1.2(\mathrm{syst})$ eV b. These errors do not include the uncertainty of the theoretical model to extrapolate to zero relative energy, estimated by Descouvemont to be about 5%.

We implement a cutoff-independent regularization of four-fermion interactions to calculate the color-superconducting gap parameter in quark matter. The traditional cutoff regularization has difficulties for chemical potentials μ of the order of the cutoff Λ, predicting in particular a vanishing gap at $\mu ~\Lambda$. The proposed cutoff-independent regularization predicts a finite gap at high densities and indicates a smooth matching with the weak coupling QCD prediction for the gap at asymptotically high densities.

A complete realistic study of the ${}_{\Lambda }^5\text{He}$ hypernucleus is presented using a realistic Hamiltonian and a fully correlated wave function that takes into account all relevant dynamical correlations and $\Lambda N$ space-exchange correlation (SEC). Results are sensitive to SEC, which significantly affects energy breakdown, Λ-separation energy, nuclear core polarization, point proton radius, and density profiles.

We analyze an exactly solvable many-level pairing model (the picket-fence model) in a boson formalism. By making use of a Marumori-type mapping procedure, we construct a boson image of the model Hamiltonian. Only two- and four-boson operators are included in the boson expansion. We show that the physical spectrum of this Hamiltonian coincides with the exact one, and, in particular, we recover Richardson's equations. We apply this boson formalism to search for possible extensions of the random-phase approximation (RPA). We construct renormalized RPA-type equations in correspondence with different expansions of the boson operators. We discuss two extensions of the RPA and test them by comparing their predictions with the exact results and with those obtained within the RPA and the self-consistent RPA.

Combining analytical and numerical methods, we investigate properties of the two-body random ensemble (TBRE). We compare the TBRE with the Gaussian orthogonal ensemble of random matrices. Using the geometric properties of the nuclear shell model, we discuss the information content of nuclear spectra and gain insight in the difficulties encountered when fitting the effective interaction. We exhibit the existence of correlations between spectral widths pertaining to different quantum numbers. Using these results, we deduce the preponderance of zero-spin ground states in the TBRE. We demonstrate the existence of correlations between spectra with different quantum numbers and/or in different nuclei.

In the cranked Nilsson model plus random phase approximation, we study shape transitions in fast rotating nuclei undergoing backbending, more specifically, ${}^{156}\mathrm{Dy}$ and ${}^{162}\mathrm{Yb}$. We find that backbending in ${}^{156}\mathrm{Dy}$ is correlated with the disappearance of the collective, positive signature γ-vibrational mode in the rotating frame, and a shape transition (axial→ nonaxial) is accompanied by a large acquisition of the γ deformation. We show that such a shape transition can be considered as a phase transition of the first order. In ${}^{162}\mathrm{Yb}$, the quasiparticle alignment dominates the backbending, and the shape transition (axial→ nonaxial) is accompanied by a smooth transition from zero to nonzero values of the γ deformation. We extend the classical Landau theory for rotating nuclei and show that backbending in ${}^{162}\mathrm{Yb}$ is identified with the second-order phase transition. A description of spectral and decay properties of the yrast states and low-lying excitations demonstrates good agreement between our results and experimental data.

A Skyrme-like effective interaction is built up from the equation of state of nuclear matter. The latter is calculated in the framework of the Brueckner-Hartree-Fock approximation with two- and three-body forces. A complete Skyrme parametrization requires a fit of the neutron and proton effective masses and the Landau parameters. The new parametrization is probed on the properties of a set of closed-shell and closed-subshell nuclei, including binding energies and charge radii.