Nonmesonic decay of kaonic nuclei is investigated under a $\Lambda (1405)$ doorway picture in which the $\overline{K}$ absorptions in nuclei take place through the $\Lambda (1405)$ resonance. Calculating $\Lambda (1405)N\to \mathit{YN}$ transitions with one-meson exchange, we find that the nonmesonic decay ratio ${\Gamma }_{\Lambda N}/{\Gamma }_{{\Sigma }^{0}N}$ depends strongly on the ratio of the couplings $\Lambda (1405)\text{−}\overline{K}N$ and $\Lambda (1405)\text{−}\pi \Sigma$. Especially, a larger $\Lambda (1405)\text{−}\overline{K}N$ coupling leads to enhancement of the decay to $\Lambda N$. Using the chiral unitary approach for description of the $\overline{K}N$ amplitudes, we obtain ${\Gamma }_{\Lambda N}/{\Gamma }_{{\Sigma }^{0}N}\approx 1.2$ almost independently of the nucleon density and find the total nonmesonic decay width calculated in uniform nuclear matter to be 22 MeV at the normal density.

The angular distributions of $\gamma$ rays and $\alpha$ particles from oriented ${}^{250}\mathrm{Bk}$, ${}^{253,254}\mathrm{Es}$, and ${}^{255}\mathrm{Fm}$ nuclei were investigated to extract hyperfine interaction information for these actinide impurities in an iron host lattice. The hyperfine field of einsteinium in iron was found to be $|B_{\mathit{hf}}(\mathrm{Es}\underline{\mathrm{Fe}}|)=396(32)$ T. With this value the magnetic moment of ${}^{254}\mathrm{Es}$ was then determined as $\left|\mu \right|=4.35(41)\hspace{0.5em}{\mu }_N$.

The low lying states in ${}^{128}\mathrm{Ba}$ have been investigated for the first time with the ${}^{130}\mathrm{Ba}(p,t){}^{128}\mathrm{Ba}$ reaction. The experiment was performed at the Munich Q3D magnetic spectrograph with a 25-MeV proton beam and a high-resolution, 1.5-m-long focal plane detector. As a result of this experiment 27 excited levels with energies below 3.7 MeV have been observed for the first time, significantly increasing (by $~50\%$) the number of levels observed in ${}^{128}\mathrm{Ba}$. Angular distributions of tritons were measured and their comparison with the distorted wave Born approximation calculation allowed in most cases spin and parity assignments for the nuclear levels. The experimental two-neutron transition strengths with transferred angular momentum $L=0$ and 2 are compared with the predictions of the IBA-1 model with a new set of parameters. The results indicate for the first time from a hadronic probe perspective a transitional structure close to the O(6) symmetry for the ${}^{128}\mathrm{Ba}$ nucleus, confirming previous conclusions of $\gamma$-ray spectroscopy studies.

We introduce an iterative importance truncation scheme that aims at reducing the dimension of the model space of configuration interaction approaches by an a priori selection of the physically most relevant basis states. Using an importance measure derived from multiconfigurational perturbation theory in combination with an importance threshold, we construct a model space optimized for the description of individual eigenstates of a given Hamiltonian. We discuss in detail various technical aspects and refinements of the importance truncation, such as perturbative corrections for excluded basis states, threshold extrapolation techniques, and different iterative model-space update schemes. We apply the idea of the importance truncation in the context of the no-core shell model (NCSM) for the ab initio description of nuclear ground states. In a series of benchmark calculations for closed- and open-shell nuclei up to ${}^{16}\mathrm{O}$, we compare the ground-state energies obtained in the importance truncated NCSM to the full NCSM. All calculations show an excellent agreement of importance truncated and full NCSM for all cases where the latter is feasible. The results demonstrate that the importance truncated NCSM, while preserving most of the advantages of the full NCSM, gives access to much larger $N_{\max }\hslash \Omega$ spaces and heavier nuclei. In this way we are able to perform importance truncated NCSM calculations for nuclei such as ${}^{12}\mathrm{C}$ and ${}^{16}\mathrm{O}$ up to $N_{\max }=22$.

We exploit a model describing the breakup of weakly bound nuclei that can be used as a laboratory for testing different prescriptions that have been advanced in the literature to take into account the nearby presence of continuum states. In the model, we follow the evolution of a single-particle wave function in one dimension, initially bound by a Woods-Saxon type potential and then perturbed by a time- and position-dependent external field. Proper choices of this potential can simulate the effect of the interaction between reaction partners in a nuclear collision. These processes generate inelastic excitation probabilities that—distributed over the bound and continuum states of the system—lead to either a partial or a total fragmentation of the final wave function.

The longitudinal momentum distributions of the cross sections of heavy projectile-like residues after fast, direct two-like-nucleon knockout reactions are discussed. Both the two-nucleon inelastic breakup (stripping) and the stripping-diffraction removal events are considered. We show that, because the two mechanisms have a very similar nuclear surface localization, they generate essentially identical longitudinal momentum distributions. The approach used combines reaction dynamics, using the sudden, eikonal and spectator-core approximations, with structure wave functions from the many-body shell model. The sensitivities of the resulting longitudinal momentum distributions to the orbital angular momenta, the separation energies, and the angular momentum coupling of the two removed nucleons are clarified. In particular, the widths of these distributions are shown to provide a very clear signal of the total angular momentum of the removed-nucleon pair—pairs coupled to larger total angular momentum giving broader distributions. These now complete distributions, from correlated wave functions, are significantly different from earlier uncorrelated estimates. Confirmation of these theoretical expectations is presented, based on very recent intermediate-energy, residue final-state inclusive and exclusive two-nucleon removal measurements.

Characteristic signatures of statistical Coulomb fragmentation of highly excited nuclear systems are analyzed. It is found that in many important aspects, they coincide with perceived signatures of phase transitions in confined hypothetical pseudomicrocanonical systems and, therefore, may give rise to an incorrect interpretation of certain experimental observations in terms of phase transitions occurring in nuclear matter. It is demonstrated that domains of negative heat capacity predicted by certain classes of pseudomicrocanonical model calculations for the immediate vicinity of phase transitions are artifacts of an unphysical truncation of the model phase space and that such domains disappear already with a very rudimentary enhancement of this phase space. Appearance of bimodality and of signatures of critical phenomena in Coulomb fragmentation is discussed.

We present a microscopic calculation of the ${}^6\mathrm{He}\hspace{0.5em}\beta$-decay into the ground state of ${}^6\mathrm{Li}$. To this end, we use chiral perturbation theory at next-to-next-to-next-to-leading order to describe the nuclear weak-currents. The nuclear wave functions are derived from the $J$-matrix inverse scattering nucleon-nucleon potential (JISP), and the Schrödinger equation is solved using the hyperspherical-harmonics expansion. Our calculation brings the theoretical decay-rate within $3\%$ of the measured one. This success is attributed to the use of chiral perturbation theory based mesonic currents, whose contribution is qualitatively different compared to the standard nuclear physics approach, where the use of meson exchange currents worsens the comparison to experiment. The inherent inconsistency in the use of the JISP potential together with chiral perturbation theory based is argued not to affect this conclusion, though a more detailed investigation is called for. We conclude that any suppression of the axial constant in nuclear matter is included in this description of the weak interaction in the nucleus.

The cross sections of the ${}^3\mathrm{He}(\alpha ,\alpha ){}^3\mathrm{He}$ and ${}^3\mathrm{He}(\alpha ,\gamma ){}^7\mathrm{Be}$ reactions are studied at low energies using a simple two-body model in combination with a double-folding potential. At very low energies the capture cross section is dominated by direct $s$-wave capture. However, at energies of several MeV the $d$-wave contribution increases, and the theoretical capture cross section depends sensitively on the strength of the $L=2$ potential. Whereas the description of the $L=2$ elastic phase shift requires a relatively weak potential strength, recently measured capture data can be described only with a significantly enhanced $L=2$ potential. A simultaneous description of the new experimental capture data and the elastic phase shifts is not possible within this model. Because of the dominating extranuclear capture, this conclusion holds in general for most theoretical models.

The elastic scattering of the halo nucleus ${}^6\mathrm{He}$ from heavy targets at incident energies near the Coulomb barrier displays a marked deviation from the standard Fresnel-type diffraction behavior. This deviation is due to the strong Coulomb dipole breakup coupling produced by the Coulomb field of the heavy target, a specific feature of the nuclear structure of ${}^6\mathrm{He}$. We have performed Continuum Discretized Coupled Channels calculations for the elastic scattering of ${}^6\mathrm{He}$ and ${}^6\mathrm{Li}$ from ${}^{58}\mathrm{Ni}$, ${}^{120}\mathrm{Sn}$, ${}^{144}\mathrm{Sm}$, ${}^{181}\mathrm{Ta}$ and ${}^{208}\mathrm{Pb}$ targets in order to determine the range of $Z_{\mathrm{T}}$ where this nuclear-structure specific coupling effect becomes manifest. We find that the strong Coulomb dipole breakup coupling effect is only clearly experimentally distinguishable for targets of $Z_{\mathrm{T}}\approx 80$.

The nuclear modification factor $R_{\mathit{AA}}$ of nonphotonic electrons in $\mathrm{Au}+\mathrm{Au}$ collisions at $\sqrt{s_{\mathit{NN}}}=200$ GeV is studied by considering the decays of heavy-flavor hadrons produced in a quark coalescence model. Although an enhanced ${\Lambda }_c/D^0$ ratio is predicted by the coalescence model, it is peaked at small transverse momenta ($~2$ GeV) due to the large difference between heavy and light quark masses. As a result, the enhanced ${\Lambda }_c/D^0$ ratio, which is expected to suppress the electron $R_{\mathit{AA}}$ as the branching ratio of ${\Lambda }_c$ decay into electrons is smaller than that of $D^0$, does not lead to additional suppression of the electron $R_{\mathit{AA}}$ at large transverse momenta ($⩾5$ GeV), where the suppression is mainly due to heavy quark energy loss in produced quark-gluon plasma. Also, the enhanced ${\Lambda }_b/{\overline{B}}^0$ ratio predicted by the coalescence model has even smaller effect on the nonphotonic electron $R_{\mathit{AA}}$ as bottom baryons and mesons have similar branching ratios for semileptonic decays into electrons.

High spin states of ${}^{144}\mathrm{Dy}$ have been studied through in-beam $\gamma$-ray spectroscopy by using the reaction ${}^{92}\mathrm{Mo}({}^{56}\mathrm{Fe},2p2n)$. It has been found that the continuation of the ground-state band forks into three $\Delta I=2$ bands above the $8^{+}$ state. This forking has been attributed to the alignments of $\pi h_{11/2}^2$ or $\nu h_{11/2}^{-2}$ configurations with the help of the systematics in neighboring nuclei. Additionally a negative-parity sideband of $\Delta I=2$ cascades has been observed to start from the $5^{(-)}$ state and continue to a dipole band above the (${13}^{-}$) state through another negative-parity sideband of $\Delta I=2$ cascades in between. These structures have been discussed from the viewpoint of a competition between “Magnetic Rotation” and “Anti-magnetic Rotation” based on a classical particles-plus-rotor model.

The influence of Pauli-blocking medium effects on intermediate-energy one-nucleon removal cross sections for $\mathit{sd}$-shell nuclei have been investigated using density-dependent nucleon-nucleon interaction cross sections within the $S$-matrix formalism under the Glauber approximation. All considered prescriptions for the density dependence result in a reduction of the one-nucleon removal cross sections. The effect is smaller than 20% for incident energies between 50 and 100 MeV/nucleon, and smaller than a few percent above 200 MeV/nucleon.

We aim to study the participant-spectator matter over a wide range of energies of vanishing flow and masses. For this, we have employed different model parameters at central and semicentral colliding geometries. A nearly mass independent nature of the participant matter has been obtained at the energy of vanishing flow. Further, participant matter can also act as an indicator to study the degree of thermalization.

Fusion data for ${}^{48}\mathrm{Ca}+{}^{96}\mathrm{Zr}$ are analyzed by coupled-channels calculations. Puzzling features of a previous analysis are eliminated by applying a potential that has a shallow pocket in the entrance channel. Thus the observed $S$ factor for fusion, which develops a maximum at low energy, can be reproduced fairly well. The high-energy data can also be accounted for but that requires the use of a weak, short-ranged imaginary potential that absorbs the incoming flux near the location of the minimum of the potential pocket. Predictions of the fusion hindrance in other $\mathrm{Ca}+\mathrm{Zr}$ systems are made and are compared with the systematics that has been developed previously.

Anisotropic transverse flow patterns that are observed in relativistic heavy ion collisions can be added to the available microscopic Monte Carlo event generators as a final state modification to the azimuthal angles of the particles, which are generated isotropically. The method proposed for this purpose by A. M. Poskanzer and S. A. Voloshin [Phys. Rev. C 58, 1671 (1998)] is valid only for small values of the Fourier coefficients $v_n$ and therefore it is not suitable for simulations with large values of anisotropy such as the ones predicted for Pb-Pb collisions at the LHC. We present here a possible solution to treat the cases of large anisotropies.

Using molecular dynamics simulations, we determine the structure of neutron star crust made of rapid proton capture nucleosynthesis material. We find a regular body-centered cubic lattice, even with the large number of impurities that are present. Low-charge-$Z$ impurities tend to occupy interstitial positions, while high-$Z$ impurities tend to occupy substitutional lattice sites. We find strong attractive correlations between low-$Z$ impurities that could significantly increase the rate of pycnonuclear (density driven) nuclear reactions. The thermal conductivity is significantly reduced by electron impurity scattering. Our results will be used in future work to study the effects of impurities on mechanical properties such as the shear modulus and breaking strain.

Detailed $\alpha$-decay studies of the neutron-deficient isotope ${}^{194}\mathrm{At}$ have been performed in the complete fusion reaction ${}^{56}\mathrm{Fe}+{}^{141}\mathrm{Pr}\to {}^{194}\mathrm{At}+3n$ at the velocity filter SHIP. Two $\alpha$-decaying isomeric states with half-lives of $T_{1/2}({}^{194}\mathrm{At}{}^{m1})=310(8)$ ms and $T_{1/2}({}^{194}\mathrm{At}{}^{m2})=253(10)$ ms were identified in this nucleus. Their complex decays to the states in the daughter nucleus ${}^{190}\mathrm{Bi}$ are discussed in the article. We propose that similar to the case of the neighboring ${}^{191,192,193,195}\mathrm{At}$ isotopes, the oblate-deformed configurations based on the proton ${1/2}^{+}[440]$ and/or $7/2{}^{-}[514]$ Nilsson orbitals become important in ${}^{194}\mathrm{At}$. A new isomeric state with the half-life of 175(8) ns was observed in ${}^{190}\mathrm{Bi}$.

The role of deformations and orientations of nuclei is studied for the first time in cluster decays of various radioactive nuclei, particularly those decaying to doubly closed shell, spherical ${}^{208}\mathrm{Pb}$ daughter nucleus. Also, the significance of using the correct $Q$-value of the decay process is pointed out. The model used is the preformed cluster model (PCM) of Gupta and collaborators [R. K. Gupta et al., Proc. Int. Conf. on Nuclear Reactions Mechanisms, Varenna, 1988, p. 416; Phys. Rev. C 39, 1992 (1989); 55, 218 (1997); Heavy Elements and Related New Phenomena, edited by W. Greiner and R. K. Gupta, World Sc. 1999, Vol. II, p. 731]. In this model, cluster emission is treated as a tunneling of the confining interaction barrier by a cluster considered already preformed with a relative probability $P_0$. Since both the scattering potential and potential energy surface due to the fragmentation process in the ground state of the parent nucleus change significantly with the inclusion of deformation and orientation effects, both the penetrability $P$ and preformation probability $P_0$ of clusters change accordingly. The calculated decay half-lives for all the cluster decays investigated here are generally in good agreement with measured values for the calculation performed with quadrupole deformations ${\beta }_2$ alone and “optimum” orientations of cold elongated configurations. In some cases, particularly for ${}^{14}\mathrm{C}$ decay of Ra nuclei, the inclusion of multipole deformations up to hexadecapole ${\beta }_4$ is found to be essential for a comparison with data. However, the available ${\beta }_4$-values, particularly for nuclei in the mass region $16⩽A⩽26$, need be used with caution.

We solve the Faddeev equations for the two meson-one baryon system $\pi \pi N$ and coupled channels using the experimental two-body $t$ matrices for the $\pi N$ interaction as input and unitary chiral dynamics to describe the interaction between the rest of coupled channels. In addition to the $N^{*}(1710)$ obtained before with the $\pi \pi N$ channel, we obtain, for $J^{\pi }=1/2^{+}$ and total isospin of the three-body system $I=1/2$, a resonance peak whose mass is around 2080 MeV and width 54 MeV, while for $I=3/2$ we find a peak around 2126 with 42 MeV of width. These two resonances can be identified with the $N^{*}(2100)$ and the $\Delta (1910)$, respectively. We obtain another peak in the isospin $1/2$ configuration, around 1920 MeV that can be interpreted as a resonance in the $N{a}_0(980)$ and $N{f}_0(980)$ systems.