The elastic and inelastic cross sections of ${}^6\mathrm{Li}$ on ${}^{28}\mathrm{Si}$ at 240 MeV, and quasielastic cross section of ${}^7\mathrm{Li}$ and ${}^{11}\mathrm{Li}$ on ${}^{28}\mathrm{Si}$ at $177.8$ and 319 MeV, respectively, are analyzed with the coupled-channels method. The collective nuclear level density is used to determine the deformation parameter regarding to the first-excited state of ${}^{28}\mathrm{Si}$. The results are in agreement with the experimental data and indicate the need of using a nuclear structure model such as nuclear level density to reduce the ambiguity between the optical model parameters and the deformation parameter. Additionally, the spin-orbit potential is found to have an important role in reproducing the data of the quasielastic scattering of ${}^7\mathrm{Li}$ and ${}^{11}\mathrm{Li}$ on a ${}^{28}\mathrm{Si}$ target.

The first and the third Zemach moments are obtained, ${\langle r\rangle }_{\left(2\right)}=1.1108\pm 0.0021$ fm and ${\langle r^3\rangle }_{\left(2\right)}=2.889\pm 0.008$ ${\mathrm{fm}}^3$, from the Bayesian analysis of the elastic $ep$ scattering data. The quantitative discussion of the dependence of the results on the parametrization choice is presented and the corresponding systematic uncertainties are estimated—about 0.6% and 1.6% for the first and the third Zemach moments, respectively.

The first lifetime measurement used to study the magnetic response of halo nuclei is presented. The lifetime of the first excited state of the one-neutron halo nucleus ${}^{19}\mathrm{C}$ has been measured by two complementary Doppler-shift techniques with the Gamma-Ray Energy Tracking In-beam Nuclear Array (GRETINA). The $B(M1;3/2^{+}\to 1/2{}_{\mathrm{g}.\mathrm{s}.}^{+}$) strength of 3.21(25)$\times 10{}^{-3}{\mu }_N^2$ determined for this decay represents a strongly hindered $M1$ transition among light nuclei. Shell-model calculations predict a strong hindrance due to the near-degeneracy of the $s_{1/2}$ and $d_{5/2}$ orbitals among neutron-rich carbon isotopes, while tensor corrections and loosely bound effects are necessary to account for the remaining strength.

Self-consistent mean-field (MF) and beyond-mean-field (BMF) calculations of masses, separation energies, and $2_1^{+}$ excitation energies of even-even nuclei where experimental data is available are presented. The functionals used are based on the Gogny D1S and D1M parametrizations and the method includes BMF corrections coming from both axial quadrupole shape mixing and symmetry restorations without assuming Gaussian overlap approximations. A comparison between MF and BMF approaches and the experimental data is provided. Additionally, the convergence of the results and the possible reduction of the magic shell gaps by including BMF effects are also discussed.

Background: In the seminal experiment by Schmidt et al. [Nucl. Phys. A 665, 221 (2000)] in which fission-fragment charge distributions were obtained for 70 nuclides, asymmetric distributions were seen above nucleon number $A\approx 226$ and symmetric ones below. Because asymmetric fission had often loosely been explained as a preference for the nucleus to always exploit the extra binding of fragments near ${}^{132}\mathrm{Sn}$ it was assumed that all systems below $A\approx 226$ would fission symmetrically because available isotopes do not have a proton-to-neutron $Z/N$ ratio that allows division into fragments near ${}^{132}\mathrm{Sn}$. But the finding by Andreyev et al. [Phys. Rev. Lett. 105, 252502 (2010)] did not conform to this expectation because the compound system ${}^{180}\mathrm{Hg}$ was shown to fission asymmetrically. It was suggested that this was a new type of asymmetric fission, because no strong shell effects occur for any possible fragment division.

Purpose: We calculate a reference database for fission-fragment mass yields for a large region of the nuclear chart comprising 987 nuclides. A particular aim is to establish whether ${}^{180}\mathrm{Hg}$ is part of a contiguous region of asymmetric fission, and if so, its extent, or if not, in contrast to the actinides, there are scattered smaller groups of nuclei that fission asymmetrically in this area of the nuclear chart.

Methods: We use the by now well benchmarked Brownian shape-motion method and perform random walks on the previously calculated five-dimensional potential-energy surfaces. The calculated shell corrections are damped out with energy according to a prescription developed earlier.

Results: We have obtained a theoretical reference database of fission-fragment mass yields for 987 nuclides. These results show an extended region of asymmetric fission with approximate extension $74\le Z\le 85$ and $100\le N\le 120$. The calculated yields are highly variable. We show 20 representative plots of these variable features and summarize the main aspects of our results in terms of “nuclear-chart” plots showing calculated degrees of asymmetry versus $N$ and $Z$.

Conclusions: Experimental data in this region are rare: only ten or so yield distributions have been measured, some with very limited statistics. We agree with several measurements with higher statistics. Regions where there might be differences between our calculated results and measurements lie near the calculated transition line between symmetric and asymmetric fission. To draw more definite conclusions about the accuracy of the present implementation of the Brownian shape-motion approach in this region experimental data, with reliable statistics, for a fair number of suitably located additional nuclides are clearly needed. Because the nuclear potential-energy structure is so different in this region compared to the actinide region, additional experimental data together with fission theory studies that incorporate additional, dynamical aspects should provide much new insight.

New ${}^{14}\mathrm{N}(d,p)$ angular distribution data were taken at a deuteron bombarding energy of 16 MeV to locate all narrow peaks up to 15 MeV in excitation. A new shell model calculation is able to reproduce all levels in ${}^{15}\mathrm{N}$ up to 11.5 MeV and is used to characterize a narrow level at 11.236 MeV and to provide a map of single particle strengths. The known levels in ${}^{15}\mathrm{N}$ are then used to suggest mirrors in the lesser known nucleus ${}^{15}\mathrm{O}$. Neutron spectroscopic factors obtained from the present work and proton spectroscopic factors previously published in a ${}^{14}\mathrm{N}({}^3\mathrm{He},d)$ study were used to determine the $2s_{1/2}$ and $1d_{5/2}$ single particle energies for the ${}^{15}\mathrm{N}-{}^{15}\mathrm{O}$ mirror pairs as ${}^{15}\mathrm{N}\left({2s}_{1/2}\right)=7.64$ MeV, ${}^{15}\mathrm{O}\left({2s}_{1/2}\right)=7.11$ MeV, ${}^{15}\mathrm{N}\left({1d}_{5/2}\right)=7.26$ MeV, and ${}^{15}\mathrm{O}\left({1d}_{5/2}\right)=6.98$ MeV. These results confirm the degeneracy of these orbitals and that the ${}^{15}\mathrm{N}-{}^{15}\mathrm{O}$ nuclei are where the transition of the $2s_{1/2}$ orbital transitions from lying below the $1d_{5/2}$ to above it. The $1d_{3/2}$ single particle strength is estimated to be centered around 14 MeV in these nuclei.

The impact of low-energy multipole excitations and pygmy resonances on radiative neutron and proton-capture cross sections in nuclei close to the $\beta$-stability line is investigated. For this purpose, a microscopic theoretical approach based on self-consistent density functional theory and quasiparticle-random-phase-approximation formalism extended with multiphonon degrees of freedom is implemented in a statistical reaction model. The advantage of the method is the microscopic nuclear structure input for unified description of low-energy multiphonon excitations and pygmy and giant resonances. This is found to be important for the understanding of the fine structure and dynamics of the nuclear response function at low energies, which strongly influences nuclear reaction rates of astrophysical relevance. Calculations of the radiative capture cross sections of the reactions ${}^{85}\mathrm{Kr}\left(n,\gamma \right){}^{86}\mathrm{Kr}, {}^{87}\mathrm{Sr}\left(n,\gamma \right){}^{88}\mathrm{Sr}$, and ${}^{89}\mathrm{Y}\left(p,\gamma \right){}^{90}\mathrm{Zr}$ are discussed in comparison with experimental data. For the reactions ${}^{89}\mathrm{Zr}\left(n,\gamma \right){}^{90}\mathrm{Zr}$ and ${}^{91}\mathrm{Mo}\left(n,\gamma \right){}^{92}\mathrm{Mo}$ theoretical predictions of the reaction cross sections are made.

Nuclear clustering, alpha decays, and multiparticle correlations are important components of nuclear dynamics. In this work we put forward the cluster-nucleon configuration interaction model. We use the modern configuration interaction approach with advanced realistic shell-model Hamiltonians in order to study clustering phenomena; the study is facilitated by the algebraic properties of many-nucleon configurations in the harmonic oscillator basis. Using a translationally invariant formalism we built cluster channels that satisfy the Pauli exclusion principle as well as orthogonality and normalization conditions. We formally justify the formalism and demonstrate that, within the new method, clustering strengths satisfy sum rules that are consistent with the statistical properties of nuclear reactions with composite particles. Using properly renormalized cluster form factors our approach appears to resolve long-standing problems related to absolute normalization of the alpha clustering spectroscopic factors and their behavior in $sd$-shell nuclei. Our methods are demonstrated in studies of $\alpha$ spectroscopic factors in $sd$-shell nuclei and in ${}^{16}\mathrm{O}$ treated in $p-sd$ shells. Comparison with experimental data supports the validity of the approach.

Experimental data for central collisions of ${}^{129}\mathrm{Xe}$ on ${}^{119}\mathrm{Sn}$ at beam energies of (a) 32, (b) 39, (c) 45, and (d) 50 MeV/nucleon are compared with results calculated using a hybrid model. We use a transport model (BUU) to obtain the excitation energy per nucleon in the center of mass of the multifragmenting system. The canonical thermodynamic model is then used to determine the temperature which would lead to this excitation energy. With this temperature we use the canonical thermodynamic model to calculate various experimental data such as multiplicities of different composites, probability distribution of the largest cluster, etc. Agreement with data establishes the validity of the model.

Quarkonium at finite temperature is described as an open quantum system whose dynamics are determined by a potential $V_R\left(\mathbf{x}\right)$ and drag coefficient $\eta$, using a path integral with a nonlocal term. Path-integral Monte Carlo calculations determine the Euclidean Green function for this system to an accuracy greater than one part in a thousand and the maximum entropy method is used to determine the spectral function; challenges facing any kind of deconvolution are discussed in detail with the aim of developing intuition for when deconvolution is possible. Significant changes to the quarkonium spectral function in the $1S$ channel are found, suggesting that any description of quarkonium at finite temperature, using a potential, must also carefully consider the effect of dissipation.

Background: The slowest reaction in the first CNO cycle is ${}^{14}\mathrm{N}(p,\gamma ){}^{15}\mathrm{O}$, therefore its rate determines the overall energy production efficiency of the entire cycle. The cross section presents several strong resonance contributions, especially for the ground-state transition. Some of the properties of the corresponding levels in the ${}^{15}\mathrm{O}$ compound nucleus remain uncertain, which affects the uncertainty in extrapolating the capture cross section to the low energy range of astrophysical interest.

Purpose: The ${}^{14}\mathrm{N}(p,\gamma ){}^{15}\mathrm{O}$ cross section can be described by using the phenomenological $R$ matrix. Over the energy range of interest, only the proton and $\gamma$-ray channels are open. Since resonance capture makes significant contributions to the ${}^{14}\mathrm{N}(p,\gamma ){}^{15}\mathrm{O}$ cross section, resonant proton scattering data can be used to provide additional constraints on the $R$-matrix fit of the capture data.

Methods: A 4 MV KN Van de Graaff accelerator was used to bombard protons onto a windowless gas target containing enriched ${}^{14}\mathrm{N}$ gas over the proton energy range from $E_p=1.0$ to 3.0 MeV. Scattered protons were detected at ${\theta }_{\text{lab}}=90, {120}^{\circ }, {135}^{\circ }, {150}^{\circ }$, and ${160}^{\circ }$ using ruggedized silicon detectors. In addition, a 10 MV FN Tandem Van de Graaff accelerator was used to accelerate protons onto a solid Adenine (${\mathrm{C}}_5{\mathrm{H}}_5{\mathrm{N}}_5$) target, of natural isotopic abundance, evaporated onto a thin self-supporting carbon backing, over the energy range from $E_p=1.8$ to 4.0 MeV. Scattered protons were detected at 28 angles between ${\theta }_{\text{lab}}=30.4^{\circ }$ and $167.7^{\circ }$ by using silicon photodiode detectors.

Results: Relative cross sections were extracted from both measurements. While the relative cross sections do not provide as much constraint as absolute measurements, they greatly reduce the dependence of the data on otherwise significant systematic uncertainties, which are more difficult to quantify. The data are fit simultaneously using an $R$-matrix analysis and level energies and proton widths are extracted. Even with relative measurements, the statistics and large angular coverage of the measurements result in more confident values for the energies and proton widths of several levels; in particular, the broad resonance at $E_{\text{c.m.}}=2.21$ MeV, which corresponds to the $3/2^{+}$ level at $E_x=9.51$ MeV in ${}^{15}\mathrm{O}$. In particular, the $s$- and $d$-wave angular-momentum channels are separated.

Conclusion: The relative cross sections provide a consistent set of data that can be used to better constrain a full multichannel $R$-matrix extrapolation of the capture data. It has been demonstrated how the scattering data reduce the uncertainty through a preliminary Monte Carlo uncertainty analysis, but several other issues remain that make large contributions to the uncertainty, which must be addressed by further capture and lifetime measurements.

We study the effects of a strong magnetic field on the proton and neutron spin polarization and magnetic susceptibility of asymmetric nuclear matter within a relativistic mean-field approach. It is shown that magnetic fields $B\sim {10}^{16}–{10}^{17}$ G have noticeable effects on the range of densities of interest for the study of the crust of a neutron star. Although the proton susceptibility is larger for weaker fields, the neutron susceptibility becomes of the same order or even larger for small proton fractions and subsaturation densities for $B>{10}^{16}$ G. We expect that neutron superfluidity in the crust will be affected by the presence of magnetic fields.

Conservation laws in the $1f_{7/2}$ shell model of ${}^{48}\mathrm{Cr}$ found in numeric studies by Escuderos, Zamick, and Bayman [arXiv:nucl-th/0506050 (2005)] and me [K. Neergård, Phys. Rev. C 90, 014318 (2014)] are explained by symmetry under particle-hole conjugation and the structure of the irreps of the symplectic group Sp(4). A generalization is discussed.

Background: The process of $\beta$-delayed fission $\left(\beta \mathrm{DF}\right)$ provides a versatile tool to study low-energy fission in nuclei far away from the $\beta$-stability line, especially for nuclei which do not fission spontaneously.

Purpose: The aim of this paper is to investigate systematic trends in $\beta \mathrm{DF}$ partial half-lives.

Method: A semi-phenomenological framework was developed to systematically account for the behavior of $\beta \mathrm{DF}$ partial half-lives.

Results: The $\beta \mathrm{DF}$ partial half-life appears to exponentially depend on the difference between the $Q$ value for $\beta$ decay of the parent nucleus and the fission-barrier energy of the daughter (after $\beta$ decay) product. Such dependence was found to arise naturally from some simple theoretical considerations.

Conclusions: This systematic trend was confirmed for experimental $\beta \mathrm{DF}$ partial half-lives spanning over seven orders of magnitude when using fission barriers calculated from either the Thomas-Fermi or the liquid-drop fission model. The same dependence was also observed, although less pronounced, when comparing to fission barriers from the finite-range liquid-drop model or the Thomas-Fermi plus Strutinsky integral method.

The parity-violating asymmetries between a longitudinally polarized electron beam and an unpolarized deuterium target have been measured recently. The measurement covered two kinematic points in the deep-inelastic scattering region and five in the nucleon resonance region. We provide here details of the experimental setup, data analysis, and results on all asymmetry measurements including parity-violating electron asymmetries and those of inclusive pion production and beam-normal asymmetries. The parity-violating deep-inelastic asymmetries were used to extract the electron-quark weak effective couplings, and the resonance asymmetries provided the first evidence for quark-hadron duality in electroweak observables. These electron asymmetries and their interpretation were published earlier, but are presented here in more detail.

In the previous work, we performed direct and exclusive measurements of the ${}^8\mathrm{Li}+\alpha$ reaction and provided cross section data for the ${}^8\mathrm{Li}{(\alpha ,n)}^{11}\mathrm{B}$ reaction [Phys. Rev. C 62, 065801 (2000)]. Recently, we reanalyzed the data and obtained additional cross section data for the ${}^8\mathrm{Li}{(\alpha ,\alpha n)}^7\mathrm{Li}$ reaction at center-of-mass energies between 2.0 and 7.0 MeV; the new data complement those of the ${}^8\mathrm{Li}{(\alpha ,n)}^{11}\mathrm{B}$ reaction obtained in the previous work. The sum of their cross sections is consistent with the reaction cross section of the ${}^8\mathrm{Li}+\alpha$ reaction estimated by a classical formula.

Background: Accurate knowledge of the ${}^{13}\mathrm{C}(\alpha ,n){}^{16}\mathrm{O}$ reaction cross section is important for the understanding of the $s$ process in asymptotic giant branch stars, since it is considered to be the main source of neutrons. The subthreshold $1/2^{+}$ state at excitation energy of 6.356 MeV in ${}^{17}\mathrm{O}$ has a strong influence on the reaction cross section at energies relevant for astrophysics. Several experiments have been performed to determine the contribution of this state to the ${}^{13}\mathrm{C}(\alpha ,n){}^{16}\mathrm{O}$ reaction rate. Nevertheless, significant discrepancies between different measurements remain.

Purpose: The aim of this work is to investigate these discrepancies.

Method: An 8 MeV ${}^{13}\mathrm{C}$ beam (below the Coulomb barrier) was used to study the $\alpha$-transfer reaction ${}^6\mathrm{Li}({}^{13}\mathrm{C},d){}^{17}\mathrm{O}$.

Results: The squared Coulomb-modified asymptotic normalization coefficient of the $1/2^{+}$ state in ${}^{17}\mathrm{O}$ measured in this work is ${\left({\tilde{C}}_{\alpha {-}^{13}\text{C}}^{{}^{17}\mathrm{O}(1/2+)}\right)}^2=3.6\pm 0.7{\text{fm}}^{-1}$.

Conclusions: Discrepancy between the results of $\alpha$-transfer experiments have been resolved. However, some discrepancy with the most recent measurement using the Trojan Horse method remains.

Shell evolution is studied in the neutron-rich silicon isotopes ${}^{36,38,40}\mathrm{Si}$ using neutron single-particle strengths deduced from one-neutron knockout reactions. Configurations involving neutron excitations across the $N=20$ and $N=28$ shell gaps are quantified experimentally in these rare isotopes. Comparisons with shell model calculations show that the tensor force, understood to drive the collective behavior in ${}^{42}\mathrm{Si}$ with $N=28$, is already important in determining the structure of ${}^{40}\mathrm{Si}$ with $N=26$. New data relating to cross-shell excitations provide the first quantitative support for repulsive contributions to the cross-shell $T=1$ interaction arising from three-nucleon forces.

We present a novel framework to decompose three-nucleon forces in a momentum-space partial-wave basis. The new approach is computationally much more efficient than previous methods and opens the way to ab initio studies of few-nucleon scattering processes, nuclei, and nuclear matter based on higher-order chiral three-nucleon forces. We use the new framework to calculate matrix elements of chiral three-nucleon forces at next-to-next-to-leading-order and next-to-next-to-next-to-leading-order in large basis spaces and carry out benchmark calculations for neutron matter and symmetric nuclear matter. We also study the size of the individual three-nucleon-force contributions for ${}^3\mathrm{H}$. For nonlocal regulators, we find that the subleading terms, which have been neglected in most calculations so far, provide important contributions. All matrix elements are calculated and stored in a user-friendly way, such that values of low-energy constants as well as the form of regulator functions can be chosen freely.