Recent results concerning negative-parity states in ${}^{16}\mathrm{C}$ are analyzed in terms of the shell model and a simple weak-coupling model. We suggest the state at 6.28 MeV is $2^{-}$, and the state near 6.1 MeV is not $3^{-}$, but probably $1^{-}$ ($0^{-}$).

We report on the comprehensive systematics of nearly 400 fusion-evaporation and/or fusion-fission cross-section data for a very large variety of systems over an energy range $\sim 3A$ to $155A$ MeV. Scaled by the reaction cross section and expressed as a function of the center-of-mass energy per nucleon, the fusion cross section displays a universal behavior. Within experimental errors, this behavior does not depend on system mass, mass asymmetry, or system isospin. The deduced homographic functional dependence for complete and summed complete and incomplete fusion excitation functions is derived from basic strong absorption model formulas for reaction cross sections and allows us to draw the main properties of these functions. The limiting energy for the complete fusion and the main characteristics (onset, maximum, and extinction) of the incomplete fusion excitation functions are determined. The complete fusion reaction process disappears around 6.5 MeV/nucleon and the incomplete one disappears at about 13 MeV/nucleon in the center-of-mass frame. The regularity in fusion data is particularly obvious for the evaporation-residue subset of the data ensemble. Adding the fusion-fission data component does not alter the general data trend but somewhat obscures it owing to the larger uncertainty and/or possible normalization problems.

The rapid Gaussian falloff of the oscillator functions at large radius makes them poorly suited for the description of the asymptotic properties of the nuclear wave function, a problem which becomes particularly acute for halo nuclei. We consider an alternative basis for ab initio no-core configuration interaction (NCCI) calculations, built from Coulomb-Sturmian radial functions, allowing for realistic exponential falloff. NCCI calculations are carried out for the neutron halo nuclei ${}^{6,8}\mathrm{He}$, as well as for the baseline case ${}^4\mathrm{He}$, with the JISP16 nucleon-nucleon interaction. Estimates are made for the root-mean-square radii of the proton and matter distributions.

Shape transitions and shape coexistence in the ${}^{70–98}\mathrm{Kr}$ region are studied in a unified view with state-of-the-art beyond-self-consistent mean-field methods based on the Gogny D1S interaction. Beyond-mean-field effects are taken into account through the exact angular-momentum and particle-number restoration and the possibility of axial and nonaxial shape mixing. The results of the low-lying properties of these isotopes are in good agreement with the experimental data when the triaxial degree of freedom is included. Shape transitions from axial-oblate (${}^{70–72}\mathrm{Kr}$) to triaxial-prolate (${}^{74–78}\mathrm{Kr}$) and from spherical-triaxial (${}^{86–92}\mathrm{Kr}$) to axial-oblate (${}^{94–98}\mathrm{Kr}$) ground states are obtained. Additionally, low-lying $0^{+}$ excited states and quasi-$\gamma$ bands are found showing the richness of the collective structure in this region.

We consider the ratio $\mathrm{RE}4=B(E2,4\to 2)/B(E2,2\to 0)$ for the lowest $2^{+}$ and $4^{+}$ states in even-even nuclei. In the rotational and vibrational models and the shell-model calculations considered here, $\mathrm{RE}4$ is greater than 1; however, empirically, using National Nuclear Data Center adopted half-lives and energies for ${}^{48}\mathrm{Cr}$ and ${}^{50}\mathrm{Cr}$, this ratio is less than 1.

Background: The design of new nuclear reactors and transmutation devices requires to reduce the present neutron cross section uncertainties of minor actinides.

Purpose: Improvement of the ${}^{243}\mathrm{Am}$($n,\gamma$) cross section uncertainty.

Method: The ${}^{243}\mathrm{Am}$($n,\gamma$) cross section has been measured at the n_TOF facility at CERN with a ${\mathrm{BaF}}_2$ total absorption calorimeter, in the energy range between 0.7 eV and 2.5 keV.

Results: The ${}^{243}\mathrm{Am}$($n,\gamma$) cross section has been successfully measured in the mentioned energy range. The resolved resonance region has been extended from 250 eV up to 400 eV. In the unresolved resonance region our results are compatible with one of the two incompatible capture data sets available below 2.5 keV. The data available in EXFOR and in the literature have been used to perform a simple analysis above 2.5 keV.

Conclusions: The results of this measurement contribute to reduce the ${}^{243}\mathrm{Am}$($n,\gamma$) cross section uncertainty and suggest that this cross section is underestimated up to 25% in the neutron energy range between 50 eV and a few keV in the present evaluated data libraries.

The interplay between shear and bulk viscosities on the flow harmonics, $v_n$'s, at the BNL Relativistic Heavy Ion Collider is investigated using the newly developed relativistic $2+1$ hydrodynamical code v-usphydro that includes bulk and shear viscosity effects both in the hydrodynamic evolution and at freeze-out. While shear viscosity is known to attenuate the flow harmonics, we find that the inclusion of bulk viscosity decreases the shear viscosity-induced suppression of the flow harmonics, bringing them closer to their values in ideal hydrodynamical calculations. Depending on the value of the bulk viscosity to entropy density ratio, $\zeta /s$, in the quark-gluon plasma, the bulk viscosity-driven suppression of shear viscosity effects on the flow harmonics may require a reevaluation of the previous estimates of the shear viscosity to entropy density ratio, $\eta /s$, of the quark-gluon plasma previously extracted by comparing hydrodynamic calculations to heavy-ion data.

We examine the impact of the strength of the $E_R=127$ keV, ${}^{26}\mathrm{Al}\left(p,\gamma \right){}^{27}\mathrm{Si}$ resonance on ${}^{26}\mathrm{Al}$ production in classical nova explosions and asymptotic giant branch (AGB) stars. Thermonuclear ${}^{26}\mathrm{Al}\left(p,\gamma \right){}^{27}\mathrm{Si}$ reaction rates are determined using different assumed strengths for this resonance and representative stellar model calculations of these astrophysical environments are performed using these different rates. Predicted ${}^{26}\mathrm{Al}$ yields in our models are not sensitive to differences in rates determined using zero and a commonly stated upper limit corresponding to $\omega {\gamma }_{\mathrm{UL}}=0.0042$ $\mu \mathrm{eV}$ for this resonance strength. Yields of ${}^{26}\mathrm{Al}$ decrease by 6% and, more significantly, up to 30%, when a strength of $24\times \omega {\gamma }_{\mathrm{UL}}=0.1$ $\mu \mathrm{eV}$ is assumed in the adopted nova and AGB star models, respectively. Given that the value of $\omega {\gamma }_{\mathrm{UL}}$ was deduced from a single, background-dominated ${}^{26}\mathrm{Al}({}^3\mathrm{He},d){}^{27}\mathrm{Si}$ experiment where only upper limits on differential cross sections were determined, we encourage new experiments to confirm the strength of the 127-keV resonance.

Ultralow-background experiments, such as neutrinoless double-β decay, solar neutrino, and dark-matter searches, are carried out deep underground to escape background events created by cosmic-ray muons passing through the detector volumes. However, such experiments may nevertheless be limited in sensitivity by cosmogenically induced backgrounds. This limit can be attributable to cosmogenically created radioactive isotopes produced either in situ during operation or prior to construction when the detector construction materials are above ground. An accurate knowledge of the production of the latter source of background is of paramount importance to be able to interpret the results of low-background experiments. One way to deal with the characterization of cosmogenic background production is to use Monte Carlo simulations to model the spallation reactions arising from cosmic-ray neutrons, protons, and muons. The objective of this work was to evaluate the degree of accuracy that such simulations could provide by comparing measurements for various materials to results from two standard Monte Carlo codes using the same physics model for generating intranuclear cascades. The simulated results from both codes provide the correct trends of neutron production with increasing material density. However, there was substantial disagreement between the models and experimental results for lower-density materials of Al, Fe, and Cu. The model values, when normalized to the Pb experimental results, show disagreement with experiment by a factor of about two for Fe and Cu and significantly greater for Al. It is concluded that additional neutron-induced spallation measurements are required to refine models routinely employed in underground physics research. Further data collection against the above materials is an initial list for benchmarking.

An “event-shape-twist” technique is proposed to study the longitudinal dynamics of harmonic flow, in particular the effects of rapidity fluctuation and event-plane de-correlation. This technique can distinguish between two types of rapidity de-correlation effects: a systematic rotation versus a random fluctuation of flow angles along the rapidity direction. The technique is demonstrated and the magnitude of the two de-correlation effects is predicted by using a multiphase transport model via a single-particle analysis and a two-particle correlation analysis. An observed de-correlation can be attributed to a systematic rotation of event-plane angle along the pseudorapidity, consistent with a collective response to an initial state twist of the fireball proposed by Bozek et al. This rotation is also observed for several higher-order harmonics with the same sign and similar magnitudes.

Event-by-event fluctuations of observables are often modeled using the Monte Carlo Glauber model, in which the energy is initially deposited in sources associated with wounded nucleons. In this paper, we analyze in detail the correlations between these sources in proton-nucleus and nucleus-nucleus collisions. There are correlations arising from nucleon-nucleon correlations within each nucleus, and correlations due to the collision mechanism, which we dub twin correlations. We investigate this new phenomenon in detail. At the Brookhaven Relativistic Heavy Ion Collider and CERN Large Hadron Collider energies, correlations are found to have modest effects on size and eccentricity fluctuations, such that the Glauber model produces to a good approximation a collection of independent sources.

The effect of the spin-orbit coupling in heavy ion collisions is investigated based on an updated version of the ultrarelativistic quantum molecular dynamics (UrQMD) model, in which the Skyrme potential energy density functional is employed. And in particular, the spin-orbit coupling effects on the directed and elliptic flows of free nucleons emitted from ${}^{197}\mathrm{Au}+{}^{197}\mathrm{Au}$ collisions as functions of both the beam energy and the impact parameter are studied. Our results show that the net contribution of the spin-orbit term to flows of nucleons is negligible, whereas a directed flow splitting between spin-up and spin-down nucleons is visible, especially at large impact parameters, and a peak of the splitting is found at the beam energy around 150 $\mathrm{MeV}/\mathrm{nucleon}$. We also found that the directed flow splitting between spin-up and spin-down neutrons is comparable with the neutron directed flow difference calculated by a soft and a stiff symmetry energy, indicating that the directed flow of neutrons cannot be used to pin down the stiffness of symmetry energy any more without considering the spin degree of freedom in models in the case of spin polarization.

We treat proton-neutron pairing amplitudes, in addition to the nuclear deformation, as generator coordinates in a calculation of the neutrinoless double-$\beta$ decay of ${}^{76}\mathrm{Ge}$. We work in two oscillator shells, with a Hamiltonian that includes separable terms in the quadrupole, spin-isospin, and pairing (isovector and isoscalar) channels. Our approach allows larger single-particle spaces than the shell model and includes the important physics of the proton-neutron quasiparticle random-phase approximation (QRPA) without instabilities near phase transitions. After comparing the results of a simplified calculation that neglects deformation with those of the QRPA, we present a more realistic calculation with both deformation and proton-neutron pairing amplitudes as generator coordinates. The future should see proton-neutron coordinates used together with energy-density functionals.

Nucleon pole contribution in the $pp\to pp{K}^{+}{K}^{-}$ reaction below the threshold of the production of the $\varphi$ meson is studied within the effective Lagrangian approach. It is assumed that the $K^{-}p$ final state originates from the decay of the hyperons $\Lambda \left(1115\right)$ and $\Lambda \left(1405\right)$. In addition to the $pp$ final state interaction (FSI) parametrized using the Jost function, we have also considered the $K^{+}{K}^{-}$ FSI with the techniques of the chiral unitary approach, where the scalar mesons $f_0\left(980\right)$ and $a_0\left(980\right)$ were dynamically generated. Hence, the contributions from scalar mesons $f_0\left(980\right)$ and $a_0\left(980\right)$ occur through the $K^{+}{K}^{-}$ FSI. It is shown that the available experimental data are well reproduced, especially the total cross sections and the invariant mass distributions of $pp$ and $K^{+}{K}^{-}$. Furthermore, different forms of the couplings (pseudoscalar and pseudovector) for the $\pi NN$ interaction and different strengths for the proton-proton FSI are also investigated. It is found that the contributions from hyperons $\Lambda \left(1115\right)$ and $\Lambda \left(1405\right)$ are different between these two kinds of couplings. On the other hand, the effects of the proton-proton FSI can be adjusted by the cutoff parameters used in the form factors.

An effective $\alpha$-particle equation is derived for cases where an $\alpha$ particle is bound to a doubly magic nucleus. As an example, we consider ${}^{212}\mathrm{Po}$ with the $\alpha$ on top of the ${}^{208}\mathrm{Pb}$ core. We consider the core nucleus infinitely heavy, so that the $\alpha$ particle moves with respect to a fixed center; that is, recoil effects are neglected. The fully quantal solution of the problem is discussed. The approach is inspired by the Tohsaki-Horiuchi-Schuck-Röpke wave function concept that has been successfully applied to light nuclei. Shell-model calculations are improved by including four-particle ($\alpha$-like) correlations that are of relevance when the matter density becomes low. In the region where the $\alpha$-like cluster penetrates the core nucleus, the intrinsic bound-state wave function transforms at a critical density into an unbound four-nucleon shell-model state. Exploratory calculations for ${}^{212}\mathrm{Po}$ are presented. Such preformed cluster states are very difficult to describe with shell-model calculations. Reasons for the different physics behavior of an $\alpha$-like cluster with respect to a deuteron-like cluster are discussed.

The $\gamma$ production cross sections from neutron inelastic scattering on ${}^{24}\mathrm{Mg}$ were measured for neutron energies up to 18 MeV at GELINA (the Geel Linear Accelerator), the neutron source operated by EC-JRC-IRMM, Belgium. The level cross section and the total inelastic cross section were determined. We used the GAINS (Gamma Array for Inelastic Neutron Scattering) spectrometer with seven large-volume high-purity germanium (HPGe) detectors placed at ${110}^{\circ }$ and ${150}^{\circ }$ with respect to the beam direction. The neutron flux was determined with a ${}^{235}\mathrm{U}$ fission chamber. The results are compared with calculations performed with the talys 1.6 code using the default settings.

The purpose of this paper is to develop an alternative theory of deuteron stripping to resonance states based on the surface-integral formalism of Kadyrov et al. [Ann. Phys. 324, 1516 (2009)] and continuum-discretized coupled channels (CDCC). First we demonstrate how the surface-integral formalism works in the three-body model and then we consider a more realistic problem in which a composite structure of target nuclei is taken via optical potentials. We explore different choices of channel wave functions and transition operators and show that a conventional CDCC volume matrix element can be written in terms of a surface-integral matrix element, which is peripheral, and an auxiliary matrix element, which determines the contribution of the nuclear interior over the variable $r_{nA}$. This auxiliary matrix element appears because of the inconsistency in treating of the $n\text{−}A$ potential: This potential should be real in the final state to support bound states or resonance scattering and complex in the initial state to describe $n\text{−}A$ scattering. Our main result is formulation of the theory of the stripping to resonance states using the prior form of the surface-integral formalism and CDCC method. It is demonstrated that the conventional CDCC volume matrix element coincides with the surface matrix element, which converges for the stripping to the resonance state. Also the surface representation (over the variable ${\mathbf{r}}_{nA}$) of the stripping matrix element enhances the peripheral part of the amplitude although the internal contribution does not disappear and increases with an increase of the deuteron energy. We present calculations corroborating our findings for both stripping to the bound state and the resonance.

A model developed previously to investigate the electromagnetic production of strangeness from the proton is used to investigate single and double recoil polarization observables in the reaction $ep\to e^{\prime }{K}^{+}\Lambda$ in the relativistic impulse approximation. The formalism is based on a tree-level, effective Lagrangian model, which incorporates a variety of baryon resonances with spins up to $\frac{5}{2}$ and the two kaon resonances, $K^{☆}\left(892\right)$ and $K1\left(1270\right)$. The parameters of the model were fit to a large pool of photoproduction data from the CLAS, GRAAL, SAPHIR, and LEPS collaborations and to CLAS data for the virtual photoproduction structure functions ${\sigma }_U,{\sigma }_T,{\sigma }_L,{\sigma }_{TT},{\sigma }_{LT}$, and ${\sigma }_{L{T}^{\prime }}$. Using two different versions of this model, results are presented for three recoil polarization asymmetries that have been measured recently at CLAS. A new fit is then presented which incorporates the new polarization data in the fitted data set. Results obtained with this new fit are presented for six recoil polarization asymmetries and compared with results from one of the previous fits.