Shape-phase transition in neutron-rich Cr isotopes around $N=40$ is investigated by employing the collective Hamiltonian approach. The inertial functions for large-amplitude vibration and rotation are evaluated by the local normal modes along the axial quadrupole collective coordinate using the Skyrme and pairing energy-density functionals. The time-odd components of the mean fields are fully included in the derived masses. The low-lying spectra obtained by requantizing the collective Hamiltonian show an excellent agreement with the recent experimental data. Gradual change from spherical to axially deformed shapes in between $N=34$ and 38 is well described.

Lifetimes of the $9/2_1^{-}$ and $3/2_1^{-}$ states in ${}^{63}\mathrm{Co}$ and the $9/2_1^{-}$ state in ${}^{65}\mathrm{Co}$ were measured using the recoil distance Doppler shift and the differential decay curve methods. The nuclei were populated by multinucleon transfer reactions in inverse kinematics. $\gamma$ rays were measured with the EXOGAM Ge array and the recoiling fragments were fully identified using the large-acceptance VAMOS spectrometer. The $E2$ transition probabilities from the $3/2_1^{-}$ and $9/2_1^{-}$ states to the $7/2^{-}$ ground state could be extracted in ${}^{63}\mathrm{Co}$ as well as an upper limit for the $9/2_1^{-}\to 7/2_1^{-}$ $B(E2)$ value in ${}^{65}\mathrm{Co}$. The experimental results were compared to large-scale shell-model calculations in the $\mathit{pf}$ and ${\mathit{pfg}}_{9/2}$ model spaces, allowing us to draw conclusions on the single-particle or collective nature of the various states.

We investigate ${}^6\mathrm{Li}$($n,n^{\prime }){}^6$Li${}^{*}\to d+\alpha$ reactions by using the continuum-discretized coupled-channels method with the complex Jeukenne-Lejeune-Mahaux effective nucleon-nucleon interaction. In this study, the ${}^6\mathrm{Li}$ nucleus is described by a $d+\alpha$ cluster model. The calculated elastic cross sections for incident energies between 7.47 and 24.0 MeV are in good agreement with experimental data. Furthermore, we show that the neutron spectra for ${}^6\mathrm{Li}$ breakup states measured at selected angular points and incident energies can be also reproduced systematically.

We formulate a theoretical model for the $\alpha$ decay of well-deformed even-even nuclei based on the coupled-channel Schrödinger equation. The $\alpha$-decay half-lives and fine structures observed in $\alpha$ decay are well described by the five-channel microscopic calculations. Since the branching ratios to high-spin states are hard to understand in the traditional $\alpha$-decay theories, this success could be important to interpret future observations of heavier nuclei. It is also found that the $\alpha$ transition to high-spin states is a powerful tool to probe the energy spectrum and deformation of daughter nuclei.

The decays of the $\pi d_{3/2}$ ground states of ${}^{156}\mathrm{Ta}$ and ${}^{160}\mathrm{Re}$ have been studied in detail using the GREAT spectrometer. More than 7000 ${}^{160}\mathrm{Re}$ nuclei were produced in reactions of 290- and 300-MeV ${}^{58}\mathrm{Ni}$ ions with an isotopically enriched ${}^{106}\mathrm{Cd}$ target and separated in flight using the RITU separator. The proton and $\alpha$ decays of the $\pi d_{3/2}$ level were confirmed and the half-life and branching ratios of this state were determined with improved precision to be $t_{1/2}=611\pm 7$ $\mu$s and $b_{\mathrm{p}}=89\pm 1\%$ and $b_{\alpha }=11\pm 1\%$, respectively. The $\alpha$-decay branch populated the ground state of ${}^{156}\mathrm{Ta}$, allowing improved values for the proton-decay energy and half-life to be obtained ($E_p=1011\pm 5$ keV; $t_{1/2}=106\pm 4$ ms). The $\beta$ decay of this level was identified for the first time and a branching ratio of $b_{\beta }=29\pm 3\%$ was deduced. The spectroscopic factors deduced from these measurements are compared with predictions.

The ${\pi }^0\gamma$ invariant mass distribution spectra in the $(\gamma ,{\pi }^0\gamma )$ reaction were measured by the TAPS/ELSA Collaboration to look for the hadron parameters of the $\omega$ meson in the Nb nucleus. We study the mechanism for this reaction, where we consider that the elementary reaction in the Nb nucleus proceeds as $\gamma N\to \omega N;\omega \to {\pi }^0\gamma$. The $\omega$-meson photoproduction amplitude for this reaction is extracted from the measured four-momentum transfer distribution in the $\gamma p\to \omega p$ reaction. The propagation of the $\omega$ meson and the distorted wave function for the ${\pi }^0$ meson in the final state are described by the eikonal form. The $\omega$ and ${\pi }^0$ mesons’ nucleus optical potentials, appearing in the $\omega$ meson propagator and ${\pi }^0$ meson distorted wave function respectively, are estimated using the $t\varrho$ approximation. The effects of pair correlation and color transparency are also studied. The calculated results do not show medium modification for the $\omega$ meson produced in the nucleus for momentum greater than 200 MeV. It occurs because the $\omega$ meson predominantly decays outside the nucleus. The dependence of the cross section on the final-state interaction is also investigated. The broadening of the $\omega$-meson mass distribution spectra is shown to occur due to the large resolution width associated with the detector used in the experiment.

The cross sections of the ${}^{115}\mathrm{Sn}$($\alpha$,$\gamma$)${}^{119}\mathrm{Te}$, ${}^{115}\mathrm{Sn}$($\alpha$,$n$)${}^{118}\mathrm{Te}$, and ${}^{116}\mathrm{Sn}$($\alpha$,$n$)${}^{119}\mathrm{Te}$ reactions (both on ground and isomeric states) have been measured at effective center-of-mass energies from 9.3 to 14.8 MeV. During a first experiment, enriched self-supporting ${}^{115}\mathrm{Sn}$ (51.2%) $+$ ${}^{116}\mathrm{Sn}$ (24.4%) foils were bombarded with an $\alpha$ beam delivered by the Bucharest IFIN-HH Tandem Accelerator. In a second experiment, a highly enriched ${}^{116}\mathrm{Sn}$ target was irradiated in order to disentangle the experimental cross section contributions due to ${}^{115}\mathrm{Sn}$($\alpha$,$\gamma$)${}^{119}\mathrm{Te}$ and ${}^{115}\mathrm{Sn}$($\alpha$,$n$)${}^{118}\mathrm{Te}$ reactions obtained in the first measurement. The beam-induced activity was measured with two large volume HPGe detectors in close geometry. The experimental results were compared with theoretical predictions obtained in the framework of the statistical model.

We have studied nine cases of spontaneous emission of ${}^{14}\mathrm{C}$ clusters in the ground-state decays of the same number of parent nuclei from the trans-lead region, specifically from ${}^{221}\mathrm{Fr}$ to ${}^{226}\mathrm{Th}$, using the preformed cluster model (PCM) of Gupta and collaborators, with choices of spherical, quadrupole deformation (${\beta }_2$) alone, and higher-multipole deformations (${\beta }_2$, ${\beta }_3$, ${\beta }_4$) with cold “compact” orientations ${\theta }^c$ of decay products. The calculated ${}^{14}\mathrm{C}$ cluster decay half-life times are found to be in nice agreement with experimental data only for the case of higher-multipole deformations (${\beta }_2$-${\beta }_4$) and ${\theta }^c$ orientations of cold elongated configurations. In other words, compared to our earlier study of clusters heavier than ${}^{14}\mathrm{C}$, where the inclusion of ${\beta }_2$ alone, with “optimum” orientations, was found to be enough to give the best comparison with data, here for ${}^{14}\mathrm{C}$ cluster decay the inclusion of higher-multipole deformations (up to hexadecapole), together with ${\theta }^c$ orientations, is found to be essential on the basis of the PCM. Interestingly, whereas both the penetration probability and assault frequency work simply as scaling factors, the preformation probability is strongly influenced by the order of multipole deformations and orientations of nuclei. The possible role of $Q$ value and angular-momentum effects are also considered in reference to ${}^{14}\mathrm{C}$ cluster radioactivity.

The $KK\overline{K}$ system is investigated with a coupled-channel approach based on solving the Faddeev equations considering the $\mathit{KK}\overline{K}$, $K\pi \pi$, and $K\pi \eta$ channels and using as input two-body $t$ matrices that generate dynamically the $f_0(980)$ and $a_0(980)$ resonances. In the present calculation, a quasibound state around $1420$ MeV with total isospin $I=1/2$ and spin-parity $J^{\pi }=0^{-}$ is found below the three-kaon threshold. This state can be identified with the $K(1460)$ resonance listed by the Particle Data Group. We also study the $\mathit{KK}\overline{K}$ system in a single-channel three-body potential model with two-body effective $\mathit{KK}$ and $K\overline{K}$ interactions, in which the $K\overline{K}$ interaction is adjusted to reproduce the properties of the $f_0(980)$ and $a_0(980)$ resonances as $K\overline{K}$ bound states, obtaining a very similar result to the one found in the Faddeev approach.

In this paper, we use the mean-field approximation to investigate quark matter described by both SU(2) and SU(3) versions of the Nambu–Jona-Lasinio model at temperatures below 150 MeV and subject to a strong magnetic field. This kind of matter is possibly present in the early stages of heavy-ion collisions and in the interior of protoneutron stars. We have studied symmetric and asymmetric quark matter. The effect of the magnetic field on the effective quark masses and chemical potentials is only felt for quite strong magnetic fields, above $5\times {10}^{18}$ G, with larger effects for the lower densities. Spin polarizations are more sensitive to weaker magnetic fields and are larger for lower temperatures and lower densities. Temperature tends to wash out the magnetic field effects.

Theoretical models of superheavy elements (SHEs) predict a region of increased stability around the proton and neutron shell closures of $Z$ $=$ 114 and $N$ $=$ 184. Therefore a sensitive search for nuclides in the mass range from $A$ $=$ 288 to $A$ $=$ 300 was performed in natural platinum, lead, and bismuth, covering long-lived isotopes of Eka-Pt (Ds, $Z$ $=$ 110), Eka-Pb ($Z$ $=$ 114), and Eka-Bi ($Z$ $=$ 115). Measurements with accelerator mass spectrometry (AMS) at the Vienna Environmental Research Accelerator (VERA) established upper limits for these SHE isotopes in Pt, Pb, and Bi with abundances of <2×10${}^{-15}$, <5×10${}^{-14}$, and <5×10${}^{-13}$, respectively. These results complement earlier searches for SHEs with AMS at VERA in natural thorium and gold, which now amounts to a total number of 37 SHE nuclides having been explored with AMS. In none of our measurements was evidence found for the existence of SHEs in nature at the reported sensitivity level. Even though a few events were observed in the window for ${}^{293}\mathrm{Ek}$a-Bi, a particularly strong pileup background did not allow a definite SHE isotope identification. The present result sets limits on nuclides around the center of the island of stability, essentially ruling out the existence of SHE nuclides with half-lives longer than ∼150 million years.

We investigate the effect of the breakup process on the direct reaction (DR) for ${}^6\mathrm{Li}$. In order to study this effect, we introduce the experimental and semiexperimental ratio factors $R^{\mathrm{expt}}$ and $R^{\mathrm{th}}$ by using the semiexperimental and experimental $\alpha$-production cross sections and DR cross sections. The average values of the ratio $R^{\mathrm{expt}}$ ($R^{\mathrm{th}}$) for the ${}^6\mathrm{Li}+{}^{208}\mathrm{Pb}$ and ${}^6\mathrm{Li}+{}^{209}\mathrm{Bi}$ systems are 0.90 (0.91) and 0.86 (0.85), respectively. From these results, it can be seen that the $\alpha$-production cross sections are the main contribution to the DR cross sections.

The ${}^{150}\mathrm{Nd}$(${}^3\mathrm{He}$,$t$) reaction at $140$ MeV/u and ${}^{150}\mathrm{Sm}$($t$,${}^3\mathrm{He}$) reaction at $115$ MeV/u were measured, populating excited states in ${}^{150}\mathrm{Pm}$. The transitions studied populate intermediate states of importance for the (neutrinoless) $\beta \beta$ decay of ${}^{150}\mathrm{Nd}$ to ${}^{150}\mathrm{Sm}$. Monopole and dipole contributions to the measured excitation-energy spectra were extracted by using multipole decomposition analyses. The experimental results were compared with theoretical calculations obtained within the framework of the quasiparticle random-phase approximation, which is one of the main methods employed for estimating the half-life of the neutrinoless $\beta \beta$ decay ($0\nu \beta \beta$) of ${}^{150}\mathrm{Nd}$. The present results thus provide useful information on the neutrino responses for evaluating the $0\nu \beta \beta$ and $2\nu \beta \beta$ matrix elements. The $2\nu \beta \beta$ matrix element calculated from the Gamow-Teller transitions through the lowest $1^{+}$ state in the intermediate nucleus is maximally about half that deduced from the half-life measured in $2\nu \beta \beta$ direct counting experiments, and at least several transitions through $1^{+}$ intermediate states in ${}^{150}\mathrm{Pm}$ are required to explain the $2\nu \beta \beta$ half-life. Because Gamow-Teller transitions in the ${}^{150}\mathrm{Sm}$($t$,${}^3\mathrm{He}$) experiment are strongly Pauli blocked, the extraction of Gamow-Teller strengths was complicated by the excitation of the $2\hslash \omega$, $\Delta L=0$, $\Delta S=1$ isovector spin-flip giant monopole resonance (IVSGMR). However, the near absence of Gamow-Teller transition strength made it possible to cleanly identify this resonance, and the strength observed is consistent with the full exhaustion of the non-energy-weighted sum rule for the IVSGMR.

We perform an analysis of a binding energy difference called $\delta V_{\mathit{pn}}(N,Z)\equiv -\frac{1}{4}[E(Z,N)-E(Z,N-2)-E(Z-2,N)+E(Z-2,N-2)]$ in the framework of a realistic nuclear model. It has been suggested that $\delta V_{\mathit{pn}}$ values provide a sensitive probe of nuclear structure, and it has been put forward as a primary motivation for the measurement of specific nuclear masses. Using the angular momentum and particle-number projected generator coordinate method and the Skyrme interaction SLy4, we analyze the contribution brought to $\delta V_{\mathit{pn}}$ by static deformation and dynamic fluctuations around the mean-field ground state. Our method gives a good overall description of $\delta V_{\mathit{pn}}$ throughout the chart of nuclei with the exception of the anomaly related to the Wigner energy along the $N=Z$ line. The main conclusions of our analysis of $\delta V_{\mathit{pn}}$, which are at variance with its standard interpretation, are that (i) the structures seen in the systematics of $\delta V_{\mathit{pn}}$ throughout the chart of nuclei can be easily explained combining a smooth background related to the symmetry energy and correlation energies due to deformation and collective fluctuations, (ii) the characteristic pattern of $\delta V_{\mathit{pn}}$ having a much larger size for nuclei that add only particles or only holes to a doubly magic nucleus than for nuclei that add particles for one nucleon species and holes for the other is a trivial consequence of the asymmetric definition of $\delta V_{\mathit{pn}}$ and not due to a the different structure of these nuclei, (iii) $\delta V_{\mathit{pn}}$ does not provide a very reliable indicator for structural changes, (iv)$\delta V_{\mathit{pn}}$ does not provide a reliable measure of the proton-neutron interaction in the nuclear energy density functional (EDF) or of that between the last filled orbits or of the one summed over all orbits, and (v) $\delta V_{\mathit{pn}}$ does not provide a conclusive benchmark for nuclear EDF methods that is superior or complementary to other mass filters such as two-nucleon separation energies or $Q$ values.

A relativistic quark-diquark mass operator with direct and exchange interaction has been constructed in the framework of point form dynamics. The nonstrange baryon spectrum has been calculated and compared with experimental data.

Excited states in ${}^{143}\mathrm{Xe}$, populated in spontaneous fission of ${}^{248}\mathrm{Cm}$, are studied by means of $\gamma$ spectroscopy using the EUROGAM 2 Ge array. We identify three rotational bands in ${}^{143}\mathrm{X}$: a decoupled band originating from the $i_{13/2}$ neutron excitation, a strongly coupled band based on the 5/2${}^{-}$ ground state, and a decoupled band based on the 322.9-keV level with spin 9/2. The new excitation scheme of ${}^{143}\mathrm{Xe}$ is compared to quasiparticle-rotor model calculations, performed with a reflection-symmetric potential.

A rainbow-ladder truncation of QCD’s Dyson-Schwinger equations, constrained by existing applications to hadron physics, is employed to compute the valence-quark parton distribution functions of the pion and kaon. Comparison is made to $\pi$-$N$ Drell-Yan data for the pion’s $u$-quark distribution and to Drell-Yan data for the ratio $u_K(x)/u_{\pi }(x)$: the environmental influence of this quantity is a parameter-free prediction, which agrees well with existing data. Our analysis unifies the computation of distribution functions with that of numerous other properties of pseudoscalar mesons.

We have developed a fully consistent framework for calculations in the quasiparticle random-phase approximation (QRPA) with $\mathrm{NN}$ interactions from the Similarity Renormalization Group (SRG) and other unitary transformations of realistic interactions. The consistency of our calculations, which use the same Hamiltonian to determine the Hartree-Fock-Bogoliubov ground states and the residual interaction for QRPA, guarantees an excellent decoupling of spurious strength, without the need for empirical corrections. While work is under way to include SRG-evolved $3N$ interactions, we presently account for some $3N$ effects by means of a linearly density-dependent interaction, whose strength is adjusted to reproduce the charge radii of closed-shell nuclei across the whole nuclear chart. As a first application, we perform a survey of the monopole, dipole, and quadrupole response of the calcium isotopic chain and of the underlying single-particle spectra, focusing on how their properties depend on the SRG parameter $\lambda$. Unrealistic spin-orbit splittings suggest that spin-orbit terms from the $3N$ interaction are called for. Nevertheless, our general findings are comparable to results from phenomenological QRPA calculations using Skyrme or Gogny energy density functionals. Potentially interesting phenomena related to low-lying strength warrant more systematic investigations in the future.

The fast-stage nucleon emission of proton-nucleus (pA) reactions from 300$A$ MeV to 1.8$A$ GeV has been investigated using the quantum molecular-dynamics model. It is found that the sideward angular spectrum of nucleon emission presents an interesting Mach-like structure at the early stage of the collision (tens of fm/$c$). The sideward angular peak value varies from about 45${}^{°}$ to near 73${}^{°}$, depending on the bombarding energy. Nucleons emitted from the vicinity of the sideward peak tend to have a fixed momentum value about 0.5 GeV/$c$, independent of the bombarding energy as well as the impact parameter. Additionally, the sideward angular peak value is almost independent of the equation of state, indicating that binary collision at the early fast stage in the intermediate energy pA reaction plays an important role in the emergence of Mach-like emission.

A field-theory-based approach to pion photoproduction off the nucleon is used to derive a microscopically consistent formulation of the fully dressed electromagnetic nucleon current in an effective Lagrangian formalism. It is shown how the rigorous implementation of local gauge invariance at all levels of the reaction dynamics provides equations that lend themselves to practically manageable truncations of the underlying nonlinearities of the problem. The requirement of consistency also suggests a novel way of treating the pion photoproduction problem. Guided by a phenomenological implementation of gauge invariance for the truncated equations that has proved successful for pion photoproduction, an expression for the fully dressed nucleon current is given that satisfies the Ward-Takahashi identity for a fully dressed nucleon propagator as a matter of course. Possible applications include meson photo- and electroproduction processes, bremsstrahlung, Compton scattering, and ${\mathit{ee}}^{\prime }$ processes off nucleons.