A detailed $\beta$-decay spectroscopic study of ${}^{22}\mathrm{Al}$ was performed at the Radioactive Ion Beam Line in Lanzhou. With the $\beta \text{−}\gamma$-particle coincidence measurement by a high-resolution DSSD particle detection array and a high efficiency $\gamma$-ray detection array, total eight excited states in ${}^{22}\mathrm{Mg}$ fed by Gamow-Teller transitions was newly identified. The one-proton, two-proton, and $\alpha$ decays of the IAS at 14046(5) keV in ${}^{22}\mathrm{Mg}$, which were partly observed in different experiments before, were identified simultaneously in the present work, providing accurate spectroscopic information about its decay. A more complete $\beta$-decay scheme of ${}^{22}\mathrm{Al}$ was constructed and compared to the shell-model calculations with the USD-type Hamiltonians, USDC and USDB.

A different alternative approach to calculate the ratio of the surface to volume components of the nuclear symmetry energy is proposed in the framework of the coherent density fluctuation model (CDFM). An alternate expression (scheme II) for the ratio is derived consistently within the model. This expression appears in a form more direct and physically motivated than the expression (scheme I) that was used in our previous works within the CDFM and avoids preliminary assumptions and mathematical ambiguities in scheme I. The calculations are based on the Skyrme and Brueckner energy-density functionals for nuclear matter and on the nonrelativistic Brueckner-Hartree-Fock method with realistic Bonn B and Bonn CD nucleon-nucleon potentials. The approach is applied to isotopic chains of Ni, Sn, and Pb nuclei using nuclear densities obtained in self-consistent Hartree-Fock$+\mathrm{BCS}$ calculations with the SLy4 Skyrme effective interaction. The applicability of both schemes within the CDFM is demonstrated by a comparison of the results with the available empirical data and with results of other theoretical studies of the considered quantities. Although in some instances the results obtained for the studied ratio and the symmetry energy components are rather close in both schemes, the proposed scheme II leads to more realistic values that agree better with the empirical data and exhibits conceptual and operational advantages.

Multistep effects among bound, resonant, and nonresonant states have been investigated by the continuum-discretized coupled-channels method (CDCC). In the CDCC, a resonant state is treated as multiple states fragmented in a resonance energy region, although it is described as a single state in usual coupled-channels calculations. For such the fragmented resonant states, one-step, and multistep contributions to the cross sections should be carefully discussed because the cross sections obtained by the one-step calculation depend on the number of those states, which corresponds to the size of the model space. To clarify the role of the multistep effects, we propose the one-step calculation without model-space dependence for the fragmented resonant states. Furthermore, we also discuss the multistep effects among the ground, $2_1^{+}$ resonant, and nonresonant states in ${}^6\mathrm{He}$ for proton inelastic scattering.

Isomeric states in ${}^{256}\mathrm{No}$ were investigated using internal conversion electron and $\gamma$-ray spectroscopy with the GABRIELA detection system at the focal plane of the SHELS recoil separator, at the Flerov Laboratory for Nuclear Research (FLNR, JINR, Dubna). The nuclei of interest were produced using the highly asymmetric fusion-evaporation reaction ${}^{238}\mathrm{U}({}^{22}\mathrm{Ne},4n){}^{256}\mathrm{No}$. The emission of internal conversion electrons and $\gamma$ rays occurring between a ${}^{256}\mathrm{No}$ implantation and a subsequent $\alpha$-decay event were studied, resulting in the observation of high-$K$ isomerism in this nobelium isotope. The nature of the isomeric states is discussed in terms of possible two- and four-quasiparticle structures.

High-resolution $\gamma$-ray spectroscopy of ${}^{18}\mathrm{N}$ is performed with the Advanced GAmma Tracking Array, following deep-inelastic processes induced by an ${}^{18}\mathrm{O}$ beam on a ${}^{181}\mathrm{Ta}$ target. Six states are newly identified, which together with the three known excitations exhaust all negative-parity excited states expected in ${}^{18}\mathrm{N}$ below the neutron threshold. Spin and parities are proposed for all located states on the basis of decay branchings and comparison with large-scale shell-model calculations performed in the p-sd space, with the YSOX interaction. Of particular interest is the location of the $0_1^{-}$ and $1_2^{-}$ excitations, which provide strong constrains for cross-shell p-sd matrix elements based on realistic interactions and help to simultaneously reproduce the ground and first-excited states in ${}^{16}\mathrm{N}$ and ${}^{18}\mathrm{N}$, for the first time. Understanding the ${}^{18}\mathrm{N}$ structure may also have significant impact on neutron-capture cross-section calculations in r-process modeling including light neutron-rich nuclei.

We quantify the extent to which future experiments will test the existence of neutrinoless double-$\beta$ decay mediated by light neutrinos with inverted-ordered masses. While it remains difficult to compare measurements performed with different isotopes, we find that future searches will fully test the inverted-ordering scenario, as a global, multi-isotope endeavor. They will also test other possible mechanisms driving the decay, including a large uncharted region of the allowed parameter space assuming that neutrino masses follow the normal ordering.

There is an ongoing quest to improve on the spectroscopic quality of nuclear energy density functionals (EDFs) of the Skyrme type through extensions of its traditional form. One direction for such activities is the inclusion of terms of higher order in gradients in the EDF. We report on exploratory symmetry-breaking calculations performed for an extension of the Skyrme EDF that includes central terms with four gradients at next-to-next-to-leading order (N2LO) and for which the high-quality parametrization SN2LO1 has been constructed recently [Becker et al., Phys. Rev. C 96, 044330 (2017)]. Up to now, the investigation of such functionals with higher-order terms was limited to infinite matter and spherically symmetric configurations of singly and doubly magic nuclei. We address here nuclei and phenomena that require us to consider axial and nonaxial deformation, both for reflection-symmetric and also reflection-asymmetric shapes, as well as the breaking of time-reversal invariance. Achieving these calculations demanded a number of formal developments. These all resulted from the formulation of the N2LO EDF requiring the introduction of new local densities with additional gradients that are not present in the EDF at NLO. Their choice is not unique, but can differ in the way the gradients are coupled. While designing a numerical implementation of N2LO EDFs in Cartesian three-dimensional coordinate-space representation, we have developed a novel definition and a new unifying notation for normal and pair densities that contain gradients at arbitrary order. Besides having mnemonic advantages, the new notation allows for the easy identification of redundancies and reducibilities in a given set of local densities, and the new definition makes it straightforward to construct densities that automatically adopt the symmetries of the many-body state they are constructed from. The resulting scheme resolves several issues with some of the choices that have been made for local densities in the past, in particular when breaking time-reversal symmetry. Guided by general practical considerations, we propose an alternative form of the N2LO contribution to the Skyrme EDF that is built from a different set of densities. It has exactly the same physics content, but is much more efficient to handle in formal discussions and, compared to the original formulation, leads to a substantial reduction of computational cost and memory requirements in deformed codes. As representative examples for the performance of SN2LO1, we have chosen the ground states of even-even Kr and Nd isotopes, the fission barrier of ${}^{240}\mathrm{Pu}$, as well as the superdeformed rotational band of ${}^{194}\mathrm{Hg}$. Overall, for the nuclei and phenomena studied here, the SN2LO1 parametrization does not yet present a systematic improvement over standard NLO parametrizations. This finding calls for improved fit protocols that better discriminate between NLO and N2LO terms and better exploit the unique features of the additional degrees of freedom offered by the latter.

Background: Giant resonance (GR) is a typical collective mode of vibration. The deformation splitting of the isovector (IV) giant dipole resonance is well established. However, the splitting of GRs with other multipolarities is not well understood.

Purpose: I explore the IV monopole and quadrupole excitations and attempt to obtain the generic features of IV giant resonances in deformed nuclei by investigating the neutral and charge-exchange channels simultaneously.

Method: I employ a nuclear energy-density functional (EDF) method: the Skyrme-Kohn-Sham-Bogoliubov and the quasiparticle random-phase approximation are used to describe the ground state and the transition to excited states.

Results: I find the concentration of the monopole strengths in the energy region of the isobaric analog or Gamow-Teller resonance irrespective of nuclear deformation, and the appearance of a high-energy giant resonance composed of the particle-hole configurations of $2\hslash {\omega }_0$ excitation. Splitting of the distribution of the strength occurs in the giant monopole and quadrupole resonances due to deformation. The lower $K$ states of quadrupole resonances appear lower in energy and possess the enhanced strengths in the prolate configuration, and vice versa in the oblate configuration, while the energy ordering depending on $K$ is not clear for the $J=1$ and $J=2$ spin-quadrupole resonances.

Conclusions: The deformation splitting occurs generally in the giant monopole and quadrupole resonances. The $K$ dependence of the quadrupole transition strengths is largely understood by the anisotropy of density distribution.

Based on the isospin-dependent Boltzmann-Uehling-Uhlenbeck (IBUU) transport model, pion production and absorption are thoroughly studied in the central collision of $\text{Au}+\text{Au}$ at a beam energy of 400 MeV/nucleon. It is found that the pions are first produced by hard $\mathrm{\Delta }$ decay at an average density around $1.75{\rho }_0$, while about 18% of them are absorbed absolutely in the subsequent inelastic collisions. For the free pions observed, more than half of them have been scattered one or more times before they are free from matter, and the higher the scattering numbers of pions, the higher the kinetic energies they possess. These pions, due to longer time of their existence in high density nuclear matter, carry more information about the symmetry energy of nuclear matter at high densities. Moreover, the azimuth dependence and the kinetic energy dependence of the scattering processes and the effect of the symmetry energy are also investigated.

The discovery of nondiffuse sources of gravitational waves through compact-object mergers opens new prospects for the study of physics beyond the Standard Model. In this paper, we study the effects of a new force between quarks, suggested by the gauging of baryon number, on pure neutron matter at supranuclear densities. This leads to a stiffening of the equation of state, allowing neutron stars to be both larger and heavier and possibly accommodating the light progenitor of GW190814 as a neutron star. The role of conventional three-body forces in neutron star structure is still poorly understood, though they can act in a similar way, implying that the mass and radius do not in themselves resolve whether new physics is coming into play. However, a crucial feature of the scenario we propose is that the regions of the new physics parameter space that induce observable changes to neutron star structure are testable at low-energy accelerator facilities. This testability distinguishes our scenario from other classes of new phenomena in dense matter.

To compare fusion-evaporation (FE) and multinucleon transfer (MNT) approaches and make more reliable predictions for producing superheavy nuclei, the unified description of FE and MNT processes is performed in the reaction ${}^{48}\mathrm{Ca}+{}^{238}\mathrm{U}$ within the (DNS) model. We extend the fusion concept in the DNS model based on the deformation degree of freedom. Our calculations support the experimental result [Nishio et al., Phys. Rev. C 77, 064607 (2008)] that compact configuration enhances the fusion probability. The experimental production cross sections of isotopes in FE and MNT processes can be simultaneously reproduced. By comparing the production cross sections in the MNT reaction ${}^{238}\mathrm{U}+{}^{248}\mathrm{Cm}$ with the FE reactions ${}^{48}\mathrm{Ca}+{}^{238}\mathrm{U}$ and ${}^{54}\mathrm{Cr}+{}^{248}\mathrm{Cm}$, we find that the FE process shows great advantages of cross sections for producing Cn isotopes and is the only approach that could produce superheavy elements beyond oganesson.

We analyze the transverse momentum distributions of $pp, p\mathrm{Pb}$, XeXe, and PbPb collisions at different RHIC and LHC energies and centralities as well as the corresponding distributions for Higgs production decaying into $\gamma \gamma$ and $4l$. A simple linear relation is found between the effective thermal temperature and the hard scale, approximately valid for all processes and mainly determined by the hard scale fluctuations. To go further, it is shown that the whole spectrum of $pp$ collisions can be described by a single function showing that the thermal temperature is determined solely by the hard scale and its fluctuations. The possible relation between the multiplicities of the soft and hard scales is explored.

We discuss how to connect the energy levels of two-particle systems trapped by a harmonic-oscillator force to scattering amplitudes, with nucleon-nucleon scattering phase shifts in uncoupled channels as the application. At the center of the proposed framework is the energy-dependent effective field theory that aims to expand observables in a neighborhood around each reference energy, often taken to be one of the energy levels. We also investigate how to disentangle the trapping force at short distances and the intrinsic interaction between the particles.

An approximate but straightforward projection method to molecular many $\alpha$-particle states is proposed and the overlap to the shell model space is determined. This construction of the space poses an alternative to other techniques which use a more general, larger subset of the shell model space and/or use involved numerical methods. The resulting space is in accordance with the shell model, but still contains states which are not completely symmetric under permutations of the $\alpha$ particles, which is one reason to call the construction approximate. A new contribution is the construction of the six- and seven-$\alpha$-particle spaces. The errors of the method propagate toward larger numbers of $\alpha$- and larger shell excitations. In order to show the practicality of the construction proposed, the obtained spaces are applied, within an algebraic cluster model, to ${}^{20}\mathrm{Ne}, {}^{24}\mathrm{Mg}$, and ${}^{28}\mathrm{Si}$, each treated as a many-$\alpha$-particle system. Former results on ${}^{12}\mathrm{C}$ and ${}^{16}\mathrm{O}$ are re-examined.

Angular distributions of the differential cross section for ${}^{20}\mathrm{Ne}+{}^{76}\mathrm{Ge}$ elastic and inelastic scattering at energy 306 MeV are analyzed in the framework of the optical model. The analysis is performed using the coupled-channels mechanism by taking into account the effect of the low-lying states, $0^{+}$ and $2^{+}$ for the projectile ${}^{20}\mathrm{Ne}$ $(E_{\mathrm{ex}.}=1.634 \mathrm{MeV})$, target ${}^{76}\mathrm{Ge}$ $(E_{\mathrm{ex}.}=0.563 \mathrm{MeV})$ nuclei, and their mutual excitation $\left(2^{+},2^{+}\right)$. Results are obtained with the conventional phenomenological Woods-Saxon potential and three different semimicroscopic potentials using the double folding model. Two real cluster potential models are calculated based upon the cluster structure of ${}^{20}\mathrm{Ne}$ nucleus as 5α and $\alpha +{}^{16}\mathrm{O}$. For the sake of comparison, the real of the density-energy-dependent CDM3Y6 potential is considered. The imaginary part for the three real potentials is treated in a standard Woods-Saxon form. The calculations show that the experimental data can be reproduced successfully with a scale factor close to 1. The coupled channels have a weak effect on the elastic scattering with significant differences in calculations of the volume integrals and the total reaction cross sections compared to the available previous study for this reaction. Other future studies are, therefore, required.

A better knowledge of $(n,xn)$ reaction cross sections is important for both reaction modeling and energy applications. This article focuses on inelastic scattering of neutrons off ${}^{238}\mathrm{U}$ for which improvements are needed to better constrain evaluations and solve inconsistencies in nuclear power reactor calculations. A new precise measurement of $(n,xn\gamma )$ reaction cross sections on ${}^{238}\mathrm{U}$ has been performed at the GELINA (Geel Electron LINear Accelerator) neutron facility operated by EC-JRC-Geel (Belgium) with the GRAPhEME (GeRmanium array for Actinides PrEcise MEasurements) setup. The prompt $\gamma$-ray spectroscopy method coupled to time-of-flight measurements is used to extract $(n,xn\gamma )$ cross section values which can be further combined to infer the total neutron inelastic scattering cross section. Cross section data for 18 $\gamma$ transitions (five never measured before) are presented and compared to the data in the literature. Emphasis is especially given to the uncertainty determination to produce partial cross section data as accurate as possible. Due to intrinsic limitations of the experimental method, the use of additional nuclear structure information coupled with theoretical modeling is required to determine the total $(n,n^{\prime })$ cross section over the whole neutron energy range. We have investigated modeling aspects of the ${}^{238}\mathrm{U}(n,n^{\prime }\gamma )$ cross sections related to the description of compound nucleus and preequilibirum mechanisms as well as the discrete part of nuclear structure. Through comparison between experimental and calculated $(n,n^{\prime }\gamma )$ cross sections, we pinpoint inaccuracies in the description of specific reaction mechanisms and challenge recently implemented models. This helps improving the whole modeling of the $(n,n^{\prime })$ reaction.

The very neutron-deficient strongly deformed ${}^{119}\mathrm{Cs}$ nucleus has been studied using the ${}^{58}\mathrm{Ni}({}^{64}\mathrm{Zn},3p$) reaction and the JUROGAM 3 $\gamma$-ray detector array coupled to the MARA recoil-mass separator setup. The excitation energies of all observed bands have been determined, spins and parities have been firmly assigned to most of the observed states. The previously known and the newly identified rotational bands have been extended to very high spin and excitation energy. The configurations of the observed bands are discussed using the particle number conserving cranked shell model. The present study establishes the largest set of rotational bands observed in the proton-rich $A\approx 120$ mass region.

We study many-body resonances in the neuron-rich ${}^8\mathrm{He}$ and the mirror proton-rich ${}^8\mathrm{C}$ using the ${}^4\mathrm{He}+N+N+N+N$ five-body model with the isospin $T=2$ system. Resonances are described with the complex energy eigenvalues as the Gamow states using the complex scaling method. In ${}^8\mathrm{He}$, we obtain five states in which four states are resonances, and in ${}^8\mathrm{C}$ all five states are resonances. We discuss the isospin-symmetry breaking dynamically induced by the Coulomb interaction in the energy spectra and decay widths of the resonances in two mirror nuclei. We predict the resonance energies and decay widths for the future experiments. We also investigate the configurations of valence nucleons above ${}^4\mathrm{He}$ in two nuclei with the $jj$ coupling scheme, and all the states dominantly have the $p$-shell configurations. From the configuration mixing, ${}^8\mathrm{He}$ and ${}^8\mathrm{C}$ give the similar results, which indicates the good symmetry in two nuclei.

In 2017, the STAR Collaboration reported the measurements of hyperon global polarization in heavy ion collisions, suggesting the subatomic fireball fluid created in these collisions as the most vortical fluid. The results show a strongly increasing trend of the signal with decreasing beam energy down to $\sqrt{s_{NN}}=7.7\mathrm{GeV}$. There remains an interesting question: How the signal would change toward even lower energy. In this Letter we perform a systematic study on the beam energy dependence of global and local hyperon polarization phenomena especially in the interesting $\widehat{O}(1–10)\mathrm{GeV}$ region. We find a nonmonotonic trend for the global polarization, which first increases and then decreases when beam energy is lowered from 27 GeV down to 3 GeV. The maximum polarization signal has been identified around $\sqrt{s_{NN}}=7.7\mathrm{GeV}$ in this model whereas the averaged thermal vorticity appears to reach a peak around 3 to 4 GeV. The implications of these results are discussed.

Valuable theoretical predictions of nuclear dipole excitations in the whole nuclear chart are of great interest for different applications, including in particular nuclear astrophysics. We present here the systematic study of the electric-dipole $\left(E1\right)$ photon strength functions combining the microscopic Hartree-Fock-Bogoliubov plus quasiparticle random-phase approximation (HFB $+$ QRPA) model and the parametrizations constrained by the available experimental giant dipole resonance (GDR) data. For about 10 000 nuclei with $8\le \mathrm{Z}\le 124$ lying between the proton and the neutron drip-lines on nuclear chart, the particle-hole (ph) strength distributions are computed using the HFB + QRPA model under the assumption of spherical symmetry and making use of the BSk27 Skyrme effective interaction derived from the most accurate HFB mass model (HFB-27) so far achieved. Large-scale calculations of the BSk27 + QRPA $E1$ photon strength functions are performed in the framework of a specific folding procedure describing the damping of nuclear collective motion empirically. In particular, three phenomenological improvements are considered in this folding procedure. First, two interference factors are introduced and adjusted to reproduce at best the available experimental GDR data. Second, an empirical expression accounting for the deformation effect is applied to describe the peak splitting of the strength function. Third, the width of the strength function is corrected by a temperature-dependent term, which effectively increases the deexcitation photon strength function at low energy. The theoretical $E1$ photon strength functions as well as the extracted GDR peaks and widths are comprehensively compared with available experimental data. A relatively good agreement with data indicates the reliability of the present calculations. Eventually, the astrophysical rates of $(n,\gamma )$ reactions for all the 10 000 nuclei with $8\le Z\le 124$ lying between the proton and the neutron drip lines are estimated using the present $E1$ photon strength functions. The resulting reaction rates are compared with the previous BSk7 + QRPA results as well as the Gogny-HFB + QRPA predictions based on the D1M interaction.