We investigate $\varphi$ meson photoproduction on the nucleon and ${}^4\mathrm{He}$ targets within a dynamical model approach based on a Hamiltonian which describes the production mechanisms by the Pomeron exchange, meson exchange, $\varphi$ radiation, and nucleon resonance excitation mechanisms. The final $\varphi N$ interactions are included and described by the gluon-exchange, direct $\varphi N$ couplings, and the box diagrams arising from the couplings with $\pi N, \rho N, K\mathrm{\Lambda }$, and $K\mathrm{\Sigma }$ channels. The parameters of the Hamiltonian are determined by the experimental data of $\gamma p\to \varphi p$ from the CLAS Collaboration. The resulting Hamiltonian is then used to predict the coherent $\varphi$-meson production on the ${}^4\mathrm{He}$ targets by using the distorted-wave impulse approximation. For the proton target, the final $\varphi N$ rescattering effects, as required by the unitarity condition, are found to be very weak, which supports the earlier calculations in the literature. For the ${}^4\mathrm{He}$ targets, the predicted differential cross sections are in good agreement with the data obtained by the LEPS Collaboration. The role of each mechanism in this reaction is discussed and predictions for a wide range of scattering angles are presented, which can be tested in future experiments.

Nonyrast, excited states in neutron-rich ${}^{186}\mathrm{W}$ were populated via inelastic-scattering reactions using beams of ${}^{136}\mathrm{Xe}$ nuclei accelerated to 725 and 800 MeV. Levels populated in the reactions were investigated via particle-$\gamma$ coincidence techniques using the Gammasphere array of high-purity germanium detectors and the compact heavy-ion counter, CHICO2. The $K^{\pi }=2^{+}$ ($\gamma$), $K^{\pi }=0^{+}$ and $K^{\pi }=2^{-}$ (octupole) rotational side bands were extended to spins $14\hslash , 12\hslash$, and $13\hslash$, respectively. A staggering pattern observed in the energies of levels in the $K^{\pi }=2^{+}$ band was found to be consistent with a potential that gets softer to vibration in the $\gamma$ degree of freedom with increasing spin. The odd-even staggering of states in the $K^{\pi }=2^{-}$ band was found to exhibit a phase opposite to that seen in the $\gamma$ band; an effect most probably associated with Coriolis coupling to other, unobserved octupole vibrational bands in ${}^{186}\mathrm{W}$.

Background: The deuteron weak binding energy is responsible for high complexity of the deuteron interaction with nuclei that involves also a variety of reactions initiated by the nucleons following the deuteron breakup (BU). An update of both the scarce experimental deuteron database and the incomplete theoretical frame of the deuteron activation analysis is thus needed. Removal of discrepancies between experimental data, and a consistent inclusion of BU as well as of stripping and pickup direct reactions (DR) contributions within deuteron activation analysis, besides preequilibrium emission (PE) and fully equilibrated compound nucleus (CN) decay, are essential, too.

Purpose: Accurate new measurements of low-energy deuteron-induced reaction cross sections for natural Zr target are intended to enhance the related database and the opportunity for a unitary and consistent account of BU, DR, PE, and CN involved reaction mechanisms.

Methods: The activation cross sections of ${}^{90,91m,92m,94m,95m,95g,96,97}\mathrm{Nb}$, ${}^{89m,89,95,97}\mathrm{Zr}$, and ${}^{87m,87g,87,88,90m,91m,94}\mathrm{Y}$ nuclei in deuteron-induced reactions on Zr at energies up to 20 MeV were measured by the stacked-foil technique and high-resolution $\gamma$ spectrometry using the U-120M cyclotron of the Center of Accelerators and Nuclear Analytical Methods (CANAM) infrastructure of the Nuclear Physics Institute of the Czech Academy of Sciences (NPI CAS). Their extended analysis, together with all available data for deuteron interactions with Zr isotopes up to 60 MeV, has included every process from elastic scattering until CN evaporation, with particular attention paid to BU and DR mechanisms.

Results: Newly measured activation excitation functions proved essential for the deuteron database, while analysis of all available data strengthens their consistent account provided that (i) suitable BU and DR assessment is completed by (ii) PE and CN contributions corrected for total-reaction cross-section decrease due to the leakage of the initial deuteron flux towards BU and DR processes.

Conclusions: The suitable description of nuclear mechanisms involved within deuteron-induced reactions on Zr, especially the BU and DR processes, is validated by overall agreement of the calculated and measured cross sections including the new experimental data at low energies.

Using the Brown-Rho (BR) scaling law, several new relativistic Hartree-Fock (RHF) models with chiral limit are thoroughly investigated. The high-density nuclear equation of state (EOS) of RHF with the BR scaling become softer than one without the BR scaling. The EOS of RHF with BR scaling is consistent with the constraint extracted from collective flows and kaon production in heavy-ion collisions. It is found that, with a sizable strength parameter of the mass drop $x=0.126$, the symmetry energy is almost flat at density above 3 times the saturation density ${\rho }_0$, and even decreases slightly. This is caused from the fact that the decline of the potential part of symmetry energy is faster than the increase of the kinetic part of symmetry energy. The decrease of potential part is mainly because the neutron mass $M_n^{*}$ and the proton mass $M_p^{*}$ are close to each other when the density gradually approaches the critical density of chiral limit. For a mass drop of $x=0.092$, since the critical density of chiral limit is higher than one of $x=0.126$, the symmetry energy becomes flat at density above $5{\rho }_0$. While, since the critical density of chiral limit is very high for a small mass drop $x=0.053$, the symmetry energy of RHFs with $x=0.053$ always increases at the entire density domain of this work (below 6 ${\rho }_0$). The maximum mass of neutron star (NS) obtained with present models can satisfy $M=2.08\pm 0.07M_{\odot }$. However, the radius of 1.4 $M_{\odot }$ with the mass drop of $x=0.126$ will surpass the upper limit (13.7 km) extracted from the tidal deformability parameter of coalescence of a NS binary system and the radius of $\text{J0030}+0451$ being $12.{71}_{-1.19}^{+1.14}$ km. The radius of 1.4 $M_{\odot }$ with the mass drop of $x=0.092$ is 13.6 km, closing to 13.7 km and the radius of $\text{J0030}+0451$ being $12.{71}_{-1.19}^{+1.14}$ km. Therefore, the RHF model with BR scaling prefers the mass drop of $x\lesssim 0.092$.

We investigate the properties of the equation of state (EOS), the quark fraction, and the isospin asymmetry for strange quark matter (SQM) under constant magnetic field within the quasiparticle model. Our results indicate that the effect of the magnetic field is important for the properties of strange quark matter, and the recently discovered heavy compact stars PSR $\mathrm{J}0348+0432$, MSR $\text{J0740}+6620$, PSR $\text{J2215}+5135$, and especially the GW190814s secondary component $m_2$ can be well described as quark stars within the quasiparticle model under magnetic fields by approximately using spherically symmetric Tolman-Oppenheimer-Volkov (TOV) equations.

The exotic nuclei have attracted extensive attention in nuclear physics recently. The resonant states are thought to play a critical role at the formation of these exotic phenomena. Here, the complex momentum representation (CMR) method for resonances is combined with the relativistic mean field (RMF) theory applicable to deformed system. The RMF-CMR method for deformed exotic nuclei is established. The theoretical formalism and numerical details are presented. ${}^{75}\mathrm{Cr}$ is chosen as an example, the energies and widths of single-particle levels and their evolutions to deformation ${\beta }_2$ are obtained for resonant states together with bound states. The available potential energy curve shows that ${}^{75}\mathrm{Cr}$ is a deformed nucleus with ${\beta }_2=0.333$. Wave function of the orbit occupied by the last valence neutron consists mainly of $d$-wave components. The corresponding density represents a considerably diffuse distribution, which suggests that ${}^{75}\mathrm{Cr}$ is a $d$-wave deformed halo nucleus. The predication is helpful to explore the deformation halos in experiment for the nuclei in the medium mass region.

We show that the notion of partial dynamical symmetry is robust and founded on a microscopic many-body theory of nuclei. Based on the universal energy density functional framework, a general quantal boson Hamiltonian is derived and shown to have essentially the same spectroscopic character as that predicted by the partial SU(3) symmetry. The principal conclusion holds in two representative classes of energy density functionals: nonrelativistic and relativistic. The analysis is illustrated in application to the axially deformed nucleus ${}^{168}\mathrm{Er}$.

The fusion-evaporation reaction ${}^{32}\mathrm{S}+{}^{28}\mathrm{Si}$ at 125-MeV beam energy was used to populate excited states in ${}^{55}\mathrm{Fe}$. Combining the Gammasphere spectrometer with ancillary devices including the Microball CsI(Tl) array and a shell of neutron detectors, a comprehensive level scheme could be derived. The experimental results are compared with theoretical results from shell-model calculations. Taking into account isospin-symmetry breaking terms is found to considerably improve the shell-model description for ${}^{55}\mathrm{Fe}$. This motivated a predictive case study of near-yrast states in the mirror nucleus ${}^{55}\mathrm{Cu}$.

Isoscalar and isovector effective masses of the nucleon in nuclear medium are explored in the quasielastic electron scattering off nuclei with KIDS (Korea-IBS-Daegu-SKKU) density functional model. Effective masses are varied in the range $(0.7–1.0)M$, where $M$ is the mass of the nucleon in free space. Parameters in the KIDS functional are adjusted to nuclear matter equation of state, energy and radius of selected nuclei, and effective mass of nucleons. The Hartree-Fock equation is solved to obtain the wave functions of the nucleon in target nuclei, and they are plugged in the calculation of electron-nucleus scattering cross sections at the energies of incident electrons 300 MeV–2.5 GeV. The theoretical prediction agrees well with measurement. Dependence on the effective mass is evident: the cross section tends to increase with small isoscalar effective masses. However, the effect of isovector effective mass is negligible. Spectroscopic factors are estimated for the protons in the outermost shells of ${}^{16}\mathrm{O}$, ${}^{40}\mathrm{Ca}$, and ${}^{208}\mathrm{Pb}$. Results are consistent with the values in the literature.

We investigate the deuterium-tritium (DT) fusion process in the presence of strong laser fields with a semiclassical (SC) method. In this model, two nuclei with a given incident kinetic energy that closely approach each other are simulated by tracing the classical Newtonian trajectories in the combined Coulomb repulsive potentials and laser fields. At the nearest position or classical turning point, quantum tunneling through the Coulomb barrier emerges, and its penetrability is estimated with the Wentzel-Kramers-Brillouin formula. Nuclear fusion occurs after the tunneling, and the total fusion cross section takes the Gamow form. We find that the tunneling penetrability can be enhanced dramatically because the nuclei can closely approach each other due to the quiver motion of the charged nuclei driven by the intense laser fields. We then calculate the DT fusion section for a wide range of laser parameters according to various incident nuclei kinetic energies and obtain the phase diagrams for the enhanced DT fusion. We compare our SC results with the quantum results of the Kramers-Henneberger approximation and the Volkov state approximation.

We use data from the Lunar Prospector Neutron Spectrometer to make the second space-based measurement of the free neutron lifetime finding ${\tau }_n=887\pm {14}_{\text{stat}}{}_{-3\text{syst}}^{+7}$ s, which is within $1\sigma$ of the accepted value. This measurement expands the range of planetary bodies where the neutron lifetime has been quantified from space, and by extending the modeling to account for nonuniform elemental composition, we mitigated a significant source of systematic uncertainty on the previous space-based lifetime measurement. This modeling moves space-based neutron lifetime measurement towards the ultimate goal of reducing the magnitude of the systematics on a future space-measurement to the level of those seen in laboratory-based experiments.

The influence of shell effects on fusion of mid-mass nuclei is explored using isotopic chains of K and Ar ions on an oxygen target. Comparison of the reduced excitation functions reveals that the fusion cross section for the open neutron-shell projectile nuclei ${}^{41}\mathrm{K}$ and ${}^{45}\mathrm{K}$ is systematically larger than for the closed neutron-shell projectiles ${}^{39}\mathrm{K}$ and ${}^{47}\mathrm{K}$. The São Paulo fusion model using matter densities from systematics fails to describe the measured excitation functions. Use of more realistic densities from a Dirac-Hartree-Bogoliubov (DHB) approach performs significantly better though it still overpredicts the closed-shell nuclei.

Background: Nuclei approaching $N=Z=40$ are known to exhibit strongly deformed structures and are thought to be candidates for shape coexistence. In the krypton isotopes, ${}^{80,82}\mathrm{Kr}$ are poorly characterized, preventing an understanding of evolving deformation approaching $N=40$.

Purpose: The present work aims to determine electric quadrupole transition strengths and quadrupole moments of ${}^{80,82}\mathrm{Kr}$ in order to better characterize their deformation.

Methods: Sub-barrier Coulomb excitation was employed, impinging the isotopes of krypton on ${}^{196}\mathrm{Pt}$ and ${}^{208}\mathrm{Pb}$ targets. Utilizing a semiclassical description of the safe Coulomb-excitation process $E2$ matrix elements could then be determined.

Results: Eleven new or improved matrix elements are determined in ${}^{80}\mathrm{Kr}$ and seven in ${}^{82}\mathrm{Kr}$. The new $B(E2;0_1^{+}\to 2_1^{+})$ value in ${}^{82}\mathrm{Kr}$ disagrees with the evaluated value by $3\sigma$, which can be explained in terms of deficiencies in a previous Coulomb-excitation analysis.

Conclusions: Comparison of measured $Q_s\left(2_1^{+}\right)$ and $B(E2;0_1^{+}\to 2_1^{+})$ values indicates that neutron-deficient ($N\le 42$) isotopes of krypton are closer to axial deformation than other isotopic chains in the mass region. A continuation of this trend to higher $Z$ may result in Sr and Zr isotopes exhibiting near-axial prolate deformation.

The ${}^{76}\mathrm{Ge}(n,\gamma )$ reaction has been measured at the n_TOF facility at CERN via the time-of-flight technique. Neutron capture cross sections on ${}^{76}\mathrm{Ge}$ are of interest to a variety of low-background experiments, such as neutrinoless double $\beta$ decay searches, and to nuclear astrophysics. We have determined resonance capture kernels up to 52 keV neutron energy and used the new data to calculate Maxwellian-averaged neutron capture cross sections for $k_{\mathrm{B}}T$ values of 5 to 100 keV.

The mass dependence of the transverse flow for $Z=1$–5 fragments from the collisions of ${}^{40}\mathrm{Ar}+{}^{27}\mathrm{Al}, {}^{40}\mathrm{Ar}+{}^{48}\mathrm{Ti}$, and ${}^{40}\mathrm{Ar}+{}^{58}\mathrm{Ni}$ at 47 MeV/nucleon is investigated experimentally in this article. The transverse flow values are determined using the in-plane components of the fragment transverse momenta, where three conventional methods, i.e., the kinetic flow tensor method, the transverse momentum analysis method, and the azimuthal correlation method, are applied to reconstruct the reaction plane in an event-by-event basis. It is demonstrated from the comparison of the present experimental mass dependent flow measurements and the model simulations using an improved antisymmetrized molecular dynamics model that the experimentally observed abnormal $\alpha$ transverse flow enhancement is closely related to the reaction plane reconstruction procedure in the flow extraction. We further investigate the physical existence of the abnormal $\alpha$ flow behavior using a two-particle azimuthal correlation method, which allows us to provide the relative flow magnitude information with an identification of fragment charge number without the knowledge of the reaction plane differing from the three conventional methods. It is found that the relative flow magnitudes deduced from the two-particle azimuthal correlation functions with an identification of $Z$, with the correction for the recoil effect imposed by the momentum conservation, show a monotonically increasing trend as a function of fragment charge number, with no exception of the $\alpha$ flow enhancement. These results, in addition to those from the improved antisymmetrized molecular dynamics model simulations, definitely provide experimental evidences for the inexistence of the abnormal $\alpha$ flow behavior in the heavy-ion collisions at the present incident energy region in nature.

The role of dynamical pairing in induced fission dynamics is investigated using the time-dependent generator coordinate method in the Gaussian overlap approximation, based on the microscopic framework of nuclear energy density functionals. A calculation of fragment charge yields for induced fission of ${}^{228}\mathrm{Th}$ is performed in a three-dimensional space of collective coordinates that, in addition to the axial quadrupole and octupole intrinsic deformations of the nuclear density, also includes an isoscalar pairing degree of freedom. It is shown that the inclusion of dynamical pairing has a pronounced effect on the collective inertia, the collective flux through the scission hypersurface, and the resulting fission yields, reducing the asymmetric peaks and enhancing the contribution of symmetric fission, in better agreement with the empirical trend.

We construct a quark target model (QTM) to incorporate intrinsic glue into effective low-energy models of QCD, which often contain only quark degrees of freedom. This method guarantees the gauge invariance of observables order by order in the strong coupling. The quark and gluon PDFs for the dressed quarks are obtained in the QTM at leading order. We demonstrate gauge invariance of the results by comparing both covariant and light cone gauges, with the former including an explicit Wilson line contribution. A key finding is that in covariant gauges the Wilson line can carry a significant amount of the light cone momentum. With coupling strength ${\alpha }_s=0.5$ and dressed quark mass $M_q=0.4\mathrm{GeV}$, we find quark and gluon momentum fractions of ${\langle x\rangle }_q=0.81$ and ${\langle x\rangle }_g=0.19$, where the Wilson line contribution to the quark momentum fraction is $-0.18$. We use the on-shell renormalization scheme and find that at one loop this Wilson line contribution does not depend on the covariant gauge but does vanish in light cone gauge as expected. This result demonstrates that it is crucial to account for Wilson line contributions when calculating quantum correlation functions in covariant gauges. We also consider the impact of a gluon mass using the gauge invariant formalism proposed by Cornwall, and combine these QTM results with two quark-level models to obtain quark and gluon PDFs for the pion.

The interior of a neutron star is expected to be occupied by a neutron ${}^{3}P_2$ superfluid, which is the condensate of spin-triplet $p$-wave Cooper pairs of neutrons with total angular momentum $J=2$. Here we investigate the thermodynamic stability of ${}^{3}P_2$ superfluids in a neutron-star interior under a strong magnetic field. Using the theory incorporating the finite-size correction of the neutron Fermi surface, we show that the spin-polarized phases of ${}^{3}P_2$ superfluids, the magnetized biaxial nematic phase, and the ferromagnetic phase appear in high temperatures and high magnetic fields. These phases were missed in the previous studies using the quasiclassical approximation in which dispersions of neutrons are linearized around the Fermi surface. In particular, the ferromagnetic phase, which is the condensation of Cooper-paired neutrons with fully polarized spins, appears between the normal phase and the biaxial nematic phase and enlarges the thermodynamic stability of ${}^{3}P_2$ superfluids under strong magnetic fields. Furthermore, we present the augmented Ginzburg-Landau theory that incorporates the thermodynamic stability of spin-polarized ${}^{3}P_2$ superfluid phases.

One of the main challenges for ab initio nuclear many-body theory in the coming decade is the growth of computational and storage costs as calculations are extended to increasingly heavy, exotic, and structurally complex nuclei. Here, we investigate the factorization of nuclear interactions as a means to address this issue. We perform singular value decompositions (SVD) of current nucleon-nucleon interactions in partial wave representation and study the dependence of the singular value spectrum on interaction characteristics like regularization schemes and resolution scales. Next, we develop and implement the similarity renormalization group (SRG) evolution of the interaction in terms of the relevant singular vectors, and demonstrate that this SVD-SRG approach accurately preserves two-nucleon observables. We find that low-resolution interactions naturally allow the truncation of the SVD at low rank, and that a small number of relevant components is sufficient to capture the nuclear interaction and perform an accurate SRG evolution, while the Coulomb interaction requires special consideration. The rank is uniform across all partial waves and almost independent of the basis choice in the tested cases. This suggests an interpretation of the relevant singular components as mere representations of a small set of abstract operators that can describe the interaction and its SRG flow. Following the traditional workflow for nuclear interactions, we discuss how the transformation between the center-of-mass and laboratory frames creates redundant copies of the partial wave components when implemented in matrix representation, and we discuss strategies for mitigation. Finally, we test the low-rank approximation to the SRG-evolved interactions in many-body calculations using the in-medium SRG. By including nuclear radii in our analysis, we verify that the implementation of the SRG using the singular vectors of the interaction does not spoil the evolution of other observables.

The isotope ${}^{220}\mathrm{Pa}$ produced in the reaction ${}^{40}\mathrm{Ar}+{}^{187}\mathrm{Re}$ at a beam energy of 198.7 MeV was reinvestigated via the $\alpha$-spectroscopic method. A new $\alpha$-decaying state in ${}^{220}\mathrm{Pa}$ has been observed with an energy $E_{\alpha }=9664\left(40\right)\mathrm{keV}$ and with a half-life $T_{1/2}={233}_{-56}^{+108}\mathrm{ns}$. The spin parity of the state is tentatively suggested to be ($3^{-}$). The $\alpha$ energy and half-life of the ($1^{-}$) ground state are measured to be $E_{\alpha }=9548\left(30\right)\mathrm{keV}$ and $T_{1/2}=0.75\left(8\right)\mu \mathrm{s}$, respectively. The reduced $\alpha$ width, inferred from the present data, fits well into the systematics for $N=129$ isotones.