Several experimental investigations have reported evidence of collective enhancement of the nuclear level density and its fadeout. However, a suitable method is needed for experimental determination of the enhancement factor as a function of excitation energy. In this study, neutron spectra were measured in coincidence with evaporated $\alpha$ particles produced in the reactions ${}^{11}\mathrm{B}+{}^{181}\mathrm{Ta},{}^{197}\mathrm{Au}$. The nuclear level density parameter has been extracted for the $\mathrm{Os}(A\approx 188)$ and $\mathrm{Pb}(A\approx 204)$ isotopes by comparing neutron spectra with statistical model prediction. Evidence for collective enhancement has been found for Os nuclei whereas no such enhancement has been seen for Pb nuclei. The energy-dependent enhancement factor has been extracted by simultaneous fitting of the neutron spectra at various excitation energies. Near a temperature of 0.8 MeV, the enhancement starts to fadeout which is lower than the theoretically predicted temperature of 1.4 MeV for ${}^{187}\mathrm{Os}$. Also, free energy surface calculation shows that the ${}^{187}\mathrm{Os}$ nucleus undergoes a transition from collective prolate to noncollective oblate shape close to the temperature of 0.8 MeV, corroborating the early fadeout. No such shape transition is seen for ${}^{203}\mathrm{Pb}$.

We analyze the isoscalar response related to breathing modes with particular attention being paid to low-lying excitations in neutron-rich nuclei. We use the subtracted second random-phase approximation (SSRPA) to describe microscopically the response. By increasing the neutron excess, we study the evolution of the response in Ca isotopes going from ${}^{40}\mathrm{Ca}$ to ${}^{48}\mathrm{Ca}$ and to ${}^{60}\mathrm{Ca}$ as well as in $N=20$ isotones going from ${}^{40}\mathrm{Ca}$ to ${}^{36}\mathrm{S}$ and to ${}^{34}\mathrm{Si}$. Finally, the case of ${}^{68}\mathrm{Ni}$ is investigated. We predict soft monopole modes in neutron-rich nuclei which are driven by neutron excitations. At variance with dipole pygmy modes, these neutron excitations are not only strongly dominant at the surface of the nucleus but over its entire volume. The effect of the mixing with two particle–two hole configurations induced by the SSRPA model is analyzed. The properties of such soft neutron modes are investigated in terms of their excitation energies, transition densities and wave-function components. Their collectivity is also discussed as a function of the isospin asymmetry and of the mass of the nucleus. The link between such low-energy compression modes and a compressibility modulus introduced for neutron-rich infinite matter is finally studied.

An energy-dependent microscopic optical model potential (OP) is presented to analyze the elastic scattering of protons with incident energies up to 1000 MeV/nucleon on ${}^9\mathrm{Be}$ nucleus. This microscopic optical model is built from the single-folding optical model. The density- and isospin-dependent M3Y-Paris nucleon-nucleon ($NN$) interaction is used for the real and spin-orbit parts and the $NN$-scattering amplitude of the high-energy approximation for the imaginary one. The microscopic complex spin-orbit OP is taken within Breiva-Rook approximation. The partial-wave expansion analysis with this optical model potential fails to reproduce the differential cross-section data at energies larger than 100 MeV/nucleon, a good improvement is obtained by including the surface contribution to the imaginary OP where most of the basic scattering observables are reproduced well at the considered wide energy range. The volume integrals are found to be have interesting energy dependencies and their parametrizations can be used to build an energy-dependent microscopic OP that is used to reproduce the observables at a wide energy range. This study shows that the partial-wave expansion analysis using the folding optical model can be used to analyze the scattering data at high energies as well as at low energies.

In the present work, the pre- and post-scission neutron multiplicities were measured for the reaction ${}^{18}\mathrm{O}+{}^{186}\mathrm{W}$ at different excitation energies populating the compound nucleus ${}^{204}\mathrm{Pb}$, using the National Array of Neutron Detectors (NAND) facility at IUAC, New Delhi, India. Here, we investigated the entrance channel effect on the nuclear dissipation involved in the heavy ion fusion-fission dynamics. The statistical model analysis was performed using the code vecstat. The prescribed reaction ${}^{18}\mathrm{O}+{}^{186}\mathrm{W}$ had similar value of the mass asymmetry as the system ${}^{16}\mathrm{O}+{}^{181}\mathrm{Ta}$ studied earlier, populating the compound nucleus ${}^{197}\mathrm{Tl}$. Specifically, we observed the similar behavior from both the systems against the nuclear dissipation, with the similar value of the mass asymmetry. The role of the entrance channel parameters on the nuclear dissipation was also discussed in the present work.

We outline an extension of the classical Langevin equation to a quantum formulation of the treatment of dissipation and fluctuations of all collective degrees of freedom with unitary evolution of a many-fermion system within an extension of the time-dependent density functional theory. We illustrate the method by computing the distribution of fission fragment yields for ${}^{258}\mathrm{Fm}$ in a quantum hydrodynamic approach and a typical trajectory with full unrestricted density functional theory augmented with dissipation and fluctuations.

In this work, we revisit the thermodynamical self-consistency of the quasiparticle model with the finite baryon chemical potential adjusted to lattice QCD calculations. Here we investigate the possibility that the effective quasiparticle mass is also a function of its momentum $k$, in addition to temperature $T$ and chemical potential $\mu$. It is found that the thermodynamic consistency can be expressed in terms of an integrodifferential equation concerning $k$, $T$, and $\mu$. We further discuss two special solutions, both can be viewed as a sufficient condition for the thermodynamical consistency, while expressed in terms of a particle differential equation. The first case is shown to be equivalent to those previously discussed by Peshier et al. The second one, obtained through an ad hoc assumption, is an intrinsically different solution where the particle mass is momentum dependent. These equations can be solved by using boundary condition determined by the lattice QCD data at vanishing baryon chemical potential. By numerical calculations, we show that both solutions can reasonably reproduce the recent lattice QCD results of the Wuppertal-Budapest and HotQCD Collaborations, and in particular, those concerning finite baryon density. Possible implications are discussed.

The properties of the core-crust transition in neutron stars are investigated using effective nuclear forces of finite range. Special attention is paid to the so-called dynamical method for locating the transition point, which, apart from the stability of the uniform nuclear matter against clusterization, also considers contributions due to finite-size effects. In particular, contributions to the transition density and pressure from the direct and exchange energies are carefully analyzed. To this end, finite-range forces of Gogny, momentum-dependent interaction, and simple effective interaction types are used in the numerical applications. The results from the dynamical approach are compared with those from the popular thermodynamical method that neglects the surface and Coulomb effects in the stability condition. The dependence of the core-crust transition on the stiffness of the symmetry energy of the finite-range models is also addressed. Finally, we analyze the impact of the transition point on the mass, thickness, and fraction of the moment of inertia of the neutron star crust. Prominent differences in these crustal properties of the star are found between using the transition point obtained with the dynamical method or the thermodynamical method. It is concluded that the core-crust transition needs to be ascertained as precisely as possible in order to have realistic estimates of the observed phenomena where the crust plays a significant role.

The influence of polarization effects and temperature effects on the deformations of projectilelike and targetlike densities are taken into account consistently on the potential-energy surface. The evaporation residue cross sections for hot-fusion reactions are investigated within the dinuclear system model. The calculated results have reproduced well the experimental trend and absolute value of the maximum cross sections for $3n$ and $4n$ channels. The new isotopes of ${}^{293,295,296}\mathrm{Og}$ were found to be as large as about 0.1–0.2 pb.

Experiments with intense photon and electron beams have the potential to provide access to nontrivial properties of the recently discovered $d^{*}\left(2380\right)$ hexaquark including its size, structure, magnetic moment, and quadrupole and octupole deformations. In this paper we investigate the sensitivity of ongoing and planned experiments to various properties of the $d^{*}\left(2380\right)$, employing models based on both constituent quark and pion cloud frameworks. Our calculations indicate that for photoinduced reactions on the deuteron, the $d^{*}\left(2380\right)$ is predominantly produced from the $D$-wave component of the deuteron. We confirm earlier findings that the intrinsic quadrupole deformation of the $d^{*}\left(2380\right)$ should be small. We also demonstrate an ability to extract the $d^{*}\left(2380\right)$ magnetic moment and put constraints on the $d^{*}\left(2380\right)M3/E2$ ratio.

In nuclear structure calculations, the choice of a limited model space, due to computational needs, leads to the necessity to renormalize the Hamiltonian as well as any transition operator. Here, we present a study of the renormalization procedure and effects of the Gamow-Teller operator within the framework of the realistic shell model. Our effective shell-model operators are obtained, starting from a realistic nucleon-nucleon potential, by way of the many-body perturbation theory in order to take into account the degrees of freedom that are not explicitly included in the chosen model space. The theoretical effective shell-model Hamiltonian and transition operators are then employed in shell-model calculations, whose results are compared with data of Gamow-Teller transition strengths and double-$\beta$ half-lives for nuclei which are currently of interest for the detection of the neutrinoless double-$\beta$ decay process, in a mass interval ranging from $A=48$ up to $A=136$. We show that effective operators are able to reproduce quantitatively the spectroscopic and decay properties without resorting to an empirical quenching neither of the axial coupling constant $g_A$, nor of the spin and orbital gyromagnetic factors. This should assess the reliability of applying present theoretical tools to this problematic.

The validity of the multinucleon transfer (MNT) approach for deduction of fission barrier heights was investigated in an experiment carried out at the JAEA tandem accelerator facility. By using the ${}^{18}\mathrm{O} + {}^{237}\mathrm{Np}$ reaction, fission barrier heights were inferred from fission probabilities of the nuclei ${}^{239}\mathrm{Np}$ and ${}^{239,240}\mathrm{Pu}$ produced in the $2n$ and $pn/p2n$ transfer channels, respectively. The deduced values of fission barriers agree well with the literature data, thus demonstrating the potential of the MNT reactions for obtaining fission-barrier data for nuclei not accessible for fission studies via neutron- or light charged particle-induced reactions.

Background: Multinucleon transfer reactions at low-energy collisions are considered to be promising for the production of new exotic nuclei, which are difficult to produce by other methods. Theoretical studies are required to provide reliable predictions for the experiments and to help understand the microscopic mechanism in multinucleon transfer reactions.

Purpose: We provide a predictive approach for production cross sections and show how and to what extent the microscopic approach works well in multinucleon transfer reactions.

Methods: We employ the $\text{TDHF}+\text{GEMINI}$ approach, which combines the microscopic time-dependent Hartree-Fock (TDHF) model with the state-of-art statistical model $\text{GEMINI}++$, to take into account both the multinucleon transfer dynamics and the secondary de-excitation process. The properties of primary products in multinucleon transfer process, such as transfer probabilities and primary cross sections, are extracted from TDHF dynamics using the particle-number projection method. Production cross sections for secondary products are evaluated using the statistical model $\text{GEMINI}++$.

Results: We investigate the influence of colliding energies and deformation orientations of target and projectile nuclei on multinucleon transfer dynamics in the reaction ${}^{58}\mathrm{Ni}+{}^{124}\mathrm{Sn}$. More nucleons are observed to transfer in the tip collision than in the side collision. The production cross sections for secondary fragments with $\text{TDHF}+\text{GEMINI}$ calculations well reproduce the experimental measurements at energies close to the Coulomb barrier. At sub-barrier energy, the theoretical results gradually deviate from the experimental data with the increase of the number of transferred neutrons, showing the limitations of a single mean-field approximation in the TDHF approach. Possible origins for this discrepancy are discussed. The total cross sections integrated over all the neutron transfer channels are in good agreement with the experimental data for all the energies. We compare the production cross sections of $\text{TDHF}+\text{GEMINI}$ calculations with those from GRAZING model and find that our approach gives a description as quantitatively good as the semiclassical model, although there is no adjustable parameters for the reaction dynamics in the microscopic TDHF method.

Conclusions: The microscopic $\text{TDHF}+\text{GEMINI}$ approach reasonably reproduces the experimental data at energies close to the Coulomb barrier and well accounts for the multinucleon transfer mechanism. The present studies clearly reveal the applicability of $\text{TDHF}+\text{GEMINI}$ method in multinucleon transfer reactions, which thus is a promising tool for predicting the properties of new reactions.

We derive the formulas for calculating the squeezed back-to-back correlation (SBBC) between a boson and antiboson with nonzero width produced in relativistic heavy-ion collisions. The SBBCs of $D^0$ and $\varphi$ mesons with finite in-medium widths are studied. We find that the finite width can change the pattern of the SBBC function of $D^0{\overline{D}}^0$ with respect to mass. However, the SBBC function of $\varphi \varphi$ is insensitive to the width. In the high-particle-momentum region, the SBBC function of $\varphi \varphi$ increases with particle momentum rapidly and can exceed that of $D^0{\overline{D}}^0$ whether the width is nonzero or not.

We study the photoproduction and electroproductions of the vector kaon off the proton, i.e., ${\gamma }^{(*)}p\to K^{*+}{\pi }^0{\mathrm{\Sigma }}^0$, and investigate the line shape of the ${\pi }^0{\mathrm{\Sigma }}^0$ invariant mass in an effective Lagrangian approach with the inclusion of a $K^{*}N{\mathrm{\Lambda }}^{*}$ interaction. Relevant electromagnetic form factors for the neutral hyperons and charged strange mesons are constructed by considering experimental and theoretical information. We find that the ${\mathrm{\Lambda }}^{*}$ peak is clearly observed for the photoproduction and electroproductions with the finite $K^{*}N{\mathrm{\Lambda }}^{*}$ interaction, whereas the clear peak signals survive only for the electroproduction, when we ignore the interaction. These different behaviors can be understood by different $Q^2$ dependencies in the $K^{*}$ electromagnetic and $K^{*}\to \gamma K$ transition form factors. We suggest a photon-polarization asymmetry $\mathrm{\Sigma }$ to extract information of the $K^{*}N{\mathrm{\Lambda }}^{*}$ interaction. It turns out that $\mathrm{\Sigma }$ near the ${\mathrm{\Lambda }}^{*}$ peak region becomes negative with a finite $K^{*}N{\mathrm{\Lambda }}^{*}$ interaction while positive without it for $Q^2=0$, because of the different naturalities of $K$ and $K^{*}$ exchanges. For $Q^2\ne 0$, we observe more obvious signals in the peak region owing to the additional contribution of the longitudinal virtual photon for ${\mathrm{\Lambda }}^{*}$.

Background: The ${}^{14}\mathrm{N}(p,\gamma ){}^{15}\mathrm{O}$ reaction plays a vital role in various astrophysical scenarios. Its reaction rate must be accurately known in the present era of high precision astrophysics. The cross section of the reaction is often measured relative to a low energy resonance, the strength of which must therefore be determined precisely.

Purpose: The activation method, based on the measurement of ${}^{15}\mathrm{O}$ decay, has not been used in modern measurements of the ${}^{14}\mathrm{N}(p,\gamma ){}^{15}\mathrm{O}$ reaction. The aim of the present work is to provide strength data for two resonances in the ${}^{14}\mathrm{N}(p,\gamma ){}^{15}\mathrm{O}$ reaction using the activation method. The obtained values are largely independent from previous data measured by in-beam $\gamma$ spectroscopy and are free from some of their systematic uncertainties.

Method: Solid state TiN targets were irradiated with a proton beam provided by the Tandetron accelerator of Atomki using a cyclic activation. The decay of the produced ${}^{15}\mathrm{O}$ isotopes was measured by detecting the 511 keV positron annihilation $\gamma$ rays.

Results: The strength of the ${\mathrm{E}}_p=278\mathrm{keV}$ resonance was measured to be $\omega {\gamma }_{278}=(13.4\pm 0.8)\mathrm{meV}$ while for the ${\mathrm{E}}_p=1058\mathrm{keV}$ resonance $\omega {\gamma }_{1058}=(442\pm 27)\mathrm{meV}$.

Conclusions: The obtained $E_p=278$ keV resonance strength is in fair agreement with the values recommended by two recent works. However, the $E_p=1058\mathrm{keV}$ resonance strength is about 20% higher than the previous value. The discrepancy may be caused in part by a previously neglected finite target thickness correction. As only the low energy resonance is used as a normalization point for cross section measurements, the calculated astrophysical reaction rate of the ${}^{14}\mathrm{N}(p,\gamma ){}^{15}\mathrm{O}$ reaction and therefore the astrophysical consequences are not changed by the present results.

We derive from the subleading contributions to the chiral three-nucleon (3N) force [long-range terms; published by V. Bernard et al., Phys. Rev. C 77, 064004 (2008)] a density-dependent two-nucleon interaction $V_{\text{med}}$ in isospin-symmetric, spin-saturated nuclear matter. Following the division of the pertinent 3N diagrams into two-pion-exchange topology, two-pion-one-pion–exchange topology, and ring topology, we evaluate for these all self-closings and concatenations of nucleon lines to an in-medium loop. The momentum and $k_f$-dependent potentials associated with the isospin operators (1 and ${\vec{\tau }}_1·{\vec{\tau }}_2$) and five independent spin structures are expressed in terms of functions which either are given in closed analytical form or require at most one numerical integration. In the same way we treat the $2\pi$-exchange 3N force at sub-subleading order. Our results for $V_{\text{med}}$ are most helpful to implement long-range subleading chiral 3N forces into nuclear many-body calculations.

High-spin states in the ${}^{73}\mathrm{Br}$ nucleus have been populated via the ${}^{50}\mathrm{Cr}({}^{28}\mathrm{Si},\alpha p){}^{73}\mathrm{Br}$ fusion evaporation reaction with a beam energy of 90 MeV. The deexciting gamma rays were detected using the Indian National Gamma Array (INGA). Using the $\gamma -\gamma$ coincidence technique, two new bands and eight new interconnecting transitions have been added. The strong interconnecting $E1$ transitions, between positive and negative parity bands, ensure the existence of octupole correlations at low spin. Line shapes have been observed for 17 transitions, which were analyzed by the Doppler-shift attenuation method to determine the lifetime of excited states of the yrast negative parity band and its signature partner band along with the positive parity band. The deduced transitional quadrupole moments $Q_t$ for the ground state band decrease with increasing spin, with their values ranging from 2.88 to 1.00 $e\mathrm{b}$. A similar trend in the quadrupole moment has also been observed for the signature partner as well as for the positive parity band. This decrease in $Q_t$ with increasing spin for these bands is interpreted in terms of the cranked Nilsson-Strutinsky model and total Routhian surface calculations, which indicate possible band termination at higher spin.

Employing a quantal diffusion description based on the stochastic mean-field approach, we analyze the mass distribution of the primary fragments in the collisions of the ${}^{136}\mathrm{Xe}+{}^{208}\mathrm{Pb}$ system at the bombarding energy $E_{\text{c.m.}}=526$ MeV. This quantal approach provides a good description of the primary fragment distribution without any adjustable parameter, including the effects of shell structure.