We construct a new Hartree-Fock-Bogoliubov (HFB) mass model, labeled HFB-18, with a generalized Skyrme force. The additional terms that we have introduced into the force are density-dependent generalizations of the usual $t_1$ and $t_2$ terms and are chosen in such a way as to avoid the high-density ferromagnetic instability of neutron stars that is a general feature of conventional Skyrme forces, and in particular of the Skyrme forces underlying all the HFB mass models that we have developed in the past. The remaining parameters of the model are then fitted to essentially all the available mass data, an rms deviation $\sigma$ of $0.585$ MeV being obtained. The new model thus gives almost as good a mass fit as our best-fit model HFB-17 ($\sigma =0.581$ MeV) and has the advantage of avoiding the ferromagnetic collapse of neutron stars.

In the present work we use the mean-field approximation to investigate quark matter described by the su(3) Nambu–Jona-Lasinio (NJL) model subject to a strong magnetic field. We consider two cases: pure quark matter and quark matter in $\beta$ equilibrium possibly present in magnetars. The results are compared with the ones obtained with the su(2) version of the model. The energy per baryon of magnetized quark matter becomes more bound than nuclear matter made of iron nuclei, for $B$ around $2\times {10}^{19}$ G. When the su(3) NJL model is applied to stellar matter, the maximum mass configurations are always above $1.45M_{\odot }$ and may be as high as $1.86M_{\odot }$ for a central magnetic field of $5\times {10}^{18}$ G. These numbers are within the masses of observed neutron stars.

The $\beta$-asymmetry parameter $\mathit{Ã}$ for the pure Gamow-Teller decay of ${}^{114}\mathrm{In}$ is reported. The low-temperature nuclear orientation method was combined with a GEANT4-based simulation code allowing us, for the first time, to address in detail the effects of scattering and the magnetic field. The result, $\mathit{Ã}=-0.994\pm 0.{010}_{\mathrm{stat}}\pm 0.{010}_{\mathrm{syst}}$, constitutes the most accurate value for the asymmetry parameter of a nuclear $\beta$ transition to date. The value is in agreement with the Standard Model prediction of $\mathit{Ã}=-1$ and provides new limits on tensor-type charged weak currents.

The structure of even-even $N=40$ isotones is studied from drip line to drip line through the systematic investigation of their quadrupole modes of excitation. Calculations are performed within the Hartree-Fock-Bogoliubov approach using the Gogny D1S effective interaction. Where relevant, these calculations are extended beyond mean field within a generator-coordinate-based method. An overall good agreement with available experimental data is reported, showing that collectivity increases from the neutron to the proton drip line. Whereas ${}^{60}\mathrm{Ca}$ and ${}^{68}\mathrm{Ni}$ display a calculated spherical shape in their ground states, all other isotones show a prolate-deformed ground-state band and a quasi-$\gamma$ band. Coexistence features are predicted in the neutron-deficient $N=40$ isotones above ${}^{74}\mathrm{Se}$.

We have measured the $K$-shell internal conversion coefficient, ${\alpha }_K$, for the $346.5$-keV $M4$ transition in ${}^{197}\mathrm{Pt}$ to be $4.23(7)$. This result differs from a previous value, which disagreed significantly from theory. Our new value agrees well with Dirac-Fock calculations and removes the earlier discrepancy as a source of concern.

The cross sections and angular correlations for neutron decay into various states in the residual nucleus following the ${}^{10}\mathrm{B}$($e,e^{\text{'}}n$) reaction have been measured over the excitation energy range of 18–33 MeV at an effective momentum transfer of 0.56 fm${}^{-1}$. In the giant resonance, neutron emission leads to the population of two higher excited states in addition to the ground-state transition: 6.97 MeV $7/2^{-}(n_5$) and 11.70 MeV $7/2^{-}+12.06$ MeV $3/2^{-}(n_{6,7}$). This is the first observation of the neutron population of these states. The angular correlations for $n_0$ show a strong forward-backward asymmetry, which suggests interference from a transition with the opposite parity to $E1$. The angular correlations for $n_5$ and $n_{6,7}$ have a peak shift of about ${50}^{°}$ at lower excitation energy and recover above about 24 and 25 MeV for $n_5$ and $n_{6,7}$, respectively. Their patterns are considerably different from that for $n_0$. The angular correlations for each transition were fitted with a Legendre polynomial. The longitudinal-transverse interference coefficient $C_2/A_0$ is negligible for all populations. For $n_0$ decay, all Legendre coefficients $b_i$ are positive, but $b_2$ and $b_3$ for the $n_5$ and $n_{6,7}$ decays are negative at lower excitation energy, and the latter causes a shift of the forward peak. The negative values may come from the signs of the phase differences of $\cos {\delta }_{21}$ and $\cos {\delta }_{20}$. The ${}^{10}\mathrm{B}$($e,e^{\text{'}}n$) cross section measured up to $E_x~32$ MeV agrees well with that of ${}^{10}\mathrm{B}$($\gamma ,n$), except for a peak at 23 MeV of the giant resonance. In comparison with shell-model calculations, the partial cross section for $n_0$ is sizable up to higher excitation energy, and predicted large partial cross sections populating the 6.97 MeV $7/2^{-}$ and 11.70 MeV $7/2^{-}+12.06$ MeV $3/2^{-}$ states in the giant resonance were not observed.

Elastic-scattering angular distributions for the ${}^6\mathrm{Li}+{}^{64}\mathrm{Zn}$ system were measured at eight beam energies from below to above the Coulomb barrier, $12.0⩽E_{\mathrm{lab}}⩽22.0$ MeV. The experimental data were analyzed within the optical model to study the energy dependence of the interaction potential and to obtain total reaction cross sections. The results obtained using several optical model potentials show similar behavior. The energy dependence of the strengths of the real and imaginary potentials suggests the presence of the breakup threshold anomaly. It is shown that the extracted energy dependence of the interaction potential at sub-barrier energies is very sensitive to possible experimental errors.

Within a dynamical coupled-channels model that has already been fixed by analyzing the data of the $\pi N\to \pi N$ and $\gamma N\to \pi N$ reactions, we present the predicted double pion photoproduction cross sections up to the second resonance region, $W<1.7$ GeV. The roles played by the different mechanisms within our model in determining both the single and double pion photoproduction reactions are analyzed, focusing on the effects attributable to the direct $\gamma N\to \pi \pi N$ mechanism, the interplay between the resonant and nonresonant amplitudes, and the coupled-channels effects. The model parameters that can be determined most effectively in the combined studies of both the single and double pion photoproduction data are identified for future studies.

The nuclear structure of neutron-rich $N>126$ nuclei has been investigated following their production via relativistic projectile fragmentation of a $E/A=1$ GeV ${}^{238}\mathrm{U}$ beam. Metastable states in the $N=128$ isotones ${}^{208}\mathrm{Hg}$ and ${}^{209}\mathrm{Tl}$ have been identified. Delayed $\gamma$-ray transitions are interpreted as arising from the decay of $I^{\pi }=(8^{+})$ and ($17/2^{+}$) isomers, respectively. The data allow for the so far most comprehensive verification of the shell-model approach in the region determined by magic numbers $Z<82$ and $N>126$.

The two recent density-dependent versions of the finite-range M3Y interaction (CDM3Y$n$ and M3Y-P$n$) have been probed against the bulk properties of asymmetric nuclear matter (NM) in the nonrelativistic Hartree-Fock (HF) formalism. The same HF study has also been done with the famous Skyrme (SLy4) and Gogny (D1S and D1N) interactions that were well tested in the nuclear structure calculations. Our HF results are compared with those given by other many-body calculations like the Dirac-Brueckner Hartree-Fock approach or ab initio variational calculations using free nucleon-nucleon interaction and by both the nonrelativistic and relativistic mean-field studies using different model parameters. Although the two considered density-dependent versions of the M3Y interaction were proven to be quite realistic in the nuclear structure or reaction studies, they give two distinct behaviors of the NM symmetry energy at high densities, like the Asy-soft and Asy-stiff scenarios found earlier with other mean-field interactions. As a consequence, we obtain two different behaviors of the proton fraction in the $\beta$-equilibrium that in turn can imply two drastically different mechanisms for the neutron star cooling. While some preference of the Asy-stiff scenario was found based on predictions of the latest microscopic many-body calculations or empirical NM pressure and isospin diffusion data deduced from heavy-ion collisions, a consistent mean-field description of nuclear structure database is more often given by some Asy-soft type interaction like the Gogny or M3Y-P$n$ ones. Such a dilemma poses an interesting challenge to the modern mean-field approaches.

Three-nucleon scattering equations with irreducible three-nucleon force are solved in momentum-space. The Coulomb interaction between the two protons is included using the method of screening and renormalization. The need for the renormalization of the scattering amplitudes is demonstrated numerically. The Coulomb and Urbana IX three-nucleon force effects on the observables of elastic proton-deuteron scattering and breakup are studied.

Pairing (particle-particle) giant resonances are analyzed within a shell-model formalism in the complex energy plane with the aim of understanding why they have not been observed so far. A comparison is made with the equivalent particle-hole mode by applying the formalism to the analysis of the well-understood particle-hole giant resonance. It is found that because of the proper treatment of the continuum intrinsic to the formalism, giant pairing resonances lie much higher than previously predicted and that some of them may be too wide to be observed, whereas others are meaningful excitations. For these, new experimental searches are proposed.

The quantitative dependence of quark-gluon plasma (QGP)-formation probability ($P_{\mathrm{QGP}}$) on the centrality of $\mathrm{Au}-\mathrm{Au}$ collisions is studied using a bond percolation model. The $P_{\mathrm{QGP}}$ versus the maximum distance $S_{\max }$ for a bond to form is calculated from the model for various nuclei and the $P_{\mathrm{QGP}}$ at different centralities of $\mathrm{Au}-\mathrm{Au}$ collisions for the given $S_{\max }$ are obtained therefrom. The experimental data of the nuclear modification factor $R_{\mathit{AA}}(p_T)$ for the most central $\mathrm{Au}-\mathrm{Au}$ collisions at $\sqrt{s_{\mathit{NN}}}=200$ and $130$ GeV are utilized to transform $S_{\max }$ to $\sqrt{s_{\mathit{NN}}}$. The $P_{\mathrm{QGP}}$ for different centralities of $\mathrm{Au}-\mathrm{Au}$ collisions at these two energies are thus obtained, which is useful for correctly understanding the centrality dependence of the experimental data.

Neutron star properties, such as mass, radius, and moment of inertia, are calculated by solving the Tolman-Oppenheimer-Volkov (TOV) equations using the ring-diagram equation of state (EOS) obtained from realistic low-momentum $\mathit{NN}$ interactions $V_{\mathrm{low}–\mathrm{k}}$. Several $\mathit{NN}$ potentials (CDBonn, Nijmegen, Argonne V18, and BonnA) have been employed to calculate the ring-diagram EOS where the particle-particle hole-hole ring diagrams are summed to all orders. The proton fractions for different radial regions of a $\beta$-stable neutron star are determined from the chemical potential conditions ${\mu }_n-{\mu }_p={\mu }_e={\mu }_{\mu }$. The neutron star masses, radii, and moments of inertia given by the aforementioned potentials all tend to be too small compared with the accepted values. Our results are largely improved with the inclusion of a Skyrme-type three-body force based on Brown-Rho scalings where the in-medium meson masses, particularly those of $\omega$, $\rho$, and $\sigma$, are slightly decreased compared with their in-vacuum values. Representative results using such medium-corrected interactions are maximum neutron-star mass $M~1.8M_{\odot }$ with radius $R~9$ km and moment of inertia $~60M_{\odot }\hspace{0.5em}{\mathrm{km}}^2$, values given by the four $\mathit{NN}$ potentials being nearly the same. The effects of nuclei-crust EOSs on the properties of neutron stars are discussed.

It has been shown that the thermal photon and the lepton pair spectra can be used to estimate the radial velocity of different phases of the matter formed in nuclear collisions at ultrarelativistic energies. We observe a nonmonotonic variation of the flow velocity with invariant mass of the lepton pair, which is indicative of two different thermal dilepton sources at early and late stages of the dynamically evolving system. We also show that the study of radial velocity through electromagnetic probes may shed light on the nature of the phase transition from hadrons to a quark-gluon plasma.

The formation and evolution of the elliptic flow pattern in $\mathrm{Pb}+\mathrm{Pb}$ collisions at $\sqrt{s}=5.5A$ TeV and in $\mathrm{Au}+\mathrm{Au}$ collisions at $\sqrt{s}=200A$ GeV are analyzed for different hadron species within the framework of the HYDJET$++$ Monte Carlo model. The model contains both hydrodynamic state and jets, thus allowing for a study of the interplay between the soft and hard processes. It is found that jets terminate the rise of the elliptic flow with increasing transverse momentum. Since jets are more influential at the Large Hadron Collider (LHC) than at the Relativistic Heavy Ion Collider (RHIC), the elliptic flow at LHC should be weaker than that at RHIC. The influence of resonance decays on particle elliptic flow is also investigated. These final state interactions enhance the low-$p_T$ part of the $v_2$ of pions and light baryons and work toward the fulfillment of idealized constituent quark scaling.

Microscopic signatures of nuclear ground-state shape phase transitions in Nd isotopes are studied using excitation spectra and collective wave functions obtained by diagonalization of a five-dimensional Hamiltonian for quadrupole vibrational and rotational degrees of freedom, with parameters determined by constrained self-consistent relativistic mean-field calculations for triaxial shapes. As a function of the physical control parameter, the number of nucleons, energy gaps between the ground state and the excited vibrational states with zero angular momentum, isomer shifts, and monopole transition strengths exhibit sharp discontinuities at neutron number $N=90$, which is characteristic of a first-order quantum phase transition.

The very neutron deficient odd-odd nucleus ${}^{172}\mathrm{Au}$ was studied in reactions of 342 and 348 MeV ${}^{78}\mathrm{Kr}$ beams with an isotopically enriched ${}^{96}\mathrm{Ru}$ target. The $\alpha$ decays previously reported for ${}^{172}\mathrm{Au}$ were confirmed and the decay chain extended down to ${}^{152}\mathrm{Tm}$ through the discovery of a new $\alpha$-decaying state in ${}^{164}\mathrm{Re}$ [$E_{\alpha }=5623(10)$ keV; $t_{1/2}={864}_{-110}^{+150}$ ms; $b_{\alpha }=3(1)\%$]. Fine structure in these $\alpha$ decays of ${}^{172}\mathrm{Au}$ and ${}^{168}\mathrm{Ir}$ were identified. A new $\alpha$-decaying state was also observed and assigned as the ground state in ${}^{172}\mathrm{Au}$ [$E_{\alpha }=6762(10)$ keV; $t_{1/2}={22}_{-5}^{+6}$ ms]. This decay chain was also correlated down to ${}^{152}\mathrm{Tm}$ through previously reported $\alpha$ decays. Prompt $\gamma$ rays from excited states in ${}^{172}\mathrm{Au}$ have been identified using the recoil-decay tagging technique. The partial level scheme constructed for ${}^{172}\mathrm{Au}$ indicates that it has an irregular structure. Possible configurations of the $\alpha$-decaying states in ${}^{172}\mathrm{Au}$ are discussed in terms of the systematics of nuclei in this region and total Routhian surface calculations.

We study the couplings between collective vibrations such as the isovector giant dipole and isoscalar giant quadrupole resonances in tin isotopes in the framework of the time-dependent Hartree-Fock theory with a Skyrme energy density functional. These couplings are a source of anharmonicity in the multiphonon spectrum. In particular, the residual interaction is known to couple the isovector giant dipole resonance with the isoscalar giant quadrupole resonance built on top of it, inducing a nonlinear evolution of the quadrupole moment after a dipole boost. This coupling also affects the dipole motion in a nucleus with a static or dynamical deformation induced by a quadrupole constraint or boost, respectively. Three methods associated with these different manifestations of the coupling are proposed to extract the corresponding matrix elements of the residual interaction. Numerical applications of the different methods to ${}^{132}\mathrm{Sn}$ are in good agreement with each other. Finally, several tin isotopes are considered to investigate the role of isospin and mass number on this coupling. A simple $1/A$ dependence of the residual matrix elements is found with no noticeable contribution from the isospin. This result is interpreted within the Goldhaber-Teller model.

Using viscous relativistic hydrodynamics we show that systematic studies of the impact parameter dependence of the eccentricity-scaled elliptic flow $v_2/\varepsilon$ can distinguish between different models for the calculation of the initial source eccentricity $\varepsilon$. This removes the largest present uncertainty in the extraction of the specific viscosity of the matter created in relativistic heavy-ion collisions from precise elliptic-flow measurements.