Background: Nuclear reactions are complex, involving collisions between composite systems where many-body dynamics determines outcomes. Successful models have been developed to explain particular reaction outcomes in distinct energy and mass regimes, but a unifying picture remains elusive. The irreversible transfer of kinetic energy from the relative motion of the collision partners to their internal states, as is known to occur in deep inelastic collisions, has yet to be successfully incorporated explicitly into fully quantal reaction models. The influence of these processes on fusion is not yet quantitatively understood.

Purpose: To investigate the population of high excitation energies in transfer reactions at sub-barrier energies, which are precursors to deep inelastic processes, and their dependence on the internuclear separation.

Methods: Transfer probabilities and excitation energy spectra have been measured in collisions of ${}^{16,18}\mathrm{O},{}^{19}\mathrm{F}+{}^{208}\mathrm{Pb}$, at various energies below and around the fusion barrier, by detecting the backscattered projectile-like fragments in a $\mathrm{\Delta }E\text{−}E$ telescope.

Results: The relative yields of different transfer outcomes are strongly driven by $Q$ values, but change with the internuclear separation. In ${}^{16}\mathrm{O}+{}^{208}\mathrm{Pb}$, single nucleon transfer dominates, with a strong contribution from $-2p$ transfer close to the Coulomb barrier, though this channel becomes less significant in relation to the $-2p2n$ transfer channel at larger separations. For ${}^{18}\mathrm{O}+{}^{208}\mathrm{Pb}$, the $-2p2n$ channel is the dominant charge transfer mode at all separations. In the reactions with ${}^{19}\mathrm{F},-3p2n$ transfer is significant close to the barrier, but falls off rapidly with energy. Multinucleon transfer processes are shown to lead to high excitation energies (up to $\sim 15$ MeV), which is distinct from single nucleon transfer modes which predominantly populate states at low excitation energy.

Conclusions: Kinetic energy is transferred into internal excitations following transfer, with this energy being distributed over a larger number of states and to higher excitations with increasing numbers of transferred nucleons. Multinucleon transfer is thus a mechanism by which energy can be dissipated from the relative motion before reaching the fusion barrier radius.

We considered three different nucleon-nucleon (NN) elastic differential cross sections: the Cugnon et al. parameterized differential cross section [Nucl. Instrum. Methods Phys. Res., Sect. B 111, 215 (1996)], the differential cross section derived from the collision term of the self-consistent relativistic Boltzmann-Uehling-Uhlenbeck equation proposed by Mao et al. [Z. Phys. A 347, 173 (1994)], and the isotropic differential cross section within the newly updated version of the ultrarelativistic quantum molecular dynamics (UrQMD) model. By doing so, we investigated the influence of the differential elastic NN cross section on various observables (e.g., nuclear stopping, both the rapidity and transverse-velocity dependence of the directed and elliptic flows) in Au+Au collisions at beam energies 150, 250, 400, and $800\mathrm{MeV}/\mathrm{nucleon}$. By comparing calculations with those three differential cross sections, we found that the nuclear stopping power and the directed and elliptic flows are affected to some extent by the differential cross sections, and the impact of differential cross section on those observables becomes more visible as the beam energy increases. The effect on the elliptic flow difference $v_2^n\text{−}{v}_2^H$ and ratio $v_2^n/v_2^H$ of neutrons versus hydrogen isotopes $\left(Z=1\right)$, which have been used as sensitive observables for probing nuclear symmetry energy at high densities, is weak.

Strong magnetic fields have important effects on the crustal properties of magnetars. Here we study the magnetoelastic oscillations of magnetars, taking into consideration the effect of strong magnetic fields on the crustal composition (magnetized crust). We calculate global magnetoelastic (GME) modes as well as modes confined to the crust (CME) only. The ideal magnetohydrodynamics is adopted for the calculation of magnetoelastic oscillations of magnetars with dipole magnetic fields. The perturbation equations obtained in general relativity using Cowling approximation are exploited here for the study of magnetoelastic oscillations. Furthermore, deformations due to magnetic fields and rotations are neglected in the construction of equilibrium models for magnetars. The composition of the crust directly affects its shear modulus, which we calculate using three different nucleon-nucleon interactions: SLy4, SkM, and Sk272. The shear modulus of the crust is found to be enhanced in strong magnetic fields $\ge {10}^{17}$ G for all those Skyrme interactions. It is noted that the shear modulus of the crust for the SLy4 interaction is much higher than those of the SkM and Sk272 interactions in presence of magnetic fields or not. Though we do not find any appreciable change in frequencies of fundamental GME and CME modes with and without magnetized crusts, frequencies of first overtones of CME modes are significantly affected in strong magnetic fields $\ge {10}^{17}$ G. However, this feature is not observed in frequencies of first overtones of GME modes. As in earlier studies, it is also noted that the effects of crusts on frequencies of both types of magnetoelastic modes disappear when the magnetic field reaches the critical field ($B>4\times {10}^{15}$ G). Frequencies of GME and CME modes calculated with magnetized crusts based on all three nucleon-nucleon interactions, stellar models and magnetic fields, are compared with frequencies of observed quasiperiodic oscillations (QPOs) in SGR 1806-20 and SGR1900+14. As in earlier studies, this comparison indicates that GME modes are essential to explain all the frequencies, as CME modes can explain only the higher frequencies.

We apply the large-$N_c$ expansion to the time-reversal-invariance-violating (TV) nucleon-nucleon potential. The operator structures contributing to next-to-next-to-leading order in the large-$N_c$ counting are constructed. For the TV and parity-violating case we find a single operator structure at leading order. The TV but parity-conserving potential contains two leading-order terms, which, however, are suppressed by $1/N_c$ compared to the parity-violating potential. Comparison with phenomenological potentials, including the chiral effective field theory potential in the TV parity-violating case, leads to large-$N_c$ scaling relations for TV meson-nucleon and nucleon-nucleon couplings.

In this paper we study odd-even staggering phenomena of binding energy in the framework of the nuclear shell model for nuclei in the $sd$ shell. We decompose the USDB effective interaction into the monopole interaction and multipole (residual) interactions. We extract the empirical proton-neutron interaction, the Wigner energy, and the one-neutron separation energy using calculated binding energies. The monopole interaction, which represents the spherical mean field, provides contributions to the empirical proton-neutron interaction, the symmetry energy, and the Wigner energy. It does not induce odd-even staggering of the empirical proton-neutron interaction or the one-neutron separation energy. Isovector monopole and quadrupole pairing interactions and isoscalar spin-1 pairing interactions play a key role in reproducing an additional binding energy in both even-even and odd-odd nuclei. The Wigner energy coefficients are sensitive to residual two-body interactions. The nuclear shell structure has a strong influence on the evolution of the one-neutron separation energy, but not on empirical proton-neutron interactions. The so-called three-point formula is a good probe of the shell structure.

The level structures of ${}^{130,132}\text{Xe}$ were studied with the inelastic neutron scattering reaction followed by $\gamma$-ray detection. Level lifetimes were measured using the Doppler-shift attenuation method and low-lying excited states in these nuclei were characterized. With a focus on the decay properties of the $0^{+}$ states, these nuclei were examined as representations of the E(5) critical-point symmetry.

Background: ${}^{34}\mathrm{Na}$ is conjectured to play an important role in the production of seed nuclei in the alternate $r$-process paths involving light neutron rich nuclei very near the $\beta$-stability line, and as such, it is important to know its ground state properties and structure to calculate rates of the reactions it might be involved in, in the stellar plasma. Found in the region of ‘island of inversion’, its ground state might not be in agreement with normal shell model predictions.

Purpose: The aim of this paper is to study the elastic Coulomb breakup of ${}^{34}\mathrm{Na}$ on ${}^{208}\mathrm{Pb}$ to give us a core of ${}^{33}\mathrm{Na}$ with a neutron and in the process we try and investigate the one neutron separation energy and the ground state configuration of ${}^{34}\mathrm{Na}$.

Method: A fully quantum mechanical Coulomb breakup theory within the architecture of post-form finite range distorted wave Born approximation extended to include the effects of deformation is used to research the elastic Coulomb breakup of ${}^{34}\mathrm{Na}$ on ${}^{208}\mathrm{Pb}$ at 100 MeV/u. The triple differential cross section calculated for the breakup is integrated over the desired components to find the total cross-section, momentum, and angular distributions as well as the average momenta, along with the energy-angular distributions.

Results: The total one neutron removal cross section is calculated to test the possible ground state configurations of ${}^{34}\mathrm{Na}$. The average momentum results along with energy-angular calculations indicate ${}^{34}\mathrm{Na}$ to have a halo structure. The parallel momentum distributions with narrow full widths at half-maxima signify the same.

Conclusion: We have attempted to analyze the possible ground state configurations of ${}^{34}\mathrm{Na}$ and in congruity with the patterns in the ‘island of inversion’ conclude that even without deformation, ${}^{34}\mathrm{Na}$ should be a neutron halo with a predominant contribution to its ground state most probably coming from ${}^{33}\mathrm{Na}(3/2^{+})\otimes$ $2p_{3/2}\nu$ configuration. We also surmise that it would certainly be useful and rewarding to test our predictions with an experiment to put stricter limits on its ground state configuration and binding energy.

Momentum-space azimuthal harmonic event planes (EP) are constructed from final-state midrapidity particles binned in transverse momentum $\left(p_T\right)$ in $\sqrt{s_{NN}}=200$ GeV Au+Au collisions in a multiphase transport (AMPT) model. The EP correlations between $p_T$ bins, corrected by EP resolutions, are smaller than unity. This indicates that the EP's decorrelate over $p_T$ in AMPT, qualitatively consistent with data and hydrodynamic calculations. It is further found that the EP correlations approximately factorize into single $p_T$-bin EP correlations to a common plane. This common plane appears to be the momentum-space EP integrated over all $p_T$, not the configuration-space participant plane (PP).

Partonic matter produced in the early stage of ultrarelativistic nucleus-nucleus collisions is assumed to be composed mainly of gluons, and quarks and antiquarks are produced at later times. To study the implications of such a scenario, the dynamical evolution of a chemically nonequilibrated system is described by ideal (2+1)-dimensional hydrodynamics with a time dependent (anti)quark fugacity. The equation of state interpolates linearly between the lattice data for the pure gluonic matter and the lattice data for the chemically equilibrated quark-gluon plasma. The spectra and elliptic flows of thermal dileptons and photons are calculated for central Pb+Pb collisions at the CERN Large Hadron Collider energy of $\sqrt{s_{NN}}=2.76$ TeV. We test the sensitivity of the results to the choice of equilibration time, including also the case where the complete chemical equilibrium of partons is reached already at the initial stage. It is shown that a suppression of quarks at early times leads to a significant reduction of the yield of the thermal dileptons, but only to a rather modest suppression of the $p_T$ distribution of direct photons. It is demonstrated that an enhancement of photon and dilepton elliptic flows might serve as a promising signature of the pure-glue initial state.

Background: Synthesis of superheavy elements (SHEs) with fusion-evaporation reactions is strongly hindered by the quasifission (QF) mechanism which prevents the formation of an equilibrated compound nucleus and which depends on the structure of the reactants. New SHEs have been recently produced with doubly-magic ${}^{48}\mathrm{Ca}$ beams. However, SHE synthesis experiments with single-magic ${}^{50}\mathrm{Ti}$ beams have so far been unsuccessful.

Purpose: In connection with experimental searches for $Z=117,119$ superheavy elements, we perform a theoretical study of fusion and quasifission mechanisms in ${}^{48}\mathrm{Ca},{}^{50}\mathrm{Ti}+{}^{249}\mathrm{Bk}$ reactions in order to investigate possible differences in reaction mechanisms induced by these two projectiles.

Methods: The collision dynamics and the outcome of the reactions are studied using unrestricted time-dependent Hartree-Fock (TDHF) calculations as well as the density-constrained TDHF method to extract the nucleus-nucleus potentials and the excitation energy in each fragment.

Results: Nucleus-nucleus potentials, nuclear contact times, masses and charges of the fragments, as well as their kinetic and excitation energies strongly depend on the orientation of the prolate ${}^{249}\mathrm{Bk}$ nucleus. Long contact times associated with fusion are observed in collisions of both projectiles with the side of the ${}^{249}\mathrm{Bk}$ nucleus, but not on collisions with its tip. The energy and impact parameter dependencies of the fragment properties, as well as their mass-angle and mass–total kinetic energy correlations are investigated.

Conclusions: Entrance channel reaction dynamics are similar with both ${}^{48}\mathrm{Ca}$ and ${}^{50}\mathrm{Ti}$ projectiles. Both are expected to lead to the formation of a compound nucleus by fusion if they have enough energy to get in contact with the side of the ${}^{249}\mathrm{Bk}$ target.

Nuclear dissipation retards fission. Using the stochastic Langevin model, we calculate the drop of fission cross section caused by friction over its standard statistical-model value, ${\sigma }_f^{\mathrm{drop}}$, as a function of the presaddle friction strength for fissioning nuclei ${}^{195}\mathrm{Bi}, {}^{202}\mathrm{Bi}$, and ${}^{209}\mathrm{Bi}$ as well as for different angular momenta. We find that friction effects on ${\sigma }_f^{\mathrm{drop}}$ are substantially enhanced with increasing isospin of the Bi system and become greater with decreasing angular momentum. Our findings suggest that in experiments, to better constrain the strength of presaddle dissipation through the measurement of fission excitation functions, it is optimal to yield those compound systems with a high isospin and a low spin. Furthermore, we analyze the data of fission excitation functions of ${}^{210}\mathrm{Po}$ and ${}^{209}\mathrm{Bi}$ systems, which are populated in $p+{}^{209}\mathrm{Bi}$ and $p+{}^{208}\mathrm{Pb}$ reactions and which have a high isospin and a low spin, and find that Langevin calculations with a presaddle friction strength of (3–5) $\times {10}^{-21}$ ${\mathrm{s}}^{-1}$ describe these experimental fission data very well.

$\beta$ decay of neutron-rich nuclide ${}^{94}\mathrm{Kr}$ was reinvestigated by means of a high resolution on-line mass separator and $\beta -\gamma$ spectroscopy. In total 22 $\gamma$-ray transitions were assigned to the decay of ${}^{94}\mathrm{Kr}$, and a new isomeric state was identified. The new information allows us to build detailed levels systematics in a chain of odd-odd rubidium isotopes and draw conclusions on nuclear structure for some of the observed states. The discussed level structure affects the evolution of $\beta$-decay half-lives for neutron-rich selenium, krypton, and strontium isotopes.

The isoscalar giant quadrupole resonance in ${}^{28}\mathrm{Si}$ and ${}^{27}\mathrm{Al}$ has been investigated with high-energy-resolution proton inelastic scattering at $E_{\mathrm{p}}=200\mathrm{MeV}$ and at scattering angles close to the maximum of $\mathrm{\Delta }L=2$ angular distributions with the K600 magnetic spectrometer of iThemba LABS, South Africa. Characteristic scales are extracted from the observed fine structure with a wavelet analysis and compared for ${}^{28}\mathrm{Si}$ with random-phase approximation and second random phase approximation calculations with an interaction derived from the Argonne V18 potential by a unitary transformation. A recent extension of the method to deformed nuclei provides the best description of the data, suggesting the significance of Landau damping.

The ground state phase transition in Nd, Sm, and Gd isotopes is investigated by using the Nilsson mean-field plus standard pairing model based on the exact solutions obtained from the extended Heine-Stieltjes correspondence. The results of the model calculations successfully reproduce the critical phenomena observed experimentally in the odd-even mass differences, odd-even differences of two-neutron separation energy, and the $\alpha$-decay and double ${\beta }^{-}$-decay energies of these isotopes. Since the odd-even effects are the most important signatures of pairing interactions in nuclei, the model calculations yield microscopic insight into the nature of the ground state phase transition manifested by the standard pairing interaction.

The collective nature of high-spin yrast states in even-even ${}^{160-190}\mathrm{W}$ isotopes was systematically investigated by means of pairing self-consistent Woods-Saxon-Strutinsky calculations using the total Routhian surface approach in $({\beta }_2,\gamma ,{\beta }_4)$ deformation space. The calculated ground-state deformations are consistent with previous calculations and available experimental data. The deformation energy curves are presented to show the shape and softness evolutions, in particular in the triaxial direction. The backbending or upbending behavior in moment of inertia is attributed to band crossing. It is found that the neutron rotation alignment is preferred for most of the W isotopes (e.g., in ${}^{164-180}\mathrm{W}$), while in other nuclei the competition between the neutron and proton alignments may occur, even the proton alignment is favored in the very neutron-deficient nucleus ${}^{160}\mathrm{W}$. In addition, the evolution and transition between vibrational and rotational collective modes along the yrast line are investigated on the basis of the new centipedelike E-GOS (E-Gamma Over Spin) curves introduced by us, which to some extent explains the existing differences (e.g., in the moment of inertia) between theory and experiment.

The high-spin states in ${}^{153}\text{Ho}$ have been studied by the ${}_{57}{}^{139}\text{La}({}^{20}\text{Ne},6n)$ reaction at a projectile energy of 139 MeV at the Variable Energy Cyclotron Centre (VECC), Kolkata, India, utilizing an earlier campaign of the Indian National Gamma Array (INGA) setup. Data from $\gamma -\gamma$ coincidence, directional correlation, and polarization measurements have been analyzed to assign and confirm the spins and parities of the levels. We have suggested a few additions and revisions of the reported level scheme of ${}^{153}\text{Ho}$. The RF-$\gamma$ time difference spectra have been useful to confirm the half-life of an isomer in this nucleus. From the comparison of experimental and theoretical results, it is found that there are definite indications of shape coexistence in this nucleus. The experimental and calculated lifetimes of several isomers have been compared to follow the coexistence and evolution of shape with increasing spin.

The scaling of photoproduction $\gamma p\to {\pi }^{0}p$ is investigated in the Reggeized model with $N^{*}$ and $\mathrm{\Delta }$ resonances included to describe resonance peaks up to photon energy $E_{\gamma }=3\mathrm{GeV}$. Given the $t$-channel exchanges $\rho \left(770\right)+\omega \left(780\right)+b_1\left(1235\right)+h_1\left(1170\right)$ Reggeized for the background contribution, the resonances of the Breit-Wigner form are introduced to agree with cross sections for total, differential, and beam asymmetry in the low energy region. The scaled differential cross sections $s^{7}d\sigma /dt$ are reproduced to agree with the recent JLab data, revealing the production mechanism of the big bump structure around $W\approx 2.2$ GeV by the deep-dip pattern of the $\omega$ exchange that originates from the zeros of the trajectory ${\alpha }_{\omega }\left(t\right)=0$ in the canonical phase, $\frac{1}{2}(-1+e^{-i\pi {\alpha }_{\omega }\left(t\right)})$.

Possibilities of observing a signal of an ${\eta }^{\prime }n$ bound state are investigated by considering photoproductions of the $\eta$ and ${\eta }^{\prime }$ mesons on a deuteron target with forward proton emission. For this purpose, we take the ${\eta }^{\prime }n$ interaction from the linear $\sigma$ model with a coupling to $\eta n$, in which an $s\text{-wave} {\eta }^{\prime }n$ bound state can be dynamically generated, and we fix the $\gamma p\to \eta p$ and ${\eta }^{\prime }p$ scattering amplitudes so as to reproduce the experimental cross sections with forward proton emission. By using these $\gamma p\to {\eta }^{(\prime )}p$ and ${\eta }^{(\prime )}n\to {\eta }^{(\prime )}n$ amplitudes, we calculate cross sections of the $\gamma d\to \eta np$ and ${\eta }^{\prime }np$ reactions with forward proton emission in single and ${\eta }^{(\prime )}\text{-exchange}$ double-scattering processes. As a result, we find that the signal of the ${\eta }^{\prime }n$ bound state can be seen below the ${\eta }^{\prime }n$ threshold in the $\eta n$ invariant mass spectrum of the $\gamma d\to \eta np$ reaction and is comparable with the contribution from the quasifree ${\eta }^{\prime }$ production above the ${\eta }^{\prime }n$ threshold. We also discuss the behavior of the signal of the ${\eta }^{\prime }n$ bound state in several experimental conditions and model parameters.

Background: Single-reference density functional theory is very successful in reproducing bulk nuclear properties like binding energies, radii, or quadrupole moments throughout the entire periodic table. Its extension to the multireference level allows for restoring symmetries and, in turn, for calculating transition rates.

Purpose: We propose a new variant of the no-core-configuration-interaction (NCCI) model treating properly isospin and rotational symmetries. The model is applicable to any nucleus irrespective of its mass and neutron- and proton-number parity. It properly includes polarization effects caused by an interplay between the long- and short-range forces acting in the atomic nucleus.

Methods: The method is based on solving the Hill-Wheeler-Griffin equation within a model space built of linearly dependent states having good angular momentum and properly treated isobaric spin. The states are generated by means of the isospin and angular-momentum projection applied to a set of low-lying (multi)particle-(multi)hole deformed Slater determinants calculated using the self-consistent Skyrme-Hartree-Fock approach.

Results: The theory is applied to calculate energy spectra in $N\approx Z$ nuclei that are relevant from the point of view of a study of superallowed Fermi $\beta$ decays. In particular, a new set of the isospin-symmetry-breaking corrections to these decays is given.

Conclusions: It is demonstrated that the NCCI model is capable of capturing main features of low-lying energy spectra in light and medium-mass nuclei using relatively small model space and without any local readjustment of its low-energy coupling constants. Its flexibility and a range of applicability makes it an interesting alternative to the conventional nuclear shell model.

In this paper we study low-lying states of five $N=82$ isotones, ${}^{134}\mathrm{Te}, {}^{136}\mathrm{Xe}, {}^{138}\mathrm{Ba}, {}^{140}\mathrm{Ce}$ and ${}^{142}\mathrm{Nd}$, within the framework of the nucleon-pair approximation (NPA). For the low-lying yrast states of ${}^{136}\mathrm{Xe}$ and ${}^{138}\mathrm{Ba}$, we calculate the overlaps between the wave functions obtained in the full shell-model (SM) space and those obtained in the truncated NPA space, and find that most of these overlaps are very close to 1. Very interestingly and surprisingly, for most of these yrast states, the SM wave functions are found to be well approximated by one-dimensional, optimized pair basis states, which indicates a simple picture of “nucleon-pair states”. The positive-parity yrast states with spin $J>6$ in these nuclei, as well as the $8_2^{+}$ state, are found to be well described by breaking one or two $S$ pair(s) of the $6_1^{+}$ or $6_2^{+}$ state (low-lying, seniority-two, spin-maximum, and positive-parity); similarly, negative-parity yrast states with spin $J>9$ are well represented by breaking one or two $S$ pair(s) of the $9_1^{-}$ state (low-lying, seniority-two, spin-maximum, and negative-parity). It is shown that the low-lying negative-parity yrast states of ${}^{136}\mathrm{Xe}$ and ${}^{138}\mathrm{Ba}$ are reasonably described to be one-octupole-phonon excited states. The evolution of the $6_1^{+}$ and $6_2^{+}$ states for the five isotones are also systematically investigated.