For two neutrons and two protons or two neutron holes and two proton holes in a single $j$-shell, the state $|\varphi \rangle$ with isospin and seniority zero and the lowest angular momentum zero state $|\chi \rangle$ produced by an attractive interaction of quasinucleon pairs with angular momentum $2j$ have a large overlap for all relevant $j$ and large contents of quasinucleon pairs with angular momenta $2j$ and 0, respectively. In the $1f_{7/2}$ and $1g_{9/2}$ shells, the large negative matrix elements of the effective interaction in these two channels relative to most of the rest therefore cooperate to produce a ground state which is essentially a linear combination of $|\varphi \rangle$ and $|\chi \rangle$ with comparable coefficients. Interaction matrix elements in other channels influence significantly the ratio of these coefficients. The state $|\varphi \rangle$ makes up about 80% of the calculated ground states. The overlaps of the latter with $|\chi \rangle$ are less in the $1g_{9/2}$ shell than in the $1f_{7/2}$ shell.

Likelihood ratio tests are performed for the hypothesis that charged particle multiplicities measured in Au-Au and Cu-Cu collisions at $\sqrt{s_{NN}}=62.4$ and 200 GeV are distributed according to the negative binomial form. Results suggest that the hypothesis should be rejected in all classes of collision systems and centralities of Pioneering High-Energy Nuclear Interaction Experiment Relativistic Heavy Ion Collider measurements. However, the application of the least-squares test statistic with systematic errors included shows that for the collision system Au-Au at $\sqrt{s_{NN}}=62.4$ GeV the hypothesis could not be rejected in general.

We consider the effect of volume fluctuations on cumulants of the net baryon number. Based on a general formalism, we derive universal expressions for the net baryon number cumulants in the presence of volume fluctuations with an arbitrary probability distribution. The relevance of these fluctuations for the baryon-number cumulants and in particular for the ratios of cumulants is assessed in the Polyakov loop extended quark-meson model within the functional renormalization group. We show that the baryon number cumulants are generally enhanced by volume fluctuations and that the critical behavior of higher-order cumulants may be modified significantly.

We present new results for the phase space factors involved in double-$\beta$ decay for ${\beta }^{-}{\beta }^{-}$ transitions to ground states and excited $0_1^{+}$ states for isotopes of experimental interest. The Coulomb distortion of the electron wave functions is treated by solving numerically the Dirac equation with inclusion of the finite nuclear size and electron screening effects and using a Coulomb potential derived from a realistic proton density distribution in the daughter nucleus. Our results are compared with other results from literature, obtained in different approximations, and possible causes that can result in differences are discussed.

Nuclear polarization corrections to the $2P$-$2S$ Lamb shift in $\mu$-$d$ atoms are developed in order (${\alpha }^5$), and are shown to agree with a recent calculation. The nuclear physics in the resulting corrections is then evaluated in zero-range approximation. The dominant part of the correction is very simple in form and differs from a recent potential model calculation by less than 1%. It is also demonstrated how the third Zemach moment contribution largely cancels against part of the polarization correction, as it did in $e$-$d$ atoms and does so exactly for pointlike nucleons. This suggests that it may be possible to reduce the uncertainty in the theory (of which nuclear polarization is the largest contributor) to less than 1%.

We discuss the correlation of the spin-singlet two-neutron pair, the dineutron correlation, in the ground and excited $0^{+}$ states of ${}^8$He by using a method to describe the dineutron correlation in neutron-rich nuclei: the dineutron condensate wave function. The shell-model configuration and the dineutron configuration are mixed with each other in the ground state of ${}^8$He. We compare the ground state structure of ${}^8$He with that of ${}^6$He and suggest that the dineutron correlation is weaker in the ground state of ${}^8$He than in ${}^6$He. We also suggest the possibility of dineutron condensation in an excited $0^{+}$ state of ${}^8$He. In addition, we investigate the formation mechanism of the dineutron condensation in ${}^8$He by using a newly developed framework, the $\alpha$ and dineutron condensate wave function, and conclude that the attraction from the core is essential for the formation of the dineutron condensation.

The chiral doublet bands were claimed to be found in several silver isotopes. In the present study of negative parity bands of the odd-even ${}^{103,105,107}$Ag, by using the principal cranking Nilsson-Strutinsky approach it is demonstrated from the point view of spectroscopy that the nearly degenerate $\Delta I=1$ doublet bands could be built on the same configuration with different signature combination of one unpaired proton and two unpaired neutrons. Combining with the small triaxial deformation calculated ($\gamma <{15}^{\circ }$), the existence of chiral rotation in ${}^{103,105,107}$Ag is strongly questioned. In odd-odd ${}^{106}$Ag, the candidate chiral rotational band which possesses much larger moments of inertia than the yrast band, analogously to similar bands observed in ${}^{105,107}$Ag, is assigned to a configuration with two more neutrons in the $\nu 1h_{11/2}$ orbitals than its yrast partner. Such assignment will almost double the $B\left(E2\right)$ values within the band compared to the yrast band, which is consistent with the primary experimental observation.

Recoil distance Doppler-shift and Doppler-shift attenuation lifetime measurements were carried out for levels in ${}^{155}$Dy through the coincident detection of $\gamma$ rays. Twenty-six lifetimes, most of them for the first time, were determined using the differential decay curve method for the analysis of the data. At low and medium spins, particle-plus-triaxial-rotor calculations reveal different quadrupole deformations for the one-quasineutron bands in this transitional nucleus. At high spin, the reduced $B\left(E2\right)$ transition probabilities confirm with a better precision the results of a previous study implying decreased collectivity with increasing spin.

The thermodynamics of pairing phase-transition in nuclei is studied in the canonical ensemble and treating the pairing correlations in a finite-temperature variation after projection BCS approach (FT-VAP). Due to the restoration of particle number conservation, the pairing gap and the specific heat calculated in the FT-VAP approach vary smoothly with the temperature, indicating a gradual transition from the superfluid to the normal phase, as expected in finite systems. We have checked that the predictions of the FT-VAP approach are very accurate when compared to the results obtained by an exact diagonalization of the pairing Hamiltonian. The influence of pairing correlations on specific heat is analyzed for the isotopes ${}^{161,162}$Dy and ${}^{171,172}$Yb. It is shown that the FT-VAP approach, applied with a level density provided by mean field calculations and supplemented, at high energies, by the level density of the back-shifted Fermi gas model, can approximate reasonably well the main properties of specific heat extracted from experimental data. However, the detailed shape of the calculated specific heat is rather sensitive to the assumption made for the mean field.

In the paper, the results of analysis of elastic scattering and breakup processes in interactions of the ${}^{11}$Li nucleus with protons are presented. The hybrid model of the microscopic optical potential (OP) is applied. This OP includes the single-folding real part, while its imaginary part is derived within the high-energy approximation theory. For ${}^{11}\mathrm{Li}+p$ elastic scattering, the microscopic large-scale shell model (LSSM) density of ${}^{11}$Li is used. The depths of the real and imaginary parts of the OP are fitted to the elastic scattering data at 62, 68.4, and 75 MeV/nucleon, being simultaneously adjusted to reproduce the true energy dependence of the corresponding volume integrals. The role of the spin-orbit potential is studied and predictions for the total reaction cross sections are made. Also, the cluster model, in which ${}^{11}$Li consists of a $2n$-halo and the ${}^9$Li core having its own LSSM form of density, is adopted. The respective microscopic proton-cluster OPs are calculated and folded with the density probability of the relative motion of both clusters to get the whole ${}^{11}\mathrm{Li}+p$ OP. The breakup cross sections of ${}^{11}$Li at 62 MeV/nucleon and momentum distributions of the cluster fragments are calculated. An analysis of the single-particle density of ${}^{11}$Li within the same cluster model accounting for the possible geometric forms of the halo-cluster density distribution is performed.

The di-hadron angular correlation function is computed within boost-invariant, ideal hydrodynamics for $\mathrm{Au}+\mathrm{Au}$ collisions at ${\sqrt{s}}_{\mathit{NN}}=200$ GeV using Monte Carlo Glauber fluctuating initial conditions. When $0<p_T<3$ GeV, the intensity of the flow components and their phases, $\{v_n,{\Psi }_n\}$ ($n=2,3$), are found to be correlated on an event-by-event basis to the initial condition geometrical parameters $\{{\varepsilon }_{2,n},{\Phi }_{2,n}\}$, respectively. Moreover, the fluctuation of the relative phase between trigger and associated particles, ${\Delta }_n={\Psi }_n^t-{\Psi }_n^a$, is found to affect the di-hadron angular correlation function when different intervals of transverse momentum are used to define the trigger and the associated hadrons.

The nucleon resonances are investigated within a dynamical coupled-channels model of $\pi N$ and $\gamma N$ reactions up to the invariant mass $W=2$ GeV. The meson-baryon ($MB$) channels included in the calculations are $MB=$ $\pi N$, $\eta N$, $K\Lambda$, $K\Sigma$, and $\pi \pi N$ that has $\pi \Delta$, $\rho N$, and $\sigma N$ resonant components. The meson-baryon amplitudes $T_{M^{\prime }{B}^{\prime },MB}\left(W\right)$ are calculated from solving a set of coupled-channels integral equations defined by an interaction Hamiltonian consisting of (a) meson-exchange interactions $v_{M^{\prime }{B}^{\prime },MB}$ derived from phenomenological Lagrangian and (b) vertex interactions $N^{*}\to MB$ for describing the transition of a bare excited nucleon state $N^{*}$ to a meson-baryon channel $MB$.  The parameters of $v_{M^{\prime }{B}^{\prime },MB}$ are mainly constrained by the fit to the data of $\pi N\to \pi N$ in the low-energy region up to $W=1.4$ GeV. The bare masses of $N^{*}$ and the $N^{*}\to MB$ parameters are then determined in simultaneous fits to the data of $\pi N\to \pi N$ up to $W=2.3$ GeV and those of $\pi N\to \eta N,K\Lambda ,K\Sigma$ and $\gamma N\to \pi N,\eta N,K\Lambda ,K\Sigma$ up to $W=2.1$ GeV. The pole positions and residues of nucleon resonances are extracted by analytically continuing the meson-baryon amplitudes $T_{M^{\prime }{B}^{\prime },MB}\left(W\right)$ to the complex Riemann energy surface. From the extracted residues, we have determined the $N^{*}\to \pi N,\gamma N,\eta N,K\Lambda ,K\Sigma$ transition amplitudes at resonance poles. We compare the resonance pole positions from our analysis with those given by the Particle Data Group and the recent coupled-channels analyses by the Jülich and Bonn-Gatchina groups. Four results agree well only for the first $N^{*}$ in each spin-parity-isospin $(J^P,I)$ channel. For higher mass states, the number of states and their resonance positions from four results do not agree well. We discuss the possible sources of the discrepancies and the need of additional data from new hadron facilities such as the Japan Proton Accelerator Research Complex.

We introduce a fully antisymmetrized treatment of three-cluster dynamics within the ab initio framework of the no-core shell model/resonating-group method. Energy-independent nonlocal interactions among the three nuclear fragments are obtained from realistic nucleon-nucleon interactions and consistent ab initio many-body wave functions of the clusters. The three-cluster Schrödinger equation is solved with bound-state boundary conditions by means of the hyperspherical-harmonic method on a Lagrange mesh. We discuss the formalism in detail and give algebraic expressions for systems of two single nucleons plus a nucleus. Using a soft similarity-renormalization-group evolved chiral nucleon-nucleon potential, we apply the method to a ${}^4\mathrm{He}+n+n$ description of ${}^6\mathrm{He}$ and compare the results to experiment and to a six-body diagonalization of the Hamiltonian performed within the harmonic-oscillator expansions of the no-core shell model. Differences between the two calculations provide a measure of core (${}^4\mathrm{He}$) polarization effects.

In the present work we discuss the modifications of infinite nuclear matter properties. The modifications are performed in the framework of the in-medium modified Skyrme model. The model is developed to study the properties of in-medium nucleons and nucleonic systems. The mesonic sector of the model contains the nonlinear pion fields propagating in the nuclear medium. The properties of in-medium pions are defined by the pion-nucleus optical potential. The isospin-breaking part of the optical potential and the isospin-breaking effects in the mesonic sector generate the isospin-breaking effects in the baryonic sector. Further, the isospin-breaking effects in the baryonic sector are related to the asymmetric-matter properties. First, we discuss the binding energy per nucleon and the bulk properties of the isospin-symmetric nuclear matter. Then, we include the isospin-breaking effects and discuss the asymmetric-matter properties.

Background: The determination of the density dependence of the nuclear incompressibility can be investigated using the isoscalar giant monopole resonance.

Purpose: The importance of the so-called crossing density at subsaturation density is underlined.

Methods: The measurements of the isoscalar giant monopole resonance (GMR), also called the breathing mode, are analyzed with respect to their constraints on the quantity $M_c$, e.g., the density dependence of the nuclear incompressibility around the so-called crossing density ${\rho }_c=0.1$ fm${}^{-3}$.

Results: The correlation between the centroid of the GMR, $E_{\mathrm{GMR}}$, and $M_c$ is shown to be more accurate than the one between $E_{\mathrm{GMR}}$ and the incompressibility modulus at saturation density, $K_{\infty }$, giving rise to an improved determination on the nuclear equation of state. The relationship between $M_c$ and $K_{\infty }$ is given as a function of the skewness parameter $Q_{\infty }$ associated with the density dependence of the equation of state. The large variation of $Q_{\infty }$ among different energy density functionals directly impacts the knowledge of $K_{\infty }$: A better knowledge of $Q_{\infty }$ is required to deduce more accurately $K_{\infty }$. Using the local density approximation, a simple and accurate expression relating $E_{\mathrm{GMR}}$ and the quantity $M_c$ is derived and successfully compared to the fully microscopic predictions.

Conclusions: The measurement of the GMR constrains the slope of the incompressibility $M_c$ at the crossing density rather than the incompressibility modulus at the saturation density.

Elastic scattering observables (differential cross section and analyzing power) are calculated for the reaction ${}^6$He($p,p$)${}^6$He at projectile energies starting at 71 MeV/nucleon. The optical potential needed to describe the reaction is based on a microscopic Watson first-order folding potential, which explicitly takes into account that the two neutrons outside the ${}^4$He core occupy an open $p$ shell. The folding of the single-particle harmonic oscillator density matrix with the nucleon-nucleon $t$ matrix leads for this case to new terms not present in traditional folding optical potentials for closed shell nuclei. The effect of those new terms on the elastic scattering observables is investigated. Furthermore, we study the influence of an exponential tail of the $p$-shell wave functions on the scattering observables, as well as the sensitivity of the observables to variations of matter and charge radius. Finally, elastic scattering observables for the reaction ${}^8$He($p,p$)${}^8$He are presented at selected projectile energies.

Background: Quasifission, a fission-like reaction outcome in which no compound nucleus forms, is an important competitor to fusion in reactions leading to superheavy elements. The precise mechanisms driving the competition between quasifission and fusion are not well understood.

Purpose: To understand the influence reaction parameters have on quasifission probabilities, an investigation into the evolution of quasifission signatures as a function of entrance channel parameters is required.

Methods: Using the Australian National University's (ANU) CUBE detector for two-body fission studies, measurements were made for a wide range of reactions forming isotopes of curium. Important quasifission signatures—namely, mass-ratio spectra, mass-angle distributions, and angular anisotropies—were extracted.

Results: Evidence of quasifission was observed in all reactions, even for those using the lightest projectile (${}^{12}\text{C}+{}^{232}\text{Th}$). But the observables showing evidence of quasifission were not the same for all reactions. In all cases, mass distributions provided some evidence of the possible presence of quasifission but were not sufficient in most cases to clearly identify reactions for which quasifission was important. For reactions using light projectiles (${}^{12}$C, ${}^{28,30}$Si, ${}^{32}$S), experimental angular anisotropies provided the clearest signature of quasifission. For reactions using heavier projectiles (${}^{48}$Ti, ${}^{64}$Ni), the presence of mass-angle correlations in the mass-angle distributions provided strong evidence of quasifission and also provided information about quasifission timescales.

Conclusions: The observable offering the clearest signature of quasifission differs depending on the reaction timescale.

We study the medium modifications of baryon properties in nuclear many-body systems, especially in $\Lambda$ hypernuclei. The nucleon and the $\Lambda$ hyperon are described in the Friedberg-Lee model as nontopological solitons which interact through the self-consistent exchange of scalar and vector mesons. The quark degrees of freedom are explicitly considered in the model, so that the medium effects on baryons could be investigated. It is found that the model can provide reasonable descriptions for nuclear matter, finite nuclei, and $\Lambda$ hypernuclei. The present model predicts a significant increase of the baryon radius in nuclear medium.

Coincidence measurements of breakup fragments were carried out for the ${}^7\text{Li}+{}^{144}\text{Sm}$ and ${}^{6,7}\text{Li}+{}^{207,208}\text{Pb}$,${}^{209}\text{Bi}$ reactions at sub-barrier energies. Breakup modes in reactions of ${}^{6,7}\text{Li}$ were identified through the reaction $Q$ values, and the time-scales of each process inferred through the relative energy of the breakup fragments. Breakup was found to be predominantly triggered by nucleon transfer, with $p$ pickup leading to $\alpha +\alpha$ coincidences being the preferred breakup mode for ${}^7\text{Li}$, and $n$ stripping leading to $\alpha +p$ for ${}^6\text{Li}$. Breakup triggered by $2n$ stripping was also found to be prominent in the ${}^7\text{Li}+{}^{144}\text{Sm}$ reaction. The breakup yields were separated into prompt and delayed components based on the relative energies of the breakup fragments. This enables the identification of breakup process important in the suppression of complete fusion of ${}^{6,7}\text{Li}$ at above-barrier energies.