The mixed symmetry $2^{+}$ states in the $N=84$ isotones ${}^{142}\mathrm{Ce}$ and ${}^{144}\mathrm{Nd}$ are investigated within the quasiparticle-phonon model, with special attention to their $M1$ decay to the lowest symmetric $2^{+}$ state. The observed pronounced splitting of the $M1$ strength is shown to be caused by the phonon coupling, made quite effective by the peculiar shell structure of the two-valence neutrons above the $N=82$ shell closure.

In this first in a series of articles, we apply effective interactions derived by the unitary correlation operator method (UCOM) to the description of open-shell nuclei, using a self-consistent Hartree-Fock-Bogoliubov framework to account for pairing correlations. To disentangle the particle-hole and particle-particle channels and assess the pairing properties of $V_{\mathrm{UCOM}}$, we consider hybrid calculations using the phenomenological Gogny D1S interaction to derive the particle-hole mean field. In the main part of this article, we perform calculations of the tin isotopic chain using $V_{\mathrm{UCOM}}$ in both the particle-hole and particle-particle channels. We study the interplay of both channels and discuss the impact of noncentral and nonlocal terms in realistic interactions as well as the frequently used restriction of pairing interactions to the ${}^1{S}_0$ partial wave. The treatment of the center-of-mass motion and its effect on theoretical pairing gaps is assessed independently of the used interactions.

Continuum relativistic random-phase approximation (CRPA) is used to investigate collective excitation phenomena in several spherical nuclei along the periodic table. We start from relativistic mean-field calculations based on a covariant density functional with density-dependent zero-range forces. From the same functional an effective interaction is obtained as the second derivative with respect to the density. This interaction is used in relativistic CRPA calculations for the investigation of isoscalar monopole, isovector dipole, and isoscalar quadrupole resonances of spherical nuclei. In particular we study the low-lying $E1$ strength in the vicinity of the neutron evaporation threshold. The properties of the resonances, such as centroid energies and strengths distributions are compared with results of discrete RPA calculations for the same model as well as with experimental data.

Emission processes including $\alpha$ decay, heavy cluster decay, and proton and di-proton emission are analyzed in terms of the well-known factorization between the penetrability and the reduced width. By using a shifted harmonic oscillator plus Coulomb cluster-daughter interaction it is possible to derive a linear relation between the logarithm of the reduced width squared and the fragmentation potential, defined as the difference between the Coulomb barrier and the Q value. This relation is fulfilled with a good accuracy for transitions between ground states, as well as for most $\alpha$ decays to low-lying $2^{+}$ excited states. The well-known Viola-Seaborg rule, connecting half-lives with the Coulomb parameter and the product between fragment charge numbers, as well as the Blendowske scaling rule, connecting the spectroscopic factor with the mass number of the emitted cluster, can be easily understood in terms of the fragmentation potential. It is shown that the recently evidenced two regions in the dependence of reduced proton half-lives versus the Coulomb parameter are directly connected with the corresponding regions of the fragmentation potential.

Thermodynamics of clusterized matter is studied in the framework of statistical models with noninteracting cluster degrees of freedom. At variance with the analytical Fisher model, exact Metropolis simulation results indicate that the transition from homogeneous to clusterized matter lies along the $\rho ={\rho }_0$ axis at all temperatures and the limiting point of the phase diagram is not a critical point even if the surface energy vanishes at this point. Sensitivity of the inferred phase diagram to the employed statistical framework in the case of finite systems is discussed by considering the grand-canonical and constant-pressure canonical ensembles. A Wigner-Seitz formalism in which the fragment charge is neutralized by a uniform electron distribution allows one to build the phase diagram of neutron star matter as predicted by the cluster model.

We carry out an interacting shell-model study of binding energies and spectra in the $\mathit{sd}$-shell nuclei to examine the effect of truncation of the shell-model spaces. Starting with a Hamiltonian defined in a larger space and truncating to the $\mathit{sd}$ shell, the binding energies are strongly affected by the truncation, but the effect on the excitation energies is an order of magnitude smaller. We then refit the matrix elements of the two-particle interaction to compensate for the space truncation and find that it is easy to capture 90% of the binding energy shifts by refitting a few parameters. With the full parameter space of the two-particle Hamiltonian, we find that both the binding energies and the excitation energy can be fitted with remaining residual error about 5% of the average error from the truncation. Numerically, the rms initial error associated with our Hamiltonian is 3.4 MeV and the remaining residual error is 0.16 MeV. This is comparable to the empirical error found in $\mathit{sd}$-shell interacting shell-model fits to experimental data [B. A. Brown and W. A. Richter, Phys. Rev. C 74, 034315 (2006)].

We investigate the dineutron correlations in ${}^7\mathrm{H}$. The ground state of ${}^7\mathrm{H}$ is solved by superposing many AMD (antisymmetrized molecular dynamics) Slater determinants with various $t+n+n+n+n$ configurations based on AMD triple-S (AMD superposition of selected snapshots). The mixing of dineutron cluster components is estimated by calculating the squared overlap with the wave function of the dineutron condensate, which is an extension of the studies on the $\alpha$ condensate in $4N$ nuclei. The calculated results show significant mixing of components of dineutron clusters ($t+{}^{2}n+{}^{2}n$) with a spatially extended distribution ($~70\%$) much larger than that of ${}^8\mathrm{He}$, where the core nucleus is changed from $t$ to ${}^4\mathrm{He}$.

The Giessen Boltzmann-Uehling-Uhlenbeck transport model with relativistic mean fields is used to simulate $\overline{p}$-nucleus collisions. Antiproton absorption cross sections and momentum distributions of annihilation products are calculated by varying the $\overline{p}$ coupling strength to the mean meson fields. Parameters of the antiproton-nucleus optical potential are extracted from the comparison of the model calculations with experimental data.

Differential cross sections and hyperon polarizations have been measured for ${\overline{K}}^{0}n$, ${\pi }^0\Lambda$, and ${\pi }^0{\Sigma }^0$ production in $K^{-}p$ interactions at eight $K^{-}$ momenta between 514 and 750 MeV/$c$. The experiment detected the multiphoton final states with the Crystal Ball spectrometer using a $K^{-}$ beam from the BNL Alternating Gradient Synchrotron. The results provide significantly greater precision than the existing data, allowing a detailed reexamination of the excited hyperon states in our energy range.

We calculate formation spectra of the $\eta$-nucleus systems in the ($\pi ,N$) reactions with nuclear targets, which can be performed at existing and/or forthcoming facilities, including the Japan Proton Accelerator Research Complex, to investigate the $\eta$-nucleus interaction. Based on the $N^{*}(1535)$ dominance in the $\eta N$ system, the $\eta$-mesic nuclei are suitable systems for the study of in-medium properties of the $N^{*}(1535)$ baryon resonance, such as reduction of the mass difference of $N$ and $N^{*}$ in the nuclear medium, which affects the level structure of the $\eta$ and $N^{*}$-hole modes. We find that clear information on the in-medium $N^{*}$- and $\eta$-nucleus interactions can be obtained through the formation spectra of the $\eta$-mesic nuclei. We also discuss the experimental feasibilities by showing several spectra of the ($\pi ,N$) reactions calculated with possible experimental settings. Coincident measurements of the $N\pi$ pairs from the $N^{*}$ decays in nuclei help us to reduce backgrounds.

Transverse mass spectra for D mesons are calculated in $1+1$-dimensional hydrodynamics using different equations of state. Parameters of the simulations were tuned to describe proton spectra in heavy-ion collisions at RHIC. The assumption that the initial distribution of charm follows a scaling of binary collisions different from the bulk matter leads to significantly smaller effective slopes and mean $p_T$ value of the D-meson spectra, similar to the effect of a possible higher freeze-out temperature. This has to be taken into account in the interpretation of such spectra in the context of hydrodynamical models.

The triaxial rotor model with independent inertia and electric quadrupole tensors is applied to the $P_3$ term, $P_3=\langle 0_1\left|\right|\widehat{T}(E2)\left|\right|2_1\rangle \langle 2_1\left|\right|\widehat{T}(E2)\left|\right|2_2\rangle \langle 2_2\left|\right|\widehat{T}(E2)\left|\right|0_1\rangle$, which is a standard measure of quadrupole interference in collective nuclei. It is shown that the model naturally explains nuclei with anomalous signs for their $P_3$ terms. Measurements of $Q(2_1)$ in multiple-step Coulomb excitation can be significantly dependent on the sign of this term. The example of ${}^{194}\mathrm{Pt}$ is considered.

In this paper, the isospin dependent nucleon-nucleus optical potential theory is introduced on the basis of the effective Skyrme interactions. From the view of the many-body theory, the nucleon optical potential can be identified with the mass operator of the one-particle Green function. The first and second order mass operators of the one particle Green function in nuclear matter are derived, and the real and imaginary parts of the optical potential for finite nuclei are obtained as usual by applying a local density approximation. Our results, in most cases, can be derived and expressed analytically. From an extensive comparison with experimental data of various quantities of interests, it is concluded that for certain versions of Skyrme interactions without parameter adjusting the agreement between theory and experiments can be obtained satisfactorily. We define the ratio of the difference and summation of the neutron and proton nonelastic cross sections as the isospin effect value. The calculated results show that the isopin effect value decreases as the incident energy increases and increases as the asymmetric parameter ${\alpha }_0=(N\text{−}Z)/A$ of the target nucleus increases.

An analysis of inclusive quasielastic electron scattering is presented using different descriptions of the final-state interactions within the framework of the relativistic impulse approximation. The relativistic Green's function approach is compared with calculations based on the use of relativistic purely real mean-field potentials in the final state. Both approaches lead to a redistribution of the strength but conserving the total flux. Results for the differential cross section at different energies are presented. Scaling properties are also analyzed and discussed.

Within the generalized (non-Markovian) multidimensional Langevin approach, the time and energy characteristics of symmetric fission of highly excited heavy nuclei are studied. In two-dimensional space of the collective deformation parameters, it is considered a nuclear descent from the top of the fission barrier to the scission point. The distributions of descent times and total kinetic energy of fission fragments are calculated as functions of memory time, measuring the relative size of memory effects in the collective dynamics. We found that the peculiarities of the non-Markovian dynamics at fairly large values of the memory time are reflected in the saturation of the mean time of motion from the saddle to scission with the growth of the strength of memory effects in the system.

The $N^{*}(1535)$ resonance contributions to the $pn\to d\varphi$ reaction are evaluated in an effective Lagrangian model. The π-, $\eta$-, and ρ-meson exchange are considered. It is shown that the contributions from π- and ρ-meson exchange are dominant, while the contribution from $\eta$-meson exchange is negligibly small. Our theoretical results reproduce the experimental data of both total cross section and angular distribution well. This is more evidence that the $N^{*}(1535)$ resonance has a large $s\overline{s}$ component leading to a large coupling to $N\varphi$, which may be the real origin of the Okubo-Zweig-Iizuka rule violation in the $\pi N$ and $pN$ reactions.

Resonance-decay spectroscopy is used to study particle-unbound excited states produced in interactions of $E/A=10.7\hspace{0.5em}\mathrm{MeV}$ ${}^{10}\mathrm{C}$ on Be and C targets. After inelastic scattering, structures associated with excited states in ${}^{10}\mathrm{C}$ were observed at 5.22, 5.29, 6.55, 6.56, 6.57, and 8.4 MeV which decay into the $2p+2\alpha$ final state. This final state is created via a number of different decay paths, which include prompt and sequential two-proton decay to the ground state of ${}^8\mathrm{Be}$, $\alpha$ decay to ${}^6\mathrm{Be}{}_{\mathrm{g}.\mathrm{s}.}$, and proton decay to the 2.345-MeV state of ${}^9\mathrm{B}$. For the sequential two-proton decay states (5.22 and 6.55 MeV), angular correlations between the first two decay axes indicate that the spin of these states are nonzero. For the prompt two-proton decay of the 5.29-MeV state, the three-body correlations between the two protons and the core are intermediate between those measured for ground-state ${}^6\mathrm{Be}$ and ${}^{45}\mathrm{Fe}$ decays. The 6.55- and 6.57-MeV structures are most probably associated with the same level, which has a 14% two-proton decay branch with a strong “diproton” character and a 86% sequential two-proton decay branch. Correlations between the fragments following the three-body decay of the 2.345-MeV state of ${}^9\mathrm{B}$ can be approximately described by sequential $\alpha$ decay to the ${}^5\mathrm{Li}$ intermediate state. The 8.06- and 9.61-MeV ${}^{10}\mathrm{B}$ states that decay into the $d+{}^6\mathrm{Li}{}_{2.186}$ channel are confirmed. Evidence for cluster structure in ${}^{13}\mathrm{N}$ is obtained from a number of excited states that decay into the $p+3\alpha$ exit channel.

Two-nucleon separation energies are differences of binding energies. They provide important information on the relative stability of nuclei and, in particular, on shell gaps. In this work, the behavior of the decrements (change of slope) of two-nucleon separation energies has been studied. It has been shown that the bulk of this decrement at a shell-gap consists mainly of twice the difference of two effective single particle energies, plus a pairing correction. The decrement of the two-nucleon separation energies has a maximum (spike) for $N=Z$ nuclei. A comparison with values calculated by using a seniority binding energy formula shows that the spike is due to the Wigner energy. The evolution with nuclear mass of the isospin dependence of the Wigner energy is discussed.

We propose an application of the Kolmogorov-Smirnov test for rapidity distributions of individual events in ultrarelativistic heavy-ion collisions. The test is particularly suited to recognizing nonstatistical differences between the events. Thus when applied to a narrow centrality class it could indicate differences between events that would not be expected if all events evolved according to the same scenario. In particular, as an example we assume here a possible fragmentation of the fireball into smaller pieces at the quark/hadron phase transition. Quantitative studies are performed with a Monte Carlo model capable of simulating such a distribution of hadrons. We conclude that the Kolmogorov-Smirnov test is a very powerful tool for the identification of the fragmentation process.

We calculate the nuclear cross section for coherent and incoherent vector meson production within the QCD color dipole picture, including saturation effects. Theoretical estimates for scattering on both light and heavy nuclei are given over a wide range of energy.