Background: Because of its half-life of about 35 million years, ${}^{92}\text{Nb}$ is considered as a chronometer for nucleosynthesis events prior to the birth of our sun. The abundance of ${}^{92}\text{Nb}$ in the early solar system can be derived from meteoritic data. It has to be compared to theoretical estimates for the production of ${}^{92}\text{Nb}$ to determine the time between the last nucleosynthesis event before the formation of the early solar system.

Purpose: The influence of a low-lying short-lived isomer on the nucleosynthesis of ${}^{92}\text{Nb}$ is analyzed. The thermal coupling between the ground state and the isomer via so-called intermediate states affects the production and survival of ${}^{92}\text{Nb}$.

Method: The properties of the lowest intermediate state in ${}^{92}\text{Nb}$ are known from experiment. From the lifetime of the intermediate state and from its decay branchings, the transition rate from the ground state to the isomer and the effective half-life of ${}^{92}\text{Nb}$ are calculated as functions of the temperature.

Results: The coupling between the ground state and the isomer is strong. This leads to thermalization of ground state and isomer in the nucleosynthesis of ${}^{92}\text{Nb}$ in any explosive production scenario and almost 100% survival of ${}^{92}\text{Nb}$ in its ground state. However, the strong coupling leads to a temperature-dependent effective half-life of ${}^{92}\text{Nb}$ which makes the ${}^{92}\text{Nb}$ survival very sensitive to temperatures as low as about 8 keV, thus turning ${}^{92}\text{Nb}$ at least partly into a thermometer.

Conclusions: The low-lying isomer in ${}^{92}\text{Nb}$ does not affect the production of ${}^{92}\text{Nb}$ in explosive scenarios. In retrospect this validates all previous studies where the isomer was not taken into account. However, the dramatic reduction of the effective half-life at temperatures below 10 keV may affect the survival of ${}^{92}\text{Nb}$ after its synthesis in supernovae, which are the most likely astrophysical sites for the nucleosynthesis of ${}^{92}\text{Nb}$.

Knowledge of the nuclear level density is necessary for understanding various reactions, including those in the stellar environment. Usually the combinatorics of a Fermi gas plus pairing is used for finding the level density. Recently a practical algorithm avoiding diagonalization of huge matrices was developed for calculating the density of many-body nuclear energy levels with certain quantum numbers for a full shell-model Hamiltonian. The underlying physics is that of quantum chaos and intrinsic thermalization in a closed system of interacting particles. We briefly explain this algorithm and, when possible, demonstrate the agreement of the results with those derived from exact diagonalization. The resulting level density is much smoother than that coming from conventional mean-field combinatorics. We study the role of various components of residual interactions in the process of thermalization, stressing the influence of incoherent collision-like processes. The shell-model results for the traditionally used parameters are also compared with standard phenomenological approaches.

High-spin states in ${}^{134}\mathrm{Ce}$ have been investigated using the ${}^{116}\mathrm{Cd}({}^{22}\mathrm{Ne},4n)$ reaction and the Gammasphere array. The level scheme has been extended to an excitation energy of $\sim 30$ MeV and spin $\sim 54\hslash$. Two new dipole bands and four new sequences of quadrupole transitions were identified. Several new transitions have been added to a number of known bands. One of the strongly populated dipole bands was revised and placed differently in the level scheme, resolving a discrepancy between experiment and model calculations reported previously. Configurations are assigned to the observed bands based on cranked Nilsson-Strutinsky calculations. A coherent understanding of the various excitations, both at low and high spins, is thus obtained, supporting an interpretation in terms of coexistence of stable triaxial, highly deformed, and superdeformed shapes up to very high spins. Rotations around different axes of the triaxial nucleus, and sudden changes of the rotation axis in specific configurations, are identified, further elucidating the nature of high-spin collective excitations in the $A=130$ mass region.

The nuclear matrix elements (NMEs) corresponding to the neutrinoless double-$\beta$ ($0\nu \beta \beta$) decays to excited $0^{+}$ states of major experimental interest are calculated. All these decay transitions are electron emitting ($0\nu {\beta }^{-}{\beta }^{-}$ decays) and take place in the mass $A=76,82,96,100,110,116,124,130,136$ nuclei. This work is an extension of our previous work [Phys. Rev. C 91, 024613 (2015)], where $0\nu \beta \beta$ decays to the ground states of the same nuclei were treated. We calculate the NMEs for transitions mediated by both the light (l-NMEs) and the heavy (h-NMEs) Majorana neutrinos. A higher-QRPA (quasiparticle random-phase approximation) framework, the multiple-commutator model, is adopted for the calculations, including a previously omitted contribution to the transitions to two-phonon states. A Bonn $G$-matrix-based effective nucleon-nucleon interaction is generated by exploiting the recently proposed isoscalar-isovector decomposition of the particle-particle proton-neutron interaction parameter, $g_{\mathrm{pp}}$. All the appropriate short-range correlations, nucleon form factors, and higher-order nucleonic weak currents are included to benchmark our calculations. The relevant nuclear spectroscopy was checked to validate the nuclear models used. The computed l-NMEs and h-NMEs are compared with the available other calculations and the relevance of the new included two-phonon term is discussed. The results are summarized by easy-to-use half-life-Majorana-mass interrelations.

Fission fragment mass distributions in the reactions ${}^{11}\mathrm{B}+{}^{232}\mathrm{Th}$ and ${}^{11}\mathrm{B}+{}^{243}\mathrm{Am}$ were measured in an energy range around the barrier. No sudden change in the width of the mass distribution as a function of center-of-mass energy was observed at near-barrier energies, indicating no quasifission transition in the near-barrier energies. Interestingly, the previous measurements of fission fragment angular anisotropies for the same systems showed significant departure from the statistical saddle-point model predictions at near-barrier energies, indicating the presence of nonequilibrium fission processes.

Higher-order anisotropic flows in heavy-ion collisions are affected by nonlinear mode coupling effects. It has been suggested that the associated nonlinear hydrodynamic response coefficients probe the transport properties and are largely insensitive to the spectrum of initial density fluctuations of the medium created in these collisions. To test this suggestion, we explore nonlinear mode coupling effects in event-by-event viscous fluid dynamics, using two different models for the fluctuating initial density profiles, and compare the nonlinear coupling coefficients between the initial eccentricity vectors before hydrodynamic expansion and the final flow vectors after the expansion. For several mode coupling coefficients we find significant sensitivity to the initial fluctuation spectrum. They all exhibit strong sensitivity to the specific shear viscosity at freeze-out, but only weak dependence on the shear viscosity during hydrodynamic evolution.

Heavy-ion collisions at the Relativistic Heavy Ion Collider at Brookhaven National Laboratory and the Large Hadron Collider at CERN probe matter at extreme conditions of temperature and energy density. Most of the global properties of the collisions can be extracted from the measurements of charged-particle multiplicity and pseudorapidity ($\eta$) distributions. We have shown that the available experimental data on beam energy and centrality dependence of $\eta$ distributions in heavy-ion ($\mathrm{Au}+\mathrm{Au}$ or $\mathrm{Pb}+\mathrm{Pb}$) collisions from $\sqrt{s_{\mathit{NN}}}=7.7$ GeV to 2.76 TeV are reasonably well described by the AMPT model, which is used for further exploration. The nature of the $\eta$ distributions has been described by a double Gaussian function using a set of fit parameters, which exhibit a regular pattern as a function of beam energy. By extrapolating the parameters to a higher energy of $\sqrt{s_{\mathit{NN}}}=5.02$ TeV, we have obtained the charged-particle multiplicity densities, $\eta$ distributions, and energy densities for various centralities. Incidentally, these results match well with some of the recently published data by the ALICE Collaboration.

We introduce a generalized relaxation-time-approximation form of the collision term in the Boltzmann kinetic equation that allows for using different relaxation times for elastic and inelastic collisions. The efficacy of the proposed framework is demonstrated with the numerical calculations that describe systems with different relations between the two relaxation times and the evolution time of the system.

A recent paper by Id Betan and Nazarewicz reopened the problem of the absolute width of the $\alpha$ decay leading to a doubly magic nucleus. I point out a problematic aspect of this work, and reaffirm the correctness of the classical results.

We reply to the Comment by Lovas, which concerns the shell model calculations of the $\alpha$-decay width of ${}^{212}\mathrm{Po}$. In the Comment, the author claims that the $\alpha$-formation amplitudes obtained in our work “look unusual.” Here we reaffirm the results and conclusions of our original article.

In an experiment with the RIKEN projectile fragment separator called BigRIPS at the RIKEN Nishina Center, the fragmentation of a ${}^{78}\mathrm{Kr}$ beam allowed the observation of new neutron-deficient isotopes at the proton drip line. Clean identification spectra could be produced and ${}^{63}\mathrm{Se},{}^{67}\mathrm{Kr}$, and ${}^{68}\mathrm{Kr}$ were identified for the first time. In addition, ${}^{59}\mathrm{Ge}$ was also observed. Three of these isotopes, ${}^{59}\mathrm{Ge},{}^{63}\mathrm{Se}$, and ${}^{67}\mathrm{Kr}$, are potential candidates for ground-state two-proton radioactivity. In addition, the isotopes ${}^{58}\mathrm{Ge},{}^{62}\mathrm{Se}$, and ${}^{66}\mathrm{Kr}$ were also sought but without success. The present experiment also allowed the determination of production cross sections for some of the most exotic isotopes. These measurements confirm the trend already observed that the empirical parametrization of fragmentation cross sections, EPAX, significantly overestimates experimental cross sections in this mass region.

We study the interplay of quadrupole and octupole degrees of freedom in the structure of the isotope ${}^{144}\mathrm{Ba}$. A symmetry-conserving configuration-mixing method (SCCM) based on a Gogny energy density functional (EDF) has been used. The method includes particle number, parity, and angular momentum restoration as well as axial quadrupole and octupole shape mixing within the generator coordinate method. Predictions both for excitation energies and electromagnetic transition probabilities are in good agreement with the most recent experimental data.

The $\gamma$-ray strength functions and level densities of ${}^{73,74}\mathrm{Ge}$ have been extracted up to the neutron-separation energy $S_n$ from particle-$\gamma$ coincidence data using the Oslo method. Moreover, the $\gamma$-ray strength function of ${}^{74}\mathrm{Ge}$ above $S_n$ has been determined from photoneutron measurements; hence these two experiments cover the range of ${\mathrm{E}}_{\gamma }\approx 1$–13 MeV for ${}^{74}\mathrm{Ge}$. The obtained data show that both ${}^{73,74}\mathrm{Ge}$ display an increase in strength at low $\gamma$ energies. The experimental $\gamma$-ray strength functions are compared with $M1$ strength functions deduced from average $B\left(M1\right)$ values calculated within the shell model for a large number of transitions. The observed low-energy enhancements in ${}^{73,74}\mathrm{Ge}$ are adopted in the calculations of the ${}^{72,73}\mathrm{Ge}\left(n,\gamma \right)$ cross sections, where there are no direct experimental data. Calculated reaction rates for more neutron-rich germanium isotopes are shown to be strongly dependent on the presence of the low-energy enhancement.

The model dependence in the correlations of the neutron-skin thickness in heavy nuclei with various symmetry-energy parameters is analyzed by using several families of systematically varied microscopic mean-field models. Such correlations show a varying degree of model dependence once the results for all the different families are combined. Some mean-field models associated with similar values of the symmetry-energy slope parameter at saturation density $L$, and pertaining to different families, yield a greater-than-expected spread in the neutron-skin thickness of the ${}^{208}\mathrm{Pb}$ nucleus. The effective value of the symmetry-energy slope parameter $L_{\mathrm{eff}}$, determined by using the nucleon density profiles of the finite nucleus and the density derivative $S^{\prime }\left(\rho \right)$ of the symmetry energy starting from about saturation density up to low densities typical of the surface of nuclei, seems to account for the spread in the neutron-skin thickness for the models with similar $L$. The differences in the values of $L_{\mathrm{eff}}$ are mainly due to the small differences in the nucleon density distributions of heavy nuclei in the surface region and the behavior of the symmetry energy at subsaturation densities.

Excited states in ${}^{125}\mathrm{Cs}$ have been studied with the fusion-evaporation-reaction ${}^{116}\mathrm{Cd}({}^{14}\mathrm{N},5n)$ at 65-MeV beam energy. The level scheme of ${}^{125}\mathrm{Cs}$ was extended with the addition of more than 50 new γ transitions and with the identification of two new rotational bands built on the $\pi d_{5/2}$ and $\pi g_{7/2}$ configurations at low spins. The bandhead excitation energies of the previously known $\pi g_{9/2}$ and $\pi h_{11/2}$ bands were revised.

A detailed knowledge of the light ions interaction processes with matter is of great interest in basic and applied physics. As an example, particle therapy and space radioprotection require highly accurate fragmentation cross-section measurements to develop shielding materials and estimate acute and late health risks for manned missions in space and for treatment planning in particle therapy. The Fragmentation of Ions Relevant for Space and Therapy experiment at the Helmholtz Center for Heavy Ion research (GSI) was designed and built by an international collaboration from France, Germany, Italy, and Spain for studying the collisions of a ${}^{12}\mathrm{C}$ ion beam with thin targets. The collaboration's main purpose is to provide the double-differential cross-section measurement of carbon-ion fragmentation at energies that are relevant for both tumor therapy and space radiation protection applications. Fragmentation cross sections of light ions impinging on a wide range of thin targets are also essential to validate the nuclear models implemented in MC simulations that, in such an energy range, fail to reproduce the data with the required accuracy. This paper presents the single differential carbon-ion fragmentation cross sections on a thin gold target, measured as a function of the fragment angle and kinetic energy in the forward angular region ($\theta \lesssim 6^{\circ }$), aiming to provide useful data for the benchmarking of the simulation softwares used in light ions fragmentation applications. The ${}^{12}\mathrm{C}$ ions used in the measurement were accelerated at the energy of 400 MeV/nucleon by the SIS (heavy ion synchrotron) GSI facility.

Measurements of the anisotropic flow coefficients $v_2\left\{{\mathrm{\Psi }}_2\right\},v_3\left\{{\mathrm{\Psi }}_3\right\},v_4\left\{{\mathrm{\Psi }}_4\right\}$, and $v_4\left\{{\mathrm{\Psi }}_2\right\}$ for identified particles (${\pi }^{\pm },K^{\pm }$, and $p+\overline{p}$) at midrapidity, obtained relative to the event planes ${\mathrm{\Psi }}_m$ at forward rapidities in Au + Au collisions at $\sqrt{s_{{}_{NN}}}=200\mathrm{GeV}$, are presented as a function of collision centrality and particle transverse momenta $p_T$. The $v_n$ coefficients show characteristic patterns consistent with hydrodynamical expansion of the matter produced in the collisions. For each harmonic $n$, a modified valence quark-number $N_q$ scaling [plotting $v_n\left\{{\mathrm{\Psi }}_m\right\}/{\left(N_q\right)}^{n/2}$ versus transverse kinetic energies $\left({\mathrm{KE}}_T\right)/N_q]$ is observed to yield a single curve for all the measured particle species for a broad range of ${\mathrm{KE}}_T$. A simultaneous blast-wave model fit to the observed $v_n\left\{{\mathrm{\Psi }}_m\right\}\left(p_T\right)$ coefficients and published particle spectra identifies radial flow anisotropies ${\rho }_n\left\{{\mathrm{\Psi }}_m\right\}$ and spatial eccentricities $s_n\left\{{\mathrm{\Psi }}_m\right\}$ at freeze-out. These are generally smaller than the initial-state participant-plane geometric eccentricities ${\varepsilon }_n\left\{{\mathrm{\Psi }}_m^{\mathrm{PP}}\right\}$ as also observed in the final eccentricity from quantum interferometry measurements with respect to the event plane.