The evolution of quadrupole and octupole collectivity and their coupling is investigated in a series of even-even isotopes of the actinides Ra, Th, U, Pu, Cm, and Cf with neutron number in the interval $130⩽N⩽150$. The Hartree-Fock-Bogoliubov approximation, based on the parametrization D1M of the Gogny energy density functional, is employed to generate potential energy surfaces depending upon the axially symmetric quadrupole and octupole shape degrees of freedom. The mean-field energy surface is then mapped onto the expectation value of the $sdf$ interacting-boson-model Hamiltonian in the boson condensate state as to determine the strength parameters of the boson Hamiltonian. Spectroscopic properties related to the octupole degree of freedom are produced by diagonalizing the mapped Hamiltonian. Calculated low-energy negative-parity spectra, $B(E3;3_1^{-}\to 0_1^{+})$ reduced transition rates, and effective octupole deformation suggest that the transition from nearly spherical to stable octupole-deformed, and to octupole vibrational states occurs systematically in the actinide region.

The transverse wobbling motion in odd-$A$ nuclei is investigated by means of a semiclassical treatment applied to a triaxial rotor Hamiltonian with a rigidly aligned high-$j$ quasiparticle. An additional spin-spin interaction which accounts for the rotational alignment mechanism is used to generalize the quasiparticle-rotor coupling. Its effect on the rotation dynamics is investigated in a classical mainframe. The quantum realization of the excitations associated to the transverse wobbling regime in the presence of additional alignment is achieved in a harmonic approximation. The quality of the approximation is investigated in a general theoretical context and particularly when applied to transverse wobbling excitations observed in five $A\approx 160$ nuclei and suggested for ${}^{183}\mathrm{Au}, {}^{135}\mathrm{Pr}$, and ${}^{105}\mathrm{Pd}$.

In this paper, we calculate the cross sections for proton-induced reactions producing short-lived radionuclides like ${}^{7,10}\mathrm{Be}$, ${}^{26}\mathrm{Al}$, ${}^{53,54}\mathrm{Mn}$, etc., with the Liège intranuclear cascade model (incl$++$). The results show that the incl model, when coupled with the proper deexcitation model, gives satisfactory results for most of the considered reactions. Generally, results for reactions with $(\mathrm{\Delta }N-\mathrm{\Delta }Z)$ equal to 0 or 1 are more likely to precisely match experimental data than those for reactions with larger or smaller $|\mathrm{\Delta }N-\mathrm{\Delta }Z|$. Our results can provide useful references for both the users and developers of incl and deexcitation models.

The experimentally observed abnormal $\alpha$ flow behavior from heavy-ion collisions at intermediate energies is investigated using the events of ${}^{40}\mathrm{Ca}+{}^{40}\mathrm{Ca}$ at 35 MeV/nucleon simulated with an improved antisymmetrized molecular dynamics model with specific consideration of the Fermi motion in the nucleon-nucleon collision process. Its possible origins in the processes from the fragment formation to the experimental flow extraction, i.e., dynamical process, sequential decay, experimental detection, and data analysis, are closely examined. It is found that the observed abnormal $\alpha$ flow behavior originates from the reconstruction of reaction planes in the flow extraction. How the abnormal $\alpha$ flow behavior is generated from the reaction plane reconstruction procedure is discussed.

Recently, Chatterjee et al. [Phys. Rev. C 101, 034902 (2020)] used a hadronic transport model to estimate the resolution with which various experimental quantities select the impact parameter of relativistic heavy ion collisions at collision energies relevant to the Beam Energy Scan (BES) program at the Relativistic Heavy Ion Collider (RHIC). Measures based on particle multiplicity at forward rapidity were found to be significantly worse than those based on midrapidity multiplicity. Using the same model, we show that a slightly more sophisticated measure greatly improves the resolution based on forward rapidity particles; this improvement persists even when the model is filtered through a realistic simulation of a recent upgrade detector to the STAR experiment. These results highlight the importance of optimizing centrality measures based on particles detected at forward rapidity, especially for experimental studies that search for a critical point in the QCD phase diagram. Such measurements usually focus on proton multiplicity fluctuations at midrapidity, hence selecting events based on multiplicity at midrapidity raises the possibility of nontrivial autocorrelations.

We revisit the problem of particlization of a QCD fluid into hadrons and resonances at the end of the fluid dynamical stage in relativistic heavy-ion collisions in a context of fluctuation measurements. The existing methods sample an ideal hadron resonance gas, and therefore, they do not capture the non-Poissonian nature of the grand-canonical fluctuations, expected due to QCD dynamics such as the chiral transition or QCD critical point. We address the issue by partitioning the particlization hypersurface into locally grand-canonical fireballs populating the space-time rapidity axis that are constrained by global conservation laws. The procedure allows to quantify the effect of global conservation laws, volume fluctuations, thermal smearing, and resonance decays on fluctuation measurements in various rapidity acceptances and can be used in fluid dynamical simulations of heavy-ion collisions. As a first application, we study event-by-event fluctuations in heavy-ion collisions at the Large Hadron Collider (LHC) using an excluded volume hadron resonance gas model matched to lattice QCD susceptibilities, with a focus on (pseudo)rapidity acceptance dependence of net baryon, net proton, and net charge cumulants. We point out large differences between net proton and net baryon cumulant ratios that make direct comparisons between the two unjustified. We observe that the existing experimental data on net-charge fluctuations at the LHC shows a strong suppression relative to a hadronic description.

In this paper, we present the first beyond closure calculation for the neutrinoless double-$\beta$ decay of ${}^{76}\mathrm{Ge}$ to the first $2^{+}$ states of ${}^{76}\mathrm{Se}$ within the two nucleon mechanism. The isospin symmetry restored quasiparticle random-phase approximation method with the charge-dependent-Bonn realistic force is adopted for the nuclear structure calculations. We analyze the structure of the nuclear matrix elements and estimate the uncertainties from our nuclear many-body calculations. We find $g_{\mathrm{pp}}$ plays an important role for the calculations, and if quenching is included, suppression for the transition matrix element $M_{\lambda }$ is found. Our results for the transition matrix elements are about one order of magnitude larger than previous projected Hartree-Fock-Bogolyubov results with the closure approximation.

An experimental study of the isospin mixing in the mass region $A=60$ was made by measuring the $\gamma$ decay from the giant dipole resonance in the compound nuclei ${}^{60}\mathrm{Zn}$ and ${}^{62}\mathrm{Zn}$. These compound nuclei were populated at two different excitation energies, $E^{*}=47$ MeV and $E^{*}=58$ MeV using the fusion evaporation reactions ${}^{32}\mathrm{S}+{}^{28}\mathrm{Si}$ at the bombarding energy of 86 and 110 MeV and ${}^{32}\mathrm{S}+{}^{30}\mathrm{Si}$ at 75 and 98 MeV. In the experiment, performed at the Laboratori Nazionali di Legnaro of the Istituto Nazionale di Fisica Nucleare (INFN), the $\gamma$ rays were measured with the GALILEO detection system in which large-volume ${\mathrm{LaBr}}_3$(Ce) detectors were added to the HPGe detectors. The Coulomb spreading width was obtained from the comparison of the two reactions and then the isospin mixing parameter at zero temperature and the isospin-symmetry-breaking correction for beta decay were deduced. The present results were compared with data of the same type in other mass regions and with data from mass and beta-decay measurements and with theory. The present data allow us to deduce for the first time a consistent picture for mass dependence of isospin mixing and for the corresponding correction for the beta decay, supporting a reliable extension to the very interesting region of ${}^{100}\mathrm{Sn}$.

Quasiparticle-phonon coupling based on one quadrupole phonon is investigated to study the low-energy states of the $A\approx 130$ mass transitional region. The coupling is constructed by using the deformed average field of Nilsson, monopole pairing interaction, and quadrupole-quadrupole forces. Microscopic structure of the quadrupole phonon is given from the Tamm-Dancoff approximation. The effects of the recoil and Coriolis forces are included with the assumption of axially symmetric rotational motion. Since theoretical treatment is performed for odd-$A$ nuclei, the configuration of intrinsic states contains both one-quasiparticle and quasiparticle-phonon components. This model is applied to describe the systematic structure of ${}^{121}\mathrm{Cs}, {}^{125}\mathrm{Pr}$, and ${}^{123,125,127,129}\mathrm{La}$ nuclei, showing a reasonable agreement with the available experimental data at low excitation energies. From isotonic systematics, a strong Coriolis effect is revealed for negative-parity states and a strong pairing effect is shown for positive-parity ones. For the first time, the lowest (ground) $5/2^{+}$ state of ${}^{123,}\mathrm{La}$ is proposed to belong to the $1/2^{+}$[420] band from the isotopic systematic trend.

We study the in-medium effects in strangeness production in heavy-ion collisions at (sub)threshold energies of (1–2)$A$ GeV based on the microscopic Parton-Hadron-String Dynamics (PHSD) transport approach. The in-medium modifications of the antikaon $(\overline{K}=K^{-},{\overline{K}}^0)$ properties are described via the self-consistent coupled-channel unitarized scheme based on a SU(3) chiral Lagrangian which incorporates explicitly the $s$ and $p$ waves of the kaon-nucleon interaction. This scheme provides the antikaon potential, spectral functions, and reaction cross sections as well as their dependence on baryon density, temperature, and antikaon momentum in the nuclear medium, which are incorporated in the off-shell dynamics of the PHSD. The in-medium modification of kaons $(K=K^{+},K^0)$ are accounted via the kaon-nuclear potential, which is assumed to be proportional to the local baryon density. The manifestation of the medium effects in observables is investigated for the $K$ and $\overline{K}$ rapidity distributions, $p_T$ spectra, the polar and azimuthal angular distributions, and directed $\left(v_1\right)$ and elliptic $\left(v_2\right)$ flows in $\mathrm{C}+\mathrm{C}$, $\mathrm{Ni}+\mathrm{Ni}$, and $\mathrm{Au}+\mathrm{Au}$ collisions. We find—by comparison to experimental data from the KaoS, FOPI, and HADES Collaborations—that the modifications of (anti)kaon properties in nuclear matter are necessary to explain the data in a consistent manner. Moreover, we demonstrate the sensitivity of kaon observables to the equation of state of nuclear matter.

The CNO cycle is the main energy source in stars more massive than our Sun, it defines the energy production and the cycle time that lead to the lifetime of massive stars, and it is an important tool for the determination of the age of globular clusters. One of the largest uncertainties in the CNO chain of reactions comes from the uncertainty in the ${}^{14}\mathrm{N}(p,\gamma ){}^{15}\mathrm{O}$ reaction rate. This uncertainty arises predominantly from the uncertainty in the lifetime of the subthreshold state in ${}^{15}\mathrm{O}$ at $E_x=6792$ keV. Previous measurements of this state's lifetime are significantly discrepant. Here, we report on a new lifetime measurement of this state, as well as the excited states in ${}^{15}\mathrm{O}$ at $E_x=5181$ keV and $E_x=6172$ keV, populated via the ${}^{14}\mathrm{N}(p,\gamma ){}^{15}\mathrm{O}$ reaction at proton energies of $E_p=1020$ keV and $E_p=1570$ keV. The lifetimes have been determined with the Doppler-Shift Attenuation Method (DSAM) with three separate, nitrogen-implanted targets with Mo, Ta, and W backing. We obtained lifetimes from the weighted average of the three measurements, allowing us to account for systematic differences between the backing materials. For the 6792 keV state, we obtained a $\tau =0.6\pm 0.4$ fs. To provide cross-validation of our method, we measured the known lifetimes of the states at 5181 and 6172 keV to be $\tau =7.5\pm 3.0$ and $\tau =0.7\pm 0.5$ fs, respectively, in good agreement with previous measurements.

The nuclear symmetry energy is a key quantity in nuclear (astro)physics. It describes the isospin dependence of the nuclear equation of state, which is commonly assumed to be almost quadratic. In this work, we confront this standard quadratic expansion of the equation of state with explicit asymmetric nuclear-matter calculations based on a set of commonly used Hamiltonians including two- and three-nucleon forces derived from chiral effective-field theory. We study, in particular, the importance of nonquadratic contributions to the symmetry energy, including the nonanalytic logarithmic term introduced by Kaiser [Phys. Rev. C 91, 065201 (2015)]. Our results suggest that the nonquadratic contribution to the symmetry energy can be systematically determined from the various Hamiltonians employed, and we obtain $0.{74}_{-0.08}^{+0.11}$ MeV (or $-1.{02}_{-0.08}^{+0.11}$ MeV for the potential term with the effective-mass contribution) at nuclear saturation density, while the logarithmic contribution to the symmetry energy is relatively small and model-dependent. We also employ the meta-model approach to study the impact of the higher-order contributions on the neutron-star crust-core transition density, and find a 5% correction.

Two new excited bands built on the $\pi h_{11/2}$ configuration have been identified in ${}^{135}\mathrm{Nd}$ in addition to the known $\pi h_{11/2}$ band. The energy spectra of the excited bands and the available electromagnetic transition probabilities are in good agreement with theoretical results obtained using quasiparticle-plus-triaxial-rotor model calculations. The properties of the bands identify them as tilted precession bands instead of wobbling bands. Our results give a new insight into the interpretation of the low-lying bands in odd-$A$ mass nuclei, and can stimulate future studies to address the nuclear triaxiality.

The $5/2_1^{-}$, $9/2_1^{-}$, and $11/2_1^{-}$ states in ${}^{209}\mathrm{Po}$ were populated in the $\beta$ decay of ${}^{209}\mathrm{At}$ and their lifetimes measured using the electronic $\gamma \text{−}\gamma$ fast timing technique. The lifetime of the $9/2_1^{-}$ state is measured for first time. The lifetime of the $5/2_1^{-}$ is measured to be shorter than the value adopted in the literature while the lifetime of the $11/2_1^{-}$ state agrees well with the previous measurement. In order to get deeper insight into the structure of the states, a shell-model calculation was carried out adopting a microscopic effective interaction derived from the realistic CD-Bonn potential. The comparison between theoretical and experimental data for the low-lying negative-parity states of ${}^{209}\mathrm{Po}$ supports the reliability of the predicted wave functions, which are found to be dominated by the coupling of a neutron hole to the yrast states of ${}^{210}\mathrm{Po}$. However, it also points to the important role played by minor wave-function components in describing the reduced electromagnetic strengths, suggesting the need of additional configuration mixing for achieving a better quantitative agreement.

The finite amplitude method is implemented for covariant density functional theory with the point-coupling functional PC-PK1 for deformed nuclei. The giant monopole resonances for even-even nickel isotopes ${}^{58\text{–}68}\mathrm{Ni}$ are studied. The experimentally reported soft monopole mode, a distinct form of nuclear compressional mode, for the unstable nucleus ${}^{68}\mathrm{Ni}$ is well reproduced. The evolution of the soft monopole mode in neutron-rich nickel isotopes is shown. Microscopic analysis of the transition density shows that the soft monopole mode is dominated by neutron vibrations.

Background: Large argon-based neutrino detectors, such as those planned for the Deep Underground Neutrino Experiment, have the potential to provide unique sensitivity to low-energy (few to tens of MeV) electron neutrinos produced by core-collapse supernovae. Despite their importance for neutrino energy reconstruction, nuclear de-excitations following charged-current ${\nu }_e$ absorption on ${}^{40}\mathrm{Ar}$ have never been studied in detail at supernova energies.

Purpose: I develop a model of nuclear de-excitations that occur following the ${}^{40}\mathrm{Ar}({\nu }_e,e^{-}){}^{40}\mathrm{K}^{*}$ reaction. This model is applied to the calculation of exclusive cross sections.

Methods: A simple expression for the inclusive differential cross section is derived under the allowed approximation. Nuclear de-excitations are described using a combination of measured $\gamma$-ray decay schemes and the Hauser-Feshbach statistical model. All calculations are carried out using a novel Monte Carlo event generator called MARLEY (Model of Argon Reaction Low Energy Yields).

Results: Various total and differential cross sections are presented. Two de-excitation modes, one involving only $\gamma$ rays and the other including single neutron emission, are found to be dominant at few tens-of-MeV energies.

Conclusions: Nuclear de-excitations have a strong impact on the achievable energy resolution for supernova ${\nu }_e$ detection in liquid argon. Tagging events involving neutron emission, though difficult, could substantially improve energy reconstruction. Given a suitable calculation of the inclusive cross section, the MARLEY nuclear de-excitation model may readily be applied to other scattering processes.

Background: Johnson, Al-Khalili, and Tostevin constructed a theory for one-neutron halo-nucleus scattering, taking (1) the adiabatic approximation and (2) neglecting the interaction between a valence neutron and a target, and yielding a simple relationship between the elastic scattering of a halo nucleus and of its core. The core-target scattering is calculated with the reduced mass between a halo nucleus and a target, and hence is not measured with the experiment.

Purpose: Our first aim is to apply their theory for $\vec{p}+{}^6\mathrm{He}$ elastic scattering as two-neutron halo-nucleus scattering and improve the theory with (3) the eikonal approximation. Our second aim is to investigate how good the improved theory is.

Methods: An improved valence-target-cutting (VTC) theory and cluster-folding (CF) model.

Results: The improved VTC theory shows a new relation between two differential cross sections measured for $\vec{p}+{}^{4,6}\mathrm{He}$ scattering. Using the relation, we show that the analyzing power $A_y\left(q\right)$ for ${}^6\mathrm{He}$ is the same as for ${}^4\mathrm{He}$. In the improved theory, the ratio of measured differential cross section for ${}^4\mathrm{He}$ to that for ${}^6\mathrm{He}$ determines a radius $r_{\alpha -2n}$ between ${}^4\mathrm{He}$ and the center of mass of two valence neutrons; the value is $r_{\alpha -2n}=3.54$ fm. Among the approximations (1)–(3), the approximation (2) is essential. In order to investigate the approximation (2), we apply the CF model for $\vec{p}+{}^6\mathrm{He}$ scattering at 200 MeV, where the potential between $\vec{p}$ and ${}^4\mathrm{He}$ is fitted to data on $\vec{p}+{}^4\mathrm{He}$ scattering at 200 MeV. For $\vec{p}+{}^6\mathrm{He}$ scattering at 200 MeV, the CF model reproduces the measured differential cross section with no free parameter. The CF model shows that the approximation (2) is good in $0.9\lesssim q\lesssim 2.4{\mathrm{fm}}^{-1}$, where $\hslash q$ is the transfer momentum. Using the improved theory, in $0.9\lesssim q\lesssim 2.4{\mathrm{fm}}^{-1}$, we predict $A_y\left(q\right)$ for ${}^6\mathrm{He}$ from measured $A_y\left(q\right)$ for ${}^4\mathrm{He}$.

Conclusions: The improved VTC theory shows shows that $A_y\left(q\right)$ for ${}^6\mathrm{He}$ is the same as for ${}^4\mathrm{He}$.

In this work, we present a new prediction of the positron-proton to electron-proton elastic scattering cross sections ratio $R_{e^{+}{e}^{-}}$. While many phenomenological studies extracted the ratio $R_{e^{+}{e}^{-}}$ using proposed, model-independent parametrizations of the hard two-photon exchange (TPE) corrections to electron-proton ($\text{ep}$) elastic scattering cross section ${\sigma }_R$, we do not assume prior knowledge of the functional form of the hard TPE corrections to ${\sigma }_R$, and use combined unpolarized, and polarized $\text{ep}$ elastic scattering experimental data to extract the TPE contributions. We provide a simple parametrization of the TPE corrections to ${\sigma }_R$, along with the uncertainties associated with the model dependence of the extractions, and use our TPE parametrization to predict the ratio $R_{e^{+}{e}^{-}}$. We compare our prediction of $R_{e^{+}{e}^{-}}$ to several previous phenomenological extractions, TPE-hadronic calculations, and world's data with emphasis mainly on the kinematics range of the recent precise direct measurements from the CLAS, VEPP-3, and OLYMPUS experiments.

A $\beta$-decay unstable isomer with a half-life of 14.1 yr at 264 keV in ${}^{113}\mathrm{Cd}$ is a branching point in the $s$ process, from which a weak branch reaches to a rare tin isotope ${}^{115}\mathrm{Sn}$ whose astrophysical origin has been an open problem. We have measured $\gamma$ rays decaying to the ground state or the isomer in the ${}^{112}\mathrm{Cd}(n,\gamma ){}^{113}\mathrm{Cd}$ reaction using high-energy resolution detectors in conjunction with a time-of-flight method. The relative production ratios of the isomer to the total following the neutron capture reactions on ${}^{112}\mathrm{Cd}$ have been evaluated in an energy region of up to 9 keV, and the spin and parity of several resonances have been assigned.