In-beam $\gamma$-ray spectroscopy was used to study excited states of the neutron-deficient nucleus ${}^{37}\mathrm{K}$ populated in fast-beam inelastic-scattering and proton-removal reactions at high-momentum loss. New $\gamma$-ray transitions and $\gamma \gamma$ coincidence relationships were established using the $\gamma$-ray tracking array GRETINA. The extension of the level scheme up to the first $(13/2^{-})$ state highlights the potential of this recently demonstrated population pathway for studies of isospin symmetry involving mirror-energy differences. The nature of the newly identified states is discussed in comparison to shell-model calculations with the FSU cross-shell effective interaction. The calculated occupation numbers of individual orbitals are shown to offer a consistent explanation of the measured mirror-energy differences between ${}^{37}\mathrm{K}$ and ${}^{37}\mathrm{Ar}$.

We report a new measurement of the half-life of ${}^{190}\mathrm{Ir}$, which was produced in a neutron stripping reaction using the electron beam from a linear accelerator at the National Centre for Nuclear Research (NCBJ). By observing the ${}^{190}\mathrm{Ir}$ decay for multiple half-life periods, we have determined a new value of $T_{1/2}=11.7511\pm 0.0020$ d, which represents the most precise determination of the ${}^{190}\mathrm{Ir}$ half-life to date. Our result improves upon the previously known value of 11.78(10) days by two orders of magnitude.

Background: The low-energy enhancement observed recently in the deexcitation $\gamma$-ray strength functions, suggested to arise due to the magnetic dipole $\left(M1\right)$ radiation, motivates theoretical efforts to improve the description of $M1$ strength in available nuclear structure models. Reliable theoretical predictions of nuclear dipole excitations are of interest for different nuclear applications and in particular for nuclear astrophysics, where the calculations of radiative capture cross sections often resort to theoretical $\gamma$ strength functions. The quasiparticle random-phase approximation (QRPA) approach is arguably the most widely spread microscopic tool in this context since it can be applied to heavy nuclei and at the scale of the entire chart.

Purpose: We aim to benchmark the performance of QRPA calculations with respect to $M1\gamma$ strength functions, with a special emphasis on the description of the low-energy effects observed in the deexcitation strength.

Methods: We investigate the zero-temperature and finite-temperature (FT) magnetic dipole strength functions computed within the QRPA and compare them to those obtained from exact diagonalizations of the same Hamiltonian in restricted orbital spaces. Our sample consists of 25 spherical and deformed nuclei, with masses ranging from $A=26$ to $A=136$, for which the exact diagonalization of the respective effective Hamiltonian in three different valence spaces remains feasible.

Results: We find a reasonable agreement for the total photoabsorption strengths between both many-body methods but show that the QRPA distributions are shown to be systematically shifted down in energy with respect to exact results. Photoemission strengths obtained within the FT-QRPA formalism appear insufficient to explain the low-energy enhancement of the $M1$ strength functions evidenced by the exact diagonalization approach.

Conclusions: We ascribe the problems encountered in the zero- and finite-temperature QRPA calculations to the lack of correlations in the nuclear ground state and to the truncation of the many-body space. In particular, the latter prevents obtaining the sufficiently high level density to produce the low-energy enhancement of the $M1$ strength function, making the (FT-)QRPA approach unsuitable for predictions of such effects across the nuclear chart.

A deep neural network (DNN) has been developed to generate the distributions of nuclear charge density, utilizing the training data from the relativistic density functional theory and incorporating available experimental charge radii of 1014 nuclei into the loss function. The DNN achieved a root-mean-square deviation of 0.0193 fm for charge radii on its validation set. Furthermore, the DNN can improve the description in both the tail and central regions of the charge density, enhancing agreement with experimental findings. The model's predictive capability has been further validated by its agreement with recent experimental data on charge radii. Finally, this refined model is employed to predict the charge density distributions in a wider range of nuclide chart, and the parameterized charge densities, charge radii, and higher-order moments of charge density distributions are given, providing a robust reference for future experimental investigations.

We present a benchmark study of the generator coordinate method (GCM) combined with eigenvector continuation (EC) in two different schemes for the low-lying states of the Lipkin-Meshkov-Glick (LMG) model, where the interaction strength is treated as a controlling parameter, simulating quantum many-body systems with the phase transition from noncollective to collective states. We demonstrate that the ${\mathrm{EC}}_{\mathrm{kmax}}$ scheme accurately reproduces the low-lying states of the LMG model. In this scheme, the EC basis consists of the wave functions of low-lying states up to the $k_{\max }$-th state of sampling Hamiltonians. Compared to ${\mathrm{EC}}_1$, which only includes the wave functions of the $k\mathrm{th}$ state of sampling Hamiltonians for the $k\mathrm{th}$ state of a target Hamiltonian, the ${\mathrm{EC}}_{\mathrm{kmax}}$ scheme exhibits significantly improved efficiency and accuracy. This study suggests the potential utilization of the extended EC scheme as an efficient emulator for GCM calculations.

The influence of the daughter nuclei deformations on the $\alpha$ decay's half-life is modeled by adding the term depending on the quadrupole deformation parameter value to the empirical relations for the $\alpha$-decay half-lives. It is shown that the addition of the deformation-dependent term led to a better description of the experimental data by the empirical expressions for the half-lives of the $\alpha$ decay than the ones without it. A new empirical expression for a description of the $\alpha$-decay half-lives is proposed. The empirical relation for the $\alpha$ decay half-lives for the transitions from the ground state to the ground state and the lowest $2^{+}$ state of the even-even nuclei is discussed.

We examine the $\mathrm{\Lambda }-{}^4\mathrm{He}$ ($\alpha$) momentum correlation in high-energy collisions to elucidate the interaction between Lambdas ($\mathrm{\Lambda }$) and nucleons ($N$). We compare phenomenological $\mathrm{\Lambda }\alpha$ potentials with different strengths at short range. In addition to the conventional Gaussian-type potentials, we construct the $\mathrm{\Lambda }\alpha$ potentials by substituting the nucleon density distribution in $\alpha$ particle into the Skyrme-type $\mathrm{\Lambda }$ potentials. We find that the dependence on the employed potential models is visible in the correlation functions from a small-size source. This indicates that the $\mathrm{\Lambda }\alpha$ momentum correlation could constrain the property of the $\mathrm{\Lambda }N$ interaction at high densities, which is expected to play an essential role in dense nuclear matter. Also, we verify that the Lednicky-Lyuboshits formula can yield erroneous results for a small-size source with a potential which has a large interaction range, like the $\mathrm{\Lambda }\alpha$ system.

The predictive power of the deformed relativistic Hartree-Bogoliubov theory in continuum (DRHBc) with density functional PC-PK1 is demonstrated for superheavy region ($101⩽Z⩽120$) by comparing with available experimental and evaluated data from AME2020. The DRHBc theory predicts 93 bound nuclei beyond the drip line $N=258$ in the region of $106⩽Z⩽112$, which form a stability peninsula. The odd-even differences between $\mathrm{odd}\text{−}N$ and even-$N$ nuclei are remarkable in the peninsula; the one-neutron separation energy of an $\mathrm{odd}\text{−}N$ nucleus is smaller than those of its neighboring even-$N$ nuclei due to the blocking effect, and as a result the number of bound $\mathrm{odd}\text{−}N$ nuclei is less than that of bound even-$N$ nuclei. The deformation effect is indispensable for the re-entrant stability beyond the drip line by significantly affecting the structure of single-particle levels around the Fermi energy. The interplay between deformation and pairing influences the location of the first bound $\mathrm{odd}\text{−}N$ nucleus in the peninsula. By examining the deformation effect at different orders, it is found that quadrupole deformation ${\beta }_2$ contributes predominantly to the appearance of stability peninsula, and the effects of higher-order deformations ${\beta }_4$ and ${\beta }_6$ are non-negligible.

Background: The commissioning of new sources of monochromatic $\gamma$ quanta will allow obtaining a large amount of new data on low-lying collective states of negative parity of even-even nuclei.

Purpose: To derive relations between observables characterizing low-energy negative parity states in even-even nuclei and to investigate the dependence of $E2$ transitions between low-energy collective states in these nuclei on the parity of states.

Methods: The Hamiltonian of the collective model and the fermionic $Q$-phonon representation of the vectors of collective states are used.

Results: Relations between different $E1$ transition matrix elements are derived and the parity dependence of $E2$ transitions is investigated.

Conclusion: Relations between the observables characterizing the low-lying collective states of both parities in even-even nuclei are obtained, which can be verified using experimental data produced by facilities generating intense monochromatic beams of $\gamma$ quanta.

We investigate parameter dependence of the calculated $\beta$-decay properties as well as low-lying states for the neutron-rich Zr isotopes within the neutron-proton interacting boson model (IBM-2) and interacting boson-fermion-fermion model (IBFFM-2). It is shown that the calculated ${log}_{10}ft$ values for the transitions of the $0_1^{+}$ ground states of the parent even-even nuclei ${}^{96–102}\mathrm{Zr}$ into the $1_1^{+}$ states of the daughter odd-odd nuclei ${}^{96–102}\mathrm{Nb}$ consistently exhibit a strong dependence on those parameters associated with the quadrupole-quadrupole boson interaction, and with the residual interaction between an unpaired neutron and an unpaired proton in the IBFFM-2 Hamiltonian for the odd-odd Nb nuclei. By the reduction in magnitude of the quadrupole-quadrupole interaction strength by approximately a factor of 2, the calculated ${log}_{10}ft$ values for the $\mathrm{Zr}\left(0_1^{+}\right)\to \mathrm{Nb}\left(1_1^{+}\right)$ transitions increase and agree with the experimental values. This points to a significant improvement over the previous study performed in the same mass region, that consists of the mapping from a relativistic energy density functional calculation onto the IBM-2 Hamiltonian.

The present work delves into compound nucleus formation probabilities in superheavy nuclei, developing empirical formulas incorporating deformation, entrance channel properties, and energy dependencies. The present formula also included shell correction. Experimental validation ensures the reliability of these formula. We have applied them to fusion reactions involved in synthesizing superheavy elements from $Z=104$ to 118, enhancing our understanding of nuclear structure and stability. Excitingly, the present study identifies fusion reactions with higher probabilities, potentially enabling the synthesis of elements with $Z=119$ and 120. The fusion reaction ${}^{58}\mathrm{Fe}+{}^{237}\mathrm{Np}$ and ${}^{64}\mathrm{Ni}+{}^{238}\mathrm{U}$ has a larger fusion probability among the attempted fusion reactions to synthesize superheavy elements $Z=119$ and 120, respectively. Such knowledge not only advances our understanding of nuclear dynamics but also informs future experiments aimed at synthesizing and characterizing elusive superheavy elements by bridging the gap between theory and experiment. The present work offers a roadmap for navigating this frontier, guiding experimental efforts toward achieving breakthroughs in superheavy element research.

With the time dependent Hartree-Fock (TDHF) theory, capture thresholds $E_{\mathrm{cap}}$ for 144 fusion systems with nearly spherical nuclei are systematically studied. We find that for the reactions between doubly magic nuclei, the calculated $E_{\mathrm{cap}}$ are very close to the extracted barrier heights from measured fusion excitation functions. For the fusion reactions with nearly spherical nuclei, an excitation energy of about 1 MeV at the capture position need to be considered to better reproduce the data due to the lower excitation threshold. The rms deviation with respect to the barrier heights is only 1.43 MeV from the TDHF calculations, which is smaller than the results from three empirical nuclear potentials. Together with Siwek-Wilczyński formula in which the three parameters are determined by the TDHF calculations, the measured fusion cross sections at energies around the barriers can be well reproduced for seven fusion reactions ${}^{40}\mathrm{Ca}+{}^{48}\mathrm{Ca}, {}^{16}\mathrm{O}+{}^{208}\mathrm{Pb}, {}^{40}\mathrm{Ca}+{}^{90,96}\mathrm{Zr}, {}^{28}\mathrm{Si}+{}^{96}\mathrm{Zr}$, and ${}^{132}\mathrm{Sn}+{}^{40,48}\mathrm{Ca}$.

The inclusive cross sections of one-proton removal from neutron-rich carbon isotopes ${}^{13–15}\mathrm{C}$ on a carbon target near $240\mathrm{MeV}/\mathrm{nucleon}$ were measured at the External Target Facility, HIRFL-CSR (Heavy Ion Research Facility in Lanzhou, Cooler Storage Ring). Together with the data for ${}^{12}\mathrm{C}$ and ${}^{16}\mathrm{C}$ at similar energies, the measurements are compared with Glauber model predictions weighted by spectroscopic strengths calculated by various shell models, namely standard shell model (SM), Gamow shell model (GSM), and no-core shell model (NCSM), which differ in the amount and aspects of included internucleon correlations. The dependencies of the spectroscopic strength reduction factor $R_{\mathrm{s}}$ on the binding depth $\mathrm{\Delta }S$ of the removed proton are plotted. The obtained $R_{\mathrm{s}}\text{−}\mathrm{\Delta }S$ relations of GSM and SM turn out to be largely consistent with the earlier-observed systematics, whereas the NSCM $R_{\mathrm{s}}$ exhibit an appreciable overall increase. GSM and NCSM predictions both compare better with experiment than SM and tend to alleviate the odd-even staggering of $R_{\mathrm{s}}$ against projectile mass number $A$. The $R_{\mathrm{s}}$ of ${}^{15}\mathrm{C}$ is intriguingly large compared with the rather low $R_{\mathrm{s}}$ of ${}^{16}\mathrm{C}$, for which the reason is discussed.

We estimate the spacetime profile of the electric field in head-on heavy-ion collisions at intermediate collision energies $\sqrt{s_{NN}}=\mathcal{O}(3–10\mathrm{GeV})$. Using a hadronic cascade model (JAM; Jet AA Microscopic transport model), we numerically demonstrate that the produced field has strength $eE=\mathcal{O}({(30–60\mathrm{MeV})}^2)$, which is supercritical to the Schwinger limit of QED and is non-negligibly large compared even to the hadron/QCD scale, and survives for a long time $\tau =\mathcal{O}(10\mathrm{fm}/c)$ due to the baryon stopping. We show that the produced field is nonperturbatively strong in the sense that the nonperturbativity parameters (e.g., the Keldysh parameter) are sufficiently large. This is in contrast to high-energy collisions $\sqrt{s_{NN}}\gtrsim 100\mathrm{GeV}$, where the field is extremely short-lived and hence is perturbative. Our results imply that the electromagnetic field may have phenomenological impacts on hadronic/QCD processes in intermediate-energy heavy-ion collisions and that heavy-ion collisions can be used as a new tool to explore strong-field physics in the nonperturbative regime.

We have studied the Seebeck and Nernst coefficients of a weakly magnetized hot QCD medium having a weak momentum anisotropy within the kinetic theory approach. The thermal medium effects have been incorporated in the framework of a quasiparticle model where the medium dependent mass of the quark has been calculated using perturbative thermal QCD in the presence of a weak magnetic field, which leads to different masses for the left ($L$) and right ($R$) handed chiral quark modes. We have found that the Seebeck and Nernst coefficient magnitudes for the individual quark flavors as well as for the composite medium are decreasing functions of temperature and decreasing functions of anisotropy strength. The Nernst coefficient magnitudes are about an order of magnitude smaller than their Seebeck counterparts, indicating the Seebeck effect constitutes a stronger response than the Nernst effect. The average percentage change corresponding to switching between quasiparticle modes ($L\to R$ or $R\to L$) is an order of magnitude smaller for Nernst coefficients, compared to the Seebeck coefficients.

A major complication in the search for jet quenching in proton- or deuteron-nucleus collision systems is the presence of physical effects which influence the experimental determination of collision centrality in the presence of a hard process. For example, in the proton color fluctuation picture, protons with a large Bjorken-$x$ ($x\gtrsim 0.1$) parton interact more weakly with the nucleons in the nucleus, leading to a smaller (larger) than expected yield in large (small) activity events. A recent measurement by the PHENIX Collaboration compared the yield of neutral pion and direct photon production in $d+\mathrm{Au}$ collisions, under the argument that the photon yields correct for such biases, and the difference between the two species is thus attributable to final-state effects (i.e., jet quenching). The main finding suggests a significant degree of jet quenching for hard processes in small systems. In this paper, I argue that the particular photon and pion events selected by PHENIX arise from proton configurations with significantly different Bjorken-$x$ distributions, and thus are subject to different magnitudes of modification in the color fluctuation model. Using the results of a previous global analysis of data from the BNL Relativistic Heavy Ion Collider (RHIC) and the CERN Large Hadron Collider (LHC), I show that potentially all of the pion-to-photon difference in PHENIX data can be described by a proton color fluctuation picture at a quantitative level before any additional physics from final-state effects is required. This finding reconciles the interpretation of the PHENIX measurement with others at RHIC and LHC, which have found no observable evidence for jet quenching in small systems.

Background: Angular momenta of fission fragments considerably higher than that of the fissioning nucleus have been observed in many experiments, raising the question of how these high angular momenta are generated. Wilson et al. have proposed a model for the angular momentum as a function of the mass of fission products based on the assumption that the angular momentum is generated from the collective motion of nucleons in the ruptured neck of the fissioning system. This assumption has caused a lot of debate in the community.

Purpose: To estimate the angular momenta of fission fragments based on the observed isomeric yield ratios in 25-MeV proton-induced fission of ${}^{238}\mathrm{U}$.

Method: A surrogate model of the fission code general description of fission observables (GEF) has been developed to generate properties of primary fission fragments. Based on the excitation energy and angular momentum of fission fragments from GEF, an energy-versus-angular-momentum matrix is reconstructed using a set of parameters. With such matrices as input, the reaction code TALYS is used to calculate the deexcitation of the fission fragments, including the population of the isomers, from which the isomeric yield ratios are obtained. By varying one of the parameters, the root-mean-square angular momentum ($J_{\mathrm{rms}}$), which determines the angular momentum distribution of the matrix, $J_{\mathrm{rms}}$-dependent isomeric yield ratios are obtained. Considering all primary fission fragments contributing to the isomeric yield ratio for a given fission product, the average angular momentum of those fragments is estimated.

Results: Data of 31 isomeric yield ratios in 25-MeV proton-induced fission of ${}^{238}\mathrm{U}$ were analyzed. From the analysis, the average $J_{\mathrm{rms}}$, equivalent to average angular momentum $J^{\mathrm{av}}$, with uncertainties are obtained for 24 fission products, while in seven cases no conclusive result for the angular momentum could be obtained. Furthermore, considering the neutron emissions of the primary fission fragments, the average angular momentum as a function of the average mass number of the primary fission fragment was estimated.

Conclusion: A mass dependency of the average angular momentum is observed in the proton-induced fission of ${}^{238}\mathrm{U}$. Moreover, the average angular momenta for mass numbers larger than 131 could be fairly well described by the parametrization proposed by Wilson et al. However, the average angular momenta of ${}^{130}\mathrm{Sn}$ and ${}^{131}\mathrm{Te}$ cannot be described by Wilson's model, which suggests a different lower limit for the validation of the parametrization in the model. In general, higher average angular momenta for $A\ge 132$ are observed in the present work compared to those from Wilson et al. This is likely due to the higher excitation energy of the fissioning nuclei in this work. Furthermore, the first systematic observation of the average angular momenta of fission products in the symmetric mass region is presented. In this region, a decreasing trend with mass number is observed, which cannot be explained by the proposal in Wilson's paper. Thus, a different mechanism is needed to explain this observation.