Finite amplitude method based on the deformed relativistic Hartree-Bogoliubov theory in continuum (DRHBc-FAM) is developed and applied to study isoscalar giant monopole resonance in exotic nuclei. Validation of the numerical implementation is examined for ${}^{208}\mathrm{Pb}$. The isoscalar giant monopole resonances for even-even calcium isotopes from ${}^{40}\mathrm{Ca}$ to the last bound neutron-rich nucleus ${}^{80}\mathrm{Ca}$ are calculated, and a good agreement with the available experimental centroid energies is obtained for ${}^{40\text{–}48}\mathrm{Ca}$. For the exotic calcium isotopes, e.g., ${}^{68}\mathrm{Ca}$ and ${}^{80}\mathrm{Ca}$, the DRHBc-FAM calculated results are closer to the energy weighted sum rule than the calculations on the harmonic oscillator basis, which highlights the advantages of DRHBc-FAM in describing giant resonances for exotic nuclei. In order to explore the soft monopole mode in the exotic nuclei, the giant monopole resonance for the deformed exotic nucleus ${}^{200}\mathrm{Nd}$ is investigated, where the prolate shape and the oblate shape coexist. A soft monopole mode near 6.0 MeV is found in the prolate case, and another one near 4.5 MeV is found in the oblate case. The transition density of the soft monopole mode shows in-phase or out-of-phase vibrations near the surface region, which is generated by quadrupole vibrations.

We studied the grand potential and phase transitions of an inhomogeneous finite volume spherical quark system. First the finite volume effects are considered by applying the multiple reflection expansion method which is an approximation for the density of states of the momentum in the grand potential of the finite size system. Then the density of states of momentum is further modified by the thermal fluctuations in the thermal system with the inhomogeneous field background. The modification of the density of states is calculated by the scattering phase shift from the Dirac equation of quarks in the inhomogeneous field background. By the numerical calculation we show how the phase transition is changed by varying the configuration of the inhomogeneous field background and find that the strong first order phase transition could be weakened or even changed to a crossover as a result.

The finite amplitude method (FAM) is a very efficient approach for solving the fully self-consistent random-phase approximation (RPA) equations. We use FAM to rederive the RPA matrices for Skyrme functionals, calculate the electric dipole $\left(E1\right)$ and the magnetic dipole $\left(M1\right)$ giant resonances, and compare the results with available experimental and evaluated data. For the $E1$ transitions in heavy nuclei, the calculations reproduce well the resonance energy of the photoabsorption cross sections. In the case of $M1$ transitions, we show that the residual interaction does not affect the transition strength of double-magic nuclei, which suggests that the spin terms in the Skyrme force currently neglected in the present computation could improve the agreement between FAM and experimental data.

The energy density functional (EDF) is applied to study $\alpha$ clustering and $\alpha$ scattering in light $A=4m$ nuclei. Our goal is to study the success of the EDF in predicting the ground-state $\alpha$ clustering in $4m$-conjugate nuclei. The $\alpha$-cluster density is obtained by optimizing the EDF with the help of the convolution theorem. The obtained cluster density reproduced the experimental binding energy of the considered nuclei. The obtained $\alpha$-cluster densities are investigated through the elastic scattering of $\alpha$ particles from ${}^{12}\mathrm{C}$, ${}^{16}\mathrm{O}$, ${}^{24}\mathrm{Ne}$, ${}^{24}\mathrm{Mg}$, ${}^{28}\mathrm{Si}$, ${}^{32}\mathrm{S}$, and ${}^{40}\mathrm{Ca}$ in the framework of the optical model. The real part of the optical model potential is calculated using $\alpha$-cluster single folding or the conventional double folding models based on the obtained densities. The obtained potentials are used to analyze the elastic scattering of $\alpha$-particle from (1) ${}^{12}\mathrm{C}$, ${}^{16}\mathrm{O}$, ${}^{24}\mathrm{Ne}$, ${}^{24}\mathrm{Mg}$, ${}^{28}\mathrm{Si}$, ${}^{32}\mathrm{S}$, and ${}^{40}\mathrm{Ca}$ at 104 MeV, (2) ${}^{12}\mathrm{C}$, ${}^{24}\mathrm{Mg}$, and ${}^{28}\mathrm{Si}$ at 120 MeV, (3) ${}^{12}\mathrm{C}$, ${}^{16}\mathrm{O}$, ${}^{24}\mathrm{Mg}$, ${}^{28}\mathrm{Si}$, and ${}^{40}\mathrm{Ca}$ at 130 MeV. The obtained results are very satisfactory and in agreement with experimental data. This success indicates the validity and applicability of the EDF in $\alpha$-cluster calculation for $A=4m$ nuclei.

Background: Unexplained variations of the decay rate parameter for weak interaction decays such as ${\beta }^{\pm }$ decay, electron capture, as well as strong interaction $\alpha$ decay have been reported. Because these variations have been presented by a number of groups, at various locations, using various types of detectors, different isotopes, and over extended periods of time, some researchers have interpreted the source of these variations as not from ambient environmental factors such as temperature, pressure, and humidity but via an unexplained fundamental interaction.

Purpose: The state of decay rate parameter variations experiments is reviewed, and the reported results are placed into a common comparable context by defining a phenomenological cross section. Then we make decay parameter measurements as a function of time at the level of ${10}^{-5}$ in the presences of an antineutrino flux with an on-off cycle time of $\approx$30 days. This level of precision requires a detailed understanding of both systematic and statistical errors; otherwise, systematic errors in the measurement may mimic the decay events of fundamental interactions.

Methods: The experiment searched for variation of the ${}_{25}{}^{54}\mathrm{Mn}$, $e^{-}$ capture decay rate parameter and ${}_{55}{}^{137}\mathrm{Cs}$, ${\beta }^{-}$ decay rate parameter both to a level of precision of 1 part in $\approx {10}^5$ by comparing the difference between the decay rate in the presence of an antineutrino flux $\approx 3\times {10}^{12}$ $\overline{\nu }$ ${\mathrm{cm}}^{-2}$ ${\mathrm{s}}^{-1}$ and no flux measurements. The experiment was located 6.53 m from the reactor core of the High Flux Isotope Reactor at the Oak Ridge National Laboratory. Two weak interaction decays, one via electron capture and the other via ${\beta }^{-}$ decay, were selected because the final state and the time reverse state each contain a neutrino and antineutrino, covering arguments that the antineutrino flux may interact differently or not at all in one of the cases.

Results: The $\gamma$ spectra from both decays were collected and analyzed independently. The measured variation in the decay rate parameters are found to be $\delta \lambda /\lambda =(0.034\pm 1.38)\times {10}^{-5}$ for ${}_{25}{}^{54}\mathrm{Mn}$ and $\delta \lambda /\lambda =(0.67\pm 1.56)\times {10}^{-5}$ for ${}_{55}{}^{137}\mathrm{Cs}$. These results are consistent with no measurable decay rate parameter variation due to an antineutrino flux, yielding a $68\%$ confidence level upper limit sensitivity for ${}_{25}{}^{54}\mathrm{Mn}$ $\delta \lambda /\lambda \le 1.31\times {10}^{-5}$ or $\sigma \le 1.29\times {10}^{-25}$ ${\mathrm{cm}}^2$ in cross section and for ${}_{55}{}^{137}\mathrm{Cs}$ $\delta \lambda /\lambda \le 2.23\times {10}^{-5}$ or $\sigma \le 5.69\times {10}^{-27}$ ${\mathrm{cm}}^2$.

Conclusions: The cross-section upper limit obtained in these null or no observable effect measurements are $\approx {10}^4$ times more sensitive than past experiments reporting positive results in ${}^{54}\mathrm{Mn}$ and ${}^{137}\mathrm{Cs}$.

Recent experiments have observed large anisotropic collective flows in high multiplicity proton-lead collisions at the CERN Large Hadron Collider (LHC), which indicates the possible formation of mini quark-gluon plasma (QGP) in small collision systems. However, no jet quenching has been confirmed in such small systems so far. To understand this intriguing result, the system size scan experiments have been proposed to bridge the gap between large and small systems. In this work, we perform a systematic study on both heavy and light flavor jet quenching in different collision systems at the LHC energies. Using our state-of-the-art jet quenching model, which combines the next-to-leading-order perturbative quantum chromodynamics framework, a linear Boltzmann transport model and the ($3+1$)-dimensional viscous hydrodynamics simulation, we provide a good description of nuclear modification factor $R_{\mathrm{AA}}$ for charged hadrons and $D$ mesons in central and midcentral $\mathrm{Pb}+\mathrm{Pb}$ and $\mathrm{Xe}+\mathrm{Xe}$ collisions measured by the CMS collaboration. We further predict the transverse momentum and centrality dependences of $R_{AA}$ for charged hadrons, $D$ and $B$ mesons in $\mathrm{Pb}+\mathrm{Pb}$, $\mathrm{Xe}+\mathrm{Xe}$, $\mathrm{Ar}+\mathrm{Ar}$, and $\mathrm{O}+\mathrm{O}$ collisions at the LHC energies. Our numerical results show a clear system size dependence for both light and heavy flavor hadron $R_{AA}$ across different collision systems. Sizable jet quenching effect is obtained for both heavy and light flavor hadrons in central $\mathrm{O}+\mathrm{O}$ collisions at the LHC energies. Our study provides a significant bridge for jet quenching from large to small systems, and should be helpful for finding the smallest QGP droplet and the disappearance of QGP in relativistic nuclear collisions.

We investigate the dineutron in the $2_1^{+}$ state of ${}^6\mathrm{He}$ via analysis of its decay mode by using the complex scaling method. In this Letter, we propose the cross section for the resonant state to distinguish the resonant contributions from the nonresonant ones. As a result, it is found that the shoulder peak appears in the cross section for the resonant state as a function of ${\varepsilon }_{n\text{−}n}$. Furthermore, we show that the $S=0$ component of the cross section, where $S$ is the total spin of the two valence neutrons, has a peak around the shoulder peak, which comes from the dineutron configuration in the $2_1^{+}$ state. Thus we conclude that the shoulder peak is expected to indicate the existence of the dineutron in the $2_1^{+}$ state.

Phenomenological amplitudes obtained in partial-wave analyses (PWA) of single-pion photoproduction are used to evaluate the contribution of this process to the Gerasimov-Drell-Hearn (GDH), Baldin, and Gell-Mann–Goldberger–Thirring (GGT) sum rules, by integrating up to $2\mathrm{GeV}$ in photon energy. Our study confirms that the single-pion contribution to all these sum rules converges even before the highest considered photon energy, but the levels of saturation are very different in the three cases. Single-pion production almost saturates the GDH sum rule for the proton, while a large fraction is missing in the neutron case. The Baldin integrals for the proton and the neutron are both saturated to about four fifths of the predicted total strength. For the GGT sum rule, the wide variability in predictions precludes any definitive statement.

Considering the effects of charge screening, we propose a new numerical recipe within the framework of the Thomas-Fermi approximation, where the properties of nuclear matter throughout a vast density range can be obtained self-consistently. Assuming spherical and cylindrical approximations for the Wigner-Seitz cell, typical nuclear matter structures (droplet, rod, slab, tube, bubble, and uniform) are observed. We then investigate the equations of state and microscopic structures of nuclear matter with both fixed proton fractions and $\beta$ equilibration, where two covariant density functionals, DD-LZ1 and DD-ME2, are adopted. Despite the smaller slope $L$ of symmetry energy obtained with the functional DD-LZ1, the curvature parameter $K_{\mathrm{sym}}$ is much larger than that of DD-ME2, which is attributed to the peculiar density-dependent behavior of meson-nucleon couplings guided by the restoration of pseudospin symmetry around the Fermi levels in finite nuclei. Consequently, different mass-radius relations of neutron stars are predicted by the two functionals. Different microscopic structures of nonuniform nuclear matter are obtained as well, which are expected to affect various physical processes in neutron star properties and evolutions.

With an extreme neutron-to-proton ratio of $N/Z=3, {}^8\mathrm{He}$ provides an ideal laboratory for the study of a variety of exotic phenomena, such as the emergence of a soft dipole mode that is dominated by transitions into the continuum. In this contribution, a covariant density-functional theory (DFT) framework is used to compute ground-state properties and the dipole response of ${}^8\mathrm{He}$. Although ${}^8\mathrm{He}$ is admittedly too light for DFT to be applicable, the great merit of the approach is that the spurious contamination associated with the center-of-mass motion is guaranteed to decouple from the physical response. Given that a strong mixing between the isoscalar and isovector dipole modes is expected for a system with such a large neutron-proton asymmetry as ${}^8\mathrm{He}$, the narrow structures that emerged at low energies in the isovector dipole response are attributed to the shift of the spurious strength to zero (or near zero) excitation energy. Thus, the theoretical framework implemented here disfavors the emergence of a soft dipole mode in ${}^8\mathrm{He}$.

We study fluctuations of particle number in the presence of a critical point by utilizing molecular dynamics simulations of the classical Lennard-Jones fluid in a periodic box. The numerical solution of the $N$-body problem naturally incorporates all correlations, exact conservation laws, and finite size effects, allowing us to study the fluctuation signatures of the critical point in a dynamical setup. We find that large fluctuations associated with the critical point are observed when measurements are performed in coordinate subspace, but, in the absence of collective flow and expansion, are essentially washed out when momentum cuts are imposed instead. We put our findings in the context of event-by-event fluctuations in heavy-ion collisions.

High-spin states of ${}^{90}\mathrm{Zr}$ have been investigated using the heavy-ion fusion-evaporation reaction ${}^{82}\mathrm{Se}({}^{13}\mathrm{C},5n)$ at a beam energy of 60 MeV. Excited levels of ${}^{90}\mathrm{Zr}$ have been observed up to an excitation energy of $\approx 13$ MeV and a spin of $\approx 20\hslash$ with the addition of thirty-two new $\gamma$-ray transitions to the proposed level scheme. Structures of both the positive- and negative-parity states up to the highest observed spin have been interpreted with shell-model calculations using the GWBXG interaction and a ${}^{68}\mathrm{Ni}$ core. Calculations suggest the role of neutron excitations across the $N=50$ shell gap for states with greater than 7 MeV excitation energy. High-spin states in these bands are interpreted to be generated by the recoupling of stretched proton and neutron configurations.

The radial overlap correction ${\delta }_{\mathrm{RO}}$ is reexamined for 30 superallowed $0^{+}\to 0^{+}$ nuclear $\beta$ decays using the shell model with Hartree-Fock (HF) radial wave functions. Our mean-field calculation is based on the effective Skyrme interaction including Coulomb, charge-symmetry-breaking (CSB), and charge-independence-breaking (CIB) terms. In addition, the electromagnetic corrections such as those due to the gradient of charge density, vacuum polarization, Coulomb spin orbit, and finite size of nucleons are also considered. In order to avoid the spurious isospin mixing, the local equivalent potential is constructed from the solution of a HF calculation for the $Z=N$ nucleus with charge-dependent forces neglected. Then the obtained mean field is solved noniteratively for the parent and daughter nuclei. It turns out that the CIB term has no significant impact on ${\delta }_{\mathrm{RO}}$ throughout the mass range between 10 and 74. On the other hand, the CSB term makes ${\delta }_{\mathrm{RO}}$ increase systematically between 10% and 30%. Similarly, the gradient density leads to a further increase of ${\delta }_{\mathrm{RO}}$ between 2% and 14%, while other estimated electromagnetic corrections are negligible. The effect of the suppression of isospin spuriosity is somewhat complicated. In general, it produces a significantly larger value of ${\delta }_{\mathrm{RO}}$; however, there are a few cases for which ${\delta }_{\mathrm{RO}}$ is mostly unaffected or even reduced, especially the even-even emitters in the light mass region. All these improvements partly explain the long-standing discrepancy between the correction values obtained with Woods-Saxon (WS) and HF radial wave functions. Nevertheless, the remaining discrepancy is still significant, except for the emitters with $A\le 26$. In addition, the local odd-even staggering present in the results obtained with the phenomenological potential [J. C. Hardy and I. S. Towner, Phys. Rev. C 102, 045501 (2020); L. Xayavong and N. A. Smirnova, Phys. Rev. C 97, 024324 (2018)] is not well reproduced by our calculations. This subsequently leads to a large difference in the predicted mirror $ft$ ratios. These problems might relate to the errors of the calculated charge radii as well as the deformation and other correlation effects on the data of separation energies used for constraining the asymptotic radial wave functions.

The region around the doubly magic nuclide ${}^{100}\mathrm{Sn}$ is very interesting for nuclear physics studies in terms of structure, reaction, and nuclear astrophysics. The main ingredients in nuclear structure studies using the shell model are the single-particle energies (spe) and the two-body matrix elements. To obtain the former, experimental data of ${}^{101}\mathrm{Sn}$ isotope spectrum are necessary. Since there are not enough experimental data, different approaches are used in the literature to obtain spe. In the sn100pn interaction, the hole excitation spectrum was used in ${}^{131}\mathrm{Sn}$ to determine neutron spe. The other approach is the use of the lightest isotope, ${}^{107}\mathrm{Sn}$, for which the model space orbitals are determined. In this study, we estimated the spectrum of the ${}^{101}\mathrm{Sn}$ isotope by an artificial neural network method in order to obtain neutron spe. After the training was carried out by using the experimental spectra of the nuclei around the ${}^{100}\mathrm{Sn}$ isotope, the ${}^{101}\mathrm{Sn}$ spectrum was obtained. Subsequently, neutron spe of the model space orbitals are defined. Shell-model calculations for ${}^{102–108}\mathrm{Sn}$ isotopes were carried out and results are compared to the experimental data and results obtained using the widely used interaction in the region, sn100pn. According to the results, it is seen that the Sn isotope spectra obtained with the new spe values are more compatible with the experimental data.

Nuclear reaction data for neutron induced reactions on unstable nuclei are critical for a wide range of applications spanning studies of nuclear astrophysics, nuclear reactor designs, and radiochemistry diagnostics. However, nuclear data evaluations of the reaction cross sections are largely based on calculations due to the difficulty in performing this class of measurements and the resulting lack of experimental data. For neutron induced charged particle reactions at fast neutron energies, at the MeV scale, these cross section predictions are predominately driven by statistical Hauser-Feshbach calculations. In this work, we present partial and total ${}^{59}\mathrm{Ni}(n,p)$ and ${}^{59}\mathrm{Ni}(n,\alpha )$ cross sections, measured directly with a radioactive ${}^{59}\mathrm{Ni}$ target, and compare the results to the present nuclear data evaluations. In addition, the results from this work are compared to a recent study of the ${}^{59}\mathrm{Ni}(n,xp)$ reaction cross section that was performed via an indirect surrogate ratio method. The expected energy trend of the cross section, based on the current work, is inconsistent with that of the surrogate work. This calls into question the reliability of that application of the surrogate ratio method and highlights the need for direct measurements on unstable nuclei, when feasible.

Bayesian analyses on both isoscalar and isovector nuclear interaction parameters are carried out based on the Korea-IBS-Daegu-SKKU (KIDS) model under the constraints of selected nuclear structure data of ${}^{208}\mathrm{Pb}$ and ${}^{120}\mathrm{Sn}$. Under the constraint of the neutron-skin thickness, it is found that incorporating the curvature parameter $K_{\mathrm{sym}}$ of the nuclear symmetry energy as an independent variable significantly broadens the posterior probability distribution function (PDF) of the slope parameter $L$ and affects the related correlations. Typically, the anticorrelation between $L$ and the symmetry energy at saturation density disappears, while a positive correlation between $L$ and $K_{\mathrm{sym}}$ is observed. Under the constraint of the isoscalar giant monopole resonance (ISGMR), incorporating the skewness parameter as an independent variable also significantly broadens the posterior PDF of the nuclear matter incompressibility $K_0$. Even with the broad uncertainties of higher-order parameters of the equation of state (EOS), robust constraints of $L<90\mathrm{MeV}$ and $K_0<270\mathrm{MeV}$ are obtained. Our results suggest some compatibility between the ISGMR data of ${}^{208}\mathrm{Pb}$ and ${}^{120}\mathrm{Sn}$ but not of the isovector observables, especially the neutron-skin thickness.

A simultaneous calculation for the shape evolution and the related spectroscopic properties of the low-lying states, and the $\beta$-decay properties in the even- and odd-mass Ge and As nuclei in the mass $A\approx 70–80$ region, within the framework of the nuclear density functional theory and the particle-core coupling scheme, is presented. The constrained self-consistent mean-field calculations using a universal energy density functional (EDF) and a pairing interaction determines the interacting-boson Hamiltonian for the even-even core nuclei, and the essential ingredients of the particle-boson interactions for the odd-nucleon systems, and of the Gamow-Teller and Fermi transition operators. A rapid structural evolution from $\gamma$-soft oblate to prolate shapes, as well as the spherical-oblate shape coexistence around the neutron subshell closure $N=40$, is suggested to occur in the even-even Ge nuclei. The predicted low-energy spectra, electromagnetic transition rates, and $\beta$-decay $logft$ values are in a reasonable agreement with experiment. The predicted $logft$ values reflect the structures of the wave functions for the initial and final nuclei of $\beta$ decay, which are, to a large extent, determined by the microscopic input provided by the underlying EDF calculation.

Background: Heavy-ion one-nucleon transfer reactions are promising tools to investigate single-particle configurations in nuclear states with and without the excitation of the core degrees of freedom. A careful determination of the spectroscopic amplitudes of these configurations is essential for the accurate study of other direct reactions as well as $\beta$ decays. In nucleon transfer reactions core excitations, for both target and projectile systems, are best approached via coupled-channels reaction schemes. Despite being notoriously demanding in terms of computing resources, coupled-channels analyses are progressively becoming more affordable even within model spaces large enough for tackling medium mass nuclei. In this context, the ${}^{76}\mathrm{Se}({}^{18}\mathrm{O},{}^{17}\mathrm{O}){}^{77}\mathrm{Se}$ reaction, here under study, gives a quantitative access to the relevant single-particle orbitals and core polarization configurations built on ${}^{76}\mathrm{Se}$. This is particularly relevant, since it provides data-driven information to constrain nuclear structure models for ${}^{76}\mathrm{Se}$, which is the daughter nucleus in the ${}^{76}\mathrm{Ge} \beta \beta$ decay. This reaction is one of the systems studied in the frame of the Nuclear Matrix Elements for Neutrinoless double beta decay project.

Purpose: We want to analyze transitions to low-lying excited states of the residual and ejectile nuclei in the ${}^{76}\mathrm{Se}({}^{18}\mathrm{O},{}^{17}\mathrm{O}){}^{77}\mathrm{Se}$ one-neutron stripping reaction at 275-MeV incident energy and determine the role of single-particle and core excitation in the description of the measured cross sections. In addition, we explore the sensitivity of the calculated cross section to different nuclear structure models.

Methods: The excitation energy spectrum and the differential cross-section angular distributions are measured using the MAGNEX large acceptance magnetic spectrometer for the detection of the ejectiles and the missing mass technique for the reconstruction of the reaction kinematics. The data are compared with calculations based on distorted-wave Born approximation, coupled-channels Born approximation, and coupled reaction channels adopting spectroscopic amplitudes for the projectile and target overlaps derived by large-scale shell-model calculations and interacting boson-fermion model.

Results: Peaks in the energy spectra corresponding to groups of unresolved transitions to ${}^{77}\mathrm{Se}$ and ${}^{17}\mathrm{O}$ are identified. The experimental cross sections are extracted and compared to theoretical calculations. A remarkable agreement is found, without using any scaling factors, demonstrating that the adopted models for nuclear structure and reaction take into account the relevant aspects of the studied processes. The main transitions which contribute to the cross section of each peak are identified.

Conclusions: The coupling with the inelastic channels feeding states in entrance and exit partitions is important in the one-neutron transfer reaction and should be accounted for in future analyses of other direct reactions such as single and double charge exchange processes involving ${}^{76}\mathrm{Se}$ isotope. The description of ${}^{77}\mathrm{Se}$ indicates the need of a large model space, in the view of an accurate description of the low-lying states, a feature that should be likely accounted even for $\beta \beta$-decay studies of ${}^{76}\mathrm{Ge}$.

The global spin alignment of vector mesons is a powerful probe to study the vorticity field of the system produced in noncentral relativistic heavy-ion collisions. However, the experimental correction of the global spin alignment observable remains a longstanding issue. In this study, we propose a method to correct for the effect of finite pseudorapidity coverage when extracting the azimuthal dependence of spin alignment parameter ${\rho }_{00}$. The potentially existing intrinsic spin alignment effects are taken into consideration together with the acceptance correction. The method presented in this paper is verified in a Monte Carlo simulation, it allows the measurements of azimuthal dependence of vector mesons global spin alignment to be conducted properly and accurately.