Pion and $\eta$ electroproduction data are jointly analyzed for the first time, up to a center-of-mass energy of 1.6 GeV. The framework is a dynamical coupled-channels model, based on the recent Jülich-Bonn-Washington analysis of pion electroproduction data for the same energy range. Comparisons are made to a number of single-channel $\eta$ electroproduction fits. By comparing multipoles of comparable fit quality, we find some of these amplitudes are well determined over the near-threshold region, while others will require fits over an extended energy range.

In the $m$-scheme Hartree-Fock (HF) basis, we have developed an ab initio deformed single-reference in-medium similarity renormalization group (IMSRG) approach for open-shell nuclei. A deformed wave function may be more efficient in describing the deformed nucleus. The broken rotational symmetry can be restored using the angular momentum projection. However, a full angular momentum projection at the IMSRG level is still a challenge in both theory itself and computation. The angular momentum restoration mainly recaptures the static correlations, and in the present work we estimate the angular momentum projection effect by projecting the HF state as a leading-order approximation. As a test ground, we have calculated the deformed ${}^{8,10}\mathrm{Be}$ isotopes with the optimized chiral interaction ${\mathrm{NNLO}}_{\mathrm{opt}}$. The results are benchmarked with the no-core shell model and valence-space IMSRG calculations. Then we systematically investigate the ground-state energies and charge radii of even-even nuclei from light beryllium to medium-mass magnesium isotopes. The calculated energies are extrapolated to infinite basis space by an exponential form, and compared with extrapolated valence-space IMSRG results and experimental data.

We develop a class of emulators for solving quantum three-body scattering problems. They are based on combining the variational method for scattering observables and the recently proposed eigenvector continuation concept. The emulators are first trained by the exact scattering solutions of the governing Hamiltonian at a small number of points in its parameter space, and then employed to make interpolations and extrapolations in that space. Through a schematic nuclear-physics model with finite-range two and three-body interactions, we demonstrate the emulators to be extremely accurate and efficient. The computing time for emulation is on the scale of milliseconds (on a laptop), with relative errors ranging from ${10}^{-13}$ to ${10}^{-4}$ depending on the case. The emulators also require little memory. We argue that these emulators can be generalized to even more challenging scattering problems. Furthermore, this general strategy may be applicable for building the same type of emulators in other fields, wherever variational methods can be developed for evaluating physical models.

We present the quantum computation of nuclear observables where the operators of interest are first decomposed in terms of the linear combination of unitaries. Then we utilize the Hadamard test and the linear combination of unitaries based methods to compute the expectation values. We apply these methods to calculate the electric quadrupole moment of the deuteron. The results are compared for the Jordan-Wigner transformation and Gray code encoding. We discuss the versatility of our approach that can be utilized in general to calculate several observables on a quantum computer.

Data on hyperon form factors recently obtained from annihilation reactions are compared to each other and to proton and neutron form factors, in terms of two kinematical variables: the transferred momentum square, $q^2$, and the modulus $P$ of the relative momentum between the outgoing baryons. They are critically discussed in terms of possible correlated structures. The present status of the time-like form factor data for baryons is described and suggestions are given on the reactions and the kinematical range where data are desirable in order to clarify the arisen questions.

The diverse nature of the signal resulting from the phase transition of a neutron star to a quark star and the corresponding astrophysical observations are studied in the present work. The phase transition process is initiated by a density change at the star's center that deconfines matter, followed by weak combustion to attain absolutely stable strange quark matter. The weak combustion results in the generation of huge neutrino-antineutrino pairs, which annihilate and deposit energy on the star's surface. Structural changes due to the energy loss result in the star's misalignment angle evolution and generate gravitational waves. The energy budget and time signature for the neutrino-antineutrino annihilation are compared with the observed isotropic energy for a short $\gamma$-ray burst. The misalignment angle evolves to align with the star's symmetry axis, which leads to the sudden increase or decrease of radio intensity from the pulsar. The corresponding gravitational wave emission, both continuous and burst, also has a unique signature pointing towards astrophysical phase transition.

We use the Lipkin-Meshkov-Glick (LMG) model and the valence-space nuclear shell model to examine the likely performance of variational quantum eigensolvers in nuclear-structure theory. The LMG model exhibits both a phase transition and spontaneous symmetry breaking at the mean-field level in one of the phases, features that characterize collective dynamics in medium-mass and heavy nuclei. We show that with appropriate modifications, the ADAPT-VQE algorithm, a particularly flexible and accurate variational approach, is not troubled by these complications. We treat up to 12 particles and show that the number of quantum operations needed to approach the ground-state energy scales linearly with the number of qubits. We find similar scaling when the algorithm is applied to the nuclear shell model with realistic interactions in the $sd$ and $pf$ shells. Although most of these simulations contain no noise, we use a noise model from real IBM hardware to show that for the LMG model with four particles, weak noise has no effect on the efficiency of the algorithm.

We investigate deuteron-triton (DT) fusion in the presence of linearly polarized strong electromagnetic fields in the high-frequency limit, in which a complex spherical square-well potential is exploited to describe the nuclear potential. Within the framework of the Kramers-Henneberger (KH) transformation, we have calculated the total and angular differential fusion cross sections by investigating the asymptotical phase shifts of the Coulomb wave functions. Introducing a dimensionless quantity $n_{\mathrm{d}}$ representing the ratio of the particle quiver oscillation amplitude to the radius of nuclear potential, we find that, even though the tunneling probability of passing through the Coulomb repulsive potential remains almost identical to that in the absence of electromagnetic fields, the peaks of total cross sections and corresponding astrophysical $S$ factors show apparent shifts. For ins- tance, the peak of the astrophysical $S$ factor shifts from the well known value of 110 keV to 50 keV for $n_{\mathrm{d}}=0.15$. The angular differential cross sections also show some resonance peaks that shift from zero inclination angle to $\pi /2$ with increasing the parameter $n_{\mathrm{d}}$. With the help of Wentzel-Kramers-Brillouin (WKB) approximate wave functions, the shape-resonance tunneling mechanism of the above findings is uncovered and some implications are discussed.

We present high-precision measurements of elliptic, triangular, and quadrangular flow $v_2$, $v_3$, and $v_4$, respectively, at midrapidity for identified hadrons $\pi$, $p$, $K$, $\phi$, $K_s$, $\mathrm{\Lambda }$ as a function of centrality and transverse momentum in Au+Au collisions at the center-of-mass energy $\sqrt{s_{NN}}=200$ GeV. We observe similar $v_n$ trends between light and strange mesons which indicates that the heavier strange quarks flow as strongly as the lighter up and down quarks. The number-of-constituent-quark scaling for $v_2$, $v_3$, and $v_4$ is found to hold within statistical uncertainty for $0\text{–}10\%$, $10\text{–}40\%$, and $40\text{–}80\%$ collision centrality intervals. The results are compared to several viscous hydrodynamic calculations with varying initial conditions, and could serve as an additional constraint to the development of hydrodynamic models.

We present new calculations of the astrophysical $S$ factor and reaction rate for the ${}^6\mathrm{Li}(p,\gamma ){}^7\mathrm{Be}$ reaction at energies of 10 keV to 5 MeV in the framework of a modified potential cluster model with forbidden states, including low lying resonances. The astrophysical $S\left(E\right)$ factor is compared with the available experimental data and calculations done within different models. The results for the $S$ factor are in good agreement with the data set (for $E<0.3$ MeV) and calculations (for $E<0.6$ MeV) of the LUNA Collaboration [Phys. Rev. C 102, 052802(R) (2020)]. The recommended extrapolated zero value $S\left(0\right)$ turned out to be 101 eV b. Using the theoretical total cross sections, the ${}^6\mathrm{Li}(p,\gamma ){}^7\mathrm{Be}$ capture reaction rate is calculated at temperatures ranging from $0.01T_9$ to $10T_9$ and compared with NACRE and NACRE II. Analytical expressions for the $S$ factor and reaction rate are given, and the effect of low-lying resonances on the reaction rate is estimated. We suggest updating the NACRE and NACRE II databases in light of the new LUNA data and present calculations.

The SU(3) symmetry, the subgroup in the dynamic chain of the SU(6) group in the interacting boson model (IBM), corresponds to the Bohr-Mottelson rotor model for axially symmetric deformed nuclei. It is synonymous but not identical to it. The common characteristics of the two models and their contrasting features are illustrated. The effect of adding the pairing term in the IBM SU(3) Hamiltonian to bring it closer to the rotor model is highlighted. The modified SU(3) Hamiltonian expression breaks the degeneracy of the β and γ bands in the SU(3) spectrum. The different ways to produce the forbidden $E2$ transitions across the different (λ, μ)-multiplets are discussed. The related features of SL(3, R) symmetry group are illustrated. We point out that the additional pairing term affects only certain states, preserving the rotational features of the other states in the SU(3) spectrum.

The ${}^{44}\mathrm{Ti}$ nucleus is believed to have a ${}^{40}\mathrm{Ca}+\alpha$ cluster structure; however, $\alpha$ (${}^4\mathrm{He}$) cluster structure tends to be washed out when we allow its breaking due to the spin-orbit interaction. Nevertheless, $\alpha$ clustering in medium-heavy nuclei is a popular subject recently. The tensor interaction plays an essential role in the strong binding of the ${}^4\mathrm{He}$, which induces the two-particle–two-hole (2p2h) excitation. Since this tensor effect is blocked when another nucleus approaches, it becomes the salvation of the ${}^{40}\mathrm{Ca}+\alpha$ clustering in ${}^{44}\mathrm{Ti}$. The competition of spin-orbit and tensor effects is investigated in the medium-heavy region for the first time.

Nuclear matrix elements (NMEs) for two-neutrino double-$\beta$ decay ($2\nu \beta \beta$) are studied in the framework of a relativistic nuclear energy density functional. The properties of nuclei involved in the decay are obtained using the relativistic Hartree-Bardeen-Cooper-Schrieffer theory and relevant nuclear transitions are described using the relativistic proton-neutron quasiparticle random phase approximation based on the relativistic energy density functional. Three effective interactions are employed, including density-dependent meson-exchange (DD-ME2) and point-coupling interactions (DD-PC1 and DD-PCX), and pairing correlations are described consistently both in $T=1$ and $T=0$ channels using a separable pairing interaction. The optimal values of $T=0$ pairing strength parameter $V_{0pp}$ are constrained by the experimental data on $\beta$-decay half-lives. The $2\nu \beta \beta$ matrix elements and half-lives are calculated for several nuclides experimentally known to undergo this kind of decay:${}^{48}\mathrm{Ca}, {}^{76}\mathrm{Ge}, {}^{82}\mathrm{Se}, {}^{96}\mathrm{Zr}, {}^{100}\mathrm{Mo}, {}^{116}\mathrm{Cd}, {}^{124}\mathrm{Xe}, {}^{128}\mathrm{Te}, {}^{130}\mathrm{Te}, {}^{136}\mathrm{Xe}$, and ${}^{150}\mathrm{Nd}$. The model dependence of the NMEs and their sensitivity on $V_{0pp}$ is investigated, and the NMEs obtained using optimal values of $V_{0pp}$ are discussed in comparison to previous studies. The results of the present work represent an important benchmark for the future applications of the relativistic framework in studies of neutrinoless double-$\beta$ decay.

We study the effects of correlations beyond the independent particle model in the evaluation of neutron skins of various neutron-rich doubly magic nuclei. We consider short- and long-range correlations to take into account the presence of the strongly repulsive core of the bare nucleon-nucleon interaction and collective nuclear phenomena, respectively. Despite the strong sensitivity on the structure of the nucleus considered, our results indicate that, in general, correlations increase the values of the neutron skins.

We calculate the transverse momentum broadening $\widehat{q}$ and collisional energy loss $dE/dx$ of hard probes traversing an evolving glasma during the earliest phase of a relativistic heavy-ion collision. We use a Fokker-Planck equation and apply a proper time expansion to describe the temporal evolution of the glasma. The correlators of the chromodynamic fields that determine the Fokker-Planck collision terms, which in turn provide $\widehat{q}$ and $dE/dx$, are computed to fifth order. Both transport coefficients are strongly dependent on time. The maximum values they acquire before the proper time expansion breaks down are large: $\widehat{q}$ is of the order of a few ${\mathrm{GeV}}^2/\mathrm{fm}$ and $dE/dx\sim 1\mathrm{GeV}/\mathrm{fm}$. Their precise values depend on the probe's velocity $\mathbf{v}$, the saturation momentum $Q_s$, and an IR regulator $m$ that is related to the confinement scale. We study the dependence of our results on these quantities. Different regularization procedures are analyzed and shown to produce similar results. We also discuss the validity of the proper time expansion and the compatibility of the approximations that are inherent in the derivation of the Fokker-Planck equation. We show that hard probes lose a comparable amount of energy when they propagate through the short-lived glasma phase, and the long-lasting hydrodynamic phase. The conclusion is that the glasma plays an important role in jet quenching.

Nuclear magnetic-dipole ($M1$) and Gamow-Teller (GT) transitions provide insight into the spin-isospin properties of atomic nuclei. By considering them as unified spin-isospin transitions, the $M1$/GT transition strengths and excitation energies are subject to isospin symmetry. The excitation properties associated to the $M1$/GT symmetry need to be clarified within a consistent theoretical approach. In this work, the relationship between the $M1$ and GT transitions in Ca isotopes is investigated in a unified framework based on the relativistic energy-density functional (REDF) with point-coupling interactions, using the relativistic quasiparticle random-phase approximation (RQRPA). It is shown that the isovector-pseudovector (IV-PV) residual interaction affects both transitions, and the symmetry of $M1$ and giant-GT transitions is disrupted by this interaction in closed-shell nuclei. In open-shell Ca isotopes, the proton-neutron pairing in the residual RQRPA interaction also plays a role in GT transitions. Due to the interplay between these interactions, the $M1$/GT symmetry can be restored especially in the ${}^{42}\mathrm{Ca}$ nucleus, i.e., the giant-GT strength can become comparable to that of the $M1$ mode in terms of the unified spin-isospin transitions by adjusting the proton-neutron pairing strength to reproduce the experimental low-lying GT-excitation energies. The mirror symmetry of both $M1$ and GT transitions is also demonstrated for open-shell mirror partners, ${}^{42}\mathrm{Ca}$ and ${}^{42}\mathrm{Ti}$. Further improvements are required to achieve simultaneous reproduction of $M1$ and GT transition energies in the REDF framework.

Spectroscopic properties that characterize the shape phase transitions in krypton isotopes with the mass $A\approx 80$ region are investigated within the framework of the nuclear density functional theory. Triaxial quadrupole constrained self-consistent mean-field calculations that employ relativistic energy density functionals and a pairing interaction are carried out for the even-even nuclei ${}^{76-86}\mathrm{Kr}$. The spectroscopic properties are computed by solving the triaxial quadrupole collective Hamiltonian, with the ingredients, i.e., the deformation-dependent moments of inertia and mass parameters, and the collective potential, determined by using the SCMF solutions as microscopic inputs. Systematic behaviors of the SCMF potential energy surfaces, the corresponding low-energy spectra, electric quadrupole and monopole transition probabilities, and the fluctuations in the triaxial quadrupole deformations indicate evolution of the underlying nuclear structure as functions of the neutron number, that is characterized by a considerable degree of shape mixing. A special attention is paid to the transitional nucleus ${}^{82}\mathrm{Kr}$, which has been recently identified experimentally as an empirical realization of the E(5) critical-point symmetry.