A theoretical method is proposed to describe the ground and excited cluster states of atomic nuclei. The method makes use of the equation of motion of the Gaussian wave packets to generate the basis wave functions incorporating various cluster configurations. The generated basis wave functions are superposed to diagonalize the Hamiltonian. This method is regarded as the generator coordinate method which uses the real time as the generator coordinate. As a application of our proposed method, we present the benchmark calculation for the $3\alpha$ system. We show that our proposed method works efficiently and yields the results consistent with or better than the other cluster models. We have also discussed briefly the structure of the excited $0^{+}$ and $1^{-}$ states.

A multiphase transport (AMPT) model has been successful in explaining a wide range of observables in relativistic heavy ion collisions. In this work, we implement a newer set of free proton parton distribution functions and an impact parameter-dependent nuclear shadowing in the AMPT model. After refitting the parameters of the two-component initial condition model to the experimental data on $pp$ and $p\overline{p}$ total and inelastic cross sections from $\sqrt{s}\sim$ 4 GeV to 13 TeV, we study particle productions in $pp$ and $AA$ collisions. We show that the updated AMPT model with string melting can reasonably describe the overall particle yields and transverse momentum spectra for both $pp$ and $AA$ collisions at RHIC and LHC energies after we introduce a nuclear scaling of the minijet transverse momentum cutoff for $AA$ collisions at LHC energies that is motivated by the color glass condensate. Since heavy flavor and $\mathrm{high}-p_{\mathrm{T}}$ particles are produced by perturbative-QCD processes and thus directly depend on parton distribution functions of nuclei, the updated AMPT model is expected to provide a more reliable description of these observables.

A new mechanism of photon emission in the quark-gluon plasma is proposed. Photon dispersion relation in the presence of the $CP$-odd topological regions generated by the chiral anomaly acquires an imaginary mass. It allows photon radiation through the decay $q\to q\gamma$ and annihilation $q\overline{q}\to \gamma$ processes closely related to the chiral Cherenkov radiation. Unlike previous proposals this mechanism does not require an external magnetic field. The differential photon emission rate per unit volume is computed and shown to be comparable to the rate of photon emission in conventional processes.

The series of articles [Ann. Phys. 345, 73 (2014) and Ann. Phys. 356, 57 (2015)] devoted to excited-state quantum phase transitions (ESQPTs) in systems with $f=2$ degrees of freedom is continued by studying the interacting boson model of nuclear collective dynamics as an example of a truly many-body system. The intrinsic Hamiltonian formalism with angular momentum fixed to $L=0$ is used to produce a generic first-order ground-state quantum phase transition with an adjustable energy barrier between the competing equilibrium configurations. The associated ESQPTs are shown to result from various classical stationary points of the model Hamiltonian, whose analysis is more complex than in previous cases because of (i) a nontrivial decomposition to kinetic and potential energy terms and (ii) the boundedness of the associated classical phase space. Finite-size effects resulting from a partial separability of both degrees of freedom are analyzed. The features studied here are inherent in a great majority of interacting boson systems.

We explore the situation of intertwined quantum phase transitions (IQPTs), for which a QPT involving a crossing of two configurations is accompanied by a shape evolution of each configuration with its own separate QPT. We demonstrate the relevance of IQPTs to the Zr isotopes, with such coexisting Type I and Type II QPTs, and ground state shapes changing from spherical to prolate axially deformed and finally to $\gamma$-unstable. Evidence for this scenario is provided by a detailed comparison with experimental data, using a definite symmetry-based conceptual framework.

$0_2^{+}$ bands in ${}^{98}\mathrm{Sr}$ and ${}^{100}\mathrm{Zr}$, populated in spontaneous fission of ${}^{248}\mathrm{Cm}$ and ${}^{252}\mathrm{Cf}$, have been studied using the Eurogam2 and Gammasphere arrays. Phenomenological classification of excited $0^{+}$ levels in even-even nuclei of the $A\approx 100$ region into four categories is presented and an interpretation for each category is proposed. Highly deformed $0_1^{+}$ ground states and low-energy $0_2^{+}$ levels in both nuclei are probably due to the 2p-2h excitation of two neutrons from the $9/2^{+}\left[404\right]$ extruder to the low-$\mathrm{\Omega }$ prolate and the $11/2^{-}\left[505\right]$ oblate orbitals originating from the $h_{11/2}$ shell, respectively. Candidates for $0^{+}, \beta$ vibrational states in $A\approx 100$ region are suggested at $\mathrm{N}>60$.

The behavior of the collective rotor in the chiral motion of triaxially deformed nuclei is investigated using the particle rotor model by transforming the wave functions from the $K$ representation to the $R$ representation. The energy spectra of the doublet bands and their energy differences as functions of the triaxial deformation are first examined and then the angular momentum components of the rotor, proton, neutron, and the total system are investigated. Moreover, the probability distributions of the rotor angular momentum ($R$ plots) and their projections onto the three principal axes ($K_R$ plots) are analyzed. The evolution of the chiral mode from a chiral vibration at the low spins to a chiral rotation at high spins is illustrated at triaxial deformations $\gamma ={20}^{\circ }$ and ${30}^{\circ }$.

While superfluidity is accurately grasped with a state that explicitly breaks the particle number symmetry, a precise description of phenomena such as the particle transfer during heavy-ion reactions can only be achieved by considering systems with good particle numbers. We investigate the possibility to restore particle number in many-body dynamical problems by mixing up several time-dependent Hartree-Fock-Bogolyubov (TDHFB) trajectories. In our approach, each trajectory is independent from the others and the quantum mixing between trajectories is deduced from a variational principle. The associated theory can be seen as a simplified version of the multiconfiguration TDHFB (MC-TDHFB) theory. Its accuracy to tackle the problem of symmetry restoration in dynamical problems is illustrated for the case of two superfluid systems that exchange particles during a short time. In Phys. Rev. C 97, 034627 (2018), using a schematic model where two systems initially described by a pairing Hamiltonians are coupled during a short contact time, it was demonstrated that statistical mixing of TDHFB trajectories can only qualitatively describe the transfer process and that a fully quantum treatment is mandatory. We show here that the present MC-TDHFB approach gives an excellent agreement with the exact solution when the two superfluids are the same (symmetric case) or different (asymmetric case) and from weak to strong interaction strength. Finally, we discuss the benefits and bottleneck of this method in view of its application to realistic systems.

Experimental data concerning binary events in peripheral collisions for the systems ${}^{93}\mathrm{Nb}+{}^{93}\mathrm{Nb}$ and ${}^{93}\mathrm{Nb}+{}^{116}\mathrm{Sn}$ at 38 MeV/nucleon, collected with the Fiasco setup, are compared with calculations performed with the dynamic code AMD, coupled with the statistical code Gemini used as an afterburner. The comparison focuses on the properties of the quasiprojectile (QP) and on the total multiplicities of the emitted light charged particles. A good reproduction of the average mass ratio, charge $Z$, and center-of-mass angle of the QP is obtained in the examined impact parameter range ($b\approx 7–12\mathrm{fm}$). Concerning the light charged particles, a general agreement is found for the total emitted charge, while some discrepancy remains for the multiplicities of the various species, especially for the protons, which are always overestimated by the calculations.

We report the energy dependence of mid-rapidity (anti-)deuteron production in Au+Au collisions at $\sqrt{s_{\text{NN}}}=7.7$, 11.5, 14.5, 19.6, 27, 39, 62.4, and 200 GeV, measured by the STAR experiment at the BNL Relativistic Heavy Ion Collider. The yield of deuterons is found to be well described by the thermal model. The collision energy, centrality, and transverse momentum dependence of the coalescence parameter $B_2$ are discussed. We find that the values of $B_2$ for antideuterons are systematically lower than those for deuterons, indicating that the correlation volume of antibaryons is larger than that of baryons at $\sqrt{s_{\text{NN}}}$ from 19.6 to 39 GeV. In addition, values of $B_2$ are found to vary with collision energy and show a broad minimum around $\sqrt{s_{\text{NN}}}=20–40$ GeV, which might imply a change of the equation of state of the medium in these collisions.

We have developed a novel ab initio Gamow in-medium similarity renormalization group (Gamow IMSRG) in the complex-energy Berggren framework. The advanced Gamow IMSRG is capable of describing the resonance and nonresonant continuum properties of weakly bound and unbound nuclear many-body systems. As test grounds, carbon and oxygen isotopes have been calculated with chiral two- and three-nucleon forces from the effective field theory. Resonant states observed in the neutron-dripline ${}^{24}\mathrm{O}$ are well reproduced. The halo structure of the known heaviest Borromean nucleus ${}^{22}\mathrm{C}$ is clearly seen by calculating the density distribution in which the continuum $s$ channel plays a crucial role. Furthermore, we predict low-lying resonant excited states in ${}^{22}\mathrm{C}$. The Gamow IMSRG provides tractable ab initio calculations of weakly bound and unbound open quantum systems.

A fully self-consistent renormalized random-phase approximation is constructed based on the self-consistent Hartree-Fock mean field plus exact pairing solutions (EP). This approach exactly conserves the particle number and restores the energy-weighted sum rule, which is violated in the conventional renormalized particle-hole random-phase approximation for a given multipolarity. The numerical calculations are carried out for several light-, medium-, and heavy-mass nuclei such as ${}^{22}\mathrm{O}$, ${}^{60}\mathrm{Ni}$, and ${}^{90}\mathrm{Zr}$ by using the effective MSk3 interaction. To study the pygmy dipole resonance (PDR), the calculations are also performed for the two light and neutron-rich ${}^{24,28}\mathrm{O}$ isotopes, whose PDRs are known to be dominant. The results obtained show that the inclusion of ground-state correlations beyond the random-phase approximation (RPA) by means of the occupation numbers obtained from the EP affects the RPA solutions within the whole mass range, although this effect decreases with increasing the mass number. At the same time, the antipairing effect is observed via a significant reduction of pairing in neutron-rich nuclei. The enhancement of PDR is found in most neutron-rich nuclei under consideration within our method.

We investigate possibility of emission of bremsstrahlung photons in nuclear reactions with hypernuclei for the first time. A new model of bremsstrahlung emission which accompanies interactions between $\alpha$ particles and hypernuclei is constructed, where a new formalism for magnetic moments of nucleons and a hyperon inside a hypernucleus is added. To start calculations, we choose $\alpha$ decay of normal nucleus ${}^{210}\mathrm{Po}$ and hypernucleus ${}_{\mathrm{\Lambda }}{}^{211}\mathrm{Po}$. We find that (1) emission for the hypernucleus ${}_{\mathrm{\Lambda }}{}^{211}\mathrm{Po}$ is larger than for the normal nucleus ${}^{210}\mathrm{Po}$ and (2) the difference between these spectra is small. We propose a way to find the hypernuclei where the role of hyperon is the most essential in emission of the bremsstrahlung photons during $\alpha$ decay. As demonstration of such a property, we show that spectra for the hypernuclei ${}_{\mathrm{\Lambda }}{}^{107}\mathrm{Te}$ and ${}_{\mathrm{\Lambda }}{}^{109}\mathrm{Te}$ are essentially larger than the spectra for the normal nuclei ${}^{106}\mathrm{Te}$ and ${}^{108}\mathrm{Te}$. Such a difference is explained by additional contribution of emission to the full bremsstrahlung, which is formed by magnetic moment of hyperon inside hypernucleus. The bremsstrahlung emission formed by such a mechanism is of magnetic type. A new formula for fast estimations of bremsstrahlung spectra for even-even hypernuclei is proposed, where the role of the magnetic moment of the hyperon of the hypernucleus in formation of bremsstrahlung emission is shown explicitly. Then we applied our model to study bremsstrahlung emission in $\alpha$ decay of light hypernuclei ${}_{\mathrm{\Lambda }}{}^{10}\mathrm{Be}$ and ${}_{\mathrm{\Lambda }}{}^{10}\mathrm{B}$ (which was the subject of investigations at the Nuclotron at JINR, Dubna). Such an analysis opens the possibility of new experimental study of properties of the hypernuclei via bremsstrahlung study.

The double-slit experiment has become a classic thought experiment for its clarity in expressing the central puzzle of quantum mechanics—wave-particle complementarity. Such wave-particle duality continues to be challenged and investigated in a broad range of entities with electrons, neutrons, helium atoms, ${\mathrm{C}}_{60}$ fullerenes, Bose-Einstein condensates, and biological molecules. In this Rapid Communication, we present a double-slit scenario at Fermi scale with new entities—coherent photon products in heavy-ion collisions. Virtual photons from the electromagnetic fields of relativistic heavy ions can fluctuate to quark-antiquark pairs, scatter off a target nucleus, and emerge as vector mesons. The two colliding nuclei can take turns to act as targets, forming a double-slit interference pattern. Furthermore, the “which-way” information can be partially solved using sufficiently-high multiplicity heavy-ion collisions so that the reaction plane can be determined, which demonstrates the complementary principle, a key concept of quantum mechanics.

When traversing the QCD medium, high-$p_{\perp }$ partons lose energy, which is typically measured by suppression, and predicted by various energy-loss models. A crucial test of different energy-loss mechanisms is their functional dependence on the length of traversed medium (i.e., path-length dependence). The upcoming experimental measurements will, for the first time, generate data that may allow to clearly assess this dependence, in particular, by comparing results from Pb $+$ Pb collisions with future measurements in smaller systems. However, to perform such a test, it is crucial to choose an optimal observable. To address this, we here use both analytical and numerical analyses to propose a novel—simple, yet accurate and robust—observable for assessing the path-length dependence of the energy loss. Our numerical results show that, by using this observable, different (underlying) energy-loss mechanisms may be directly differentiated from the experimental data, which is, in turn, crucial for understanding the properties of the created QCD medium.

Inelastic neutron scattering was used to study the low-lying nuclear structure of ${}^{132}\mathrm{Xe}$. A comprehensive level scheme is presented, as well as new level lifetimes, multipole mixing ratios, branching ratios, and transition probabilities. Comparisons of these data as well as previously measured $E2$ strengths and $g$ factors are made with new shell-model calculations for ${}^{132,134,136}\mathrm{Xe}$ to explore the emergence of collectivity in the Xe isotopes with $N<82$ near the closed shell.

Elastic scattering of a radioactive neutron-rich boron isotope, ${}^{12}\mathrm{B}$, has been measured for the first time. Angular distributions for the elastic scattering of ${}^{12}\mathrm{B}+{}^{58}\mathrm{Ni}$ have been measured at ${\mathit{E}}_{\mathrm{Lab}}=30.0$ and 33.0 MeV, which are just above the Coulomb barrier (${\mathit{V}}_{\mathrm{B}}=24$ MeV). The obtained angular distributions were analyzed in terms of the large-scale coupled channel (CC) and coupled reaction channel (CRC) calculations, where several inelastic transitions for the target, as well as the most relevant transfer reactions, have been included in the coupling matrix elements. The roles of the spin reorientation and spin-orbit interaction in the reaction mechanism were also investigated. The one-neutron transfer reaction through a coupled reaction calculation had some effect on the elastic scattering of the system studied.

Electromagnetic observables are able to give insight into collective and emergent features in nuclei, including nuclear clustering. These observables also provide strong constraints for ab initio theory, but comparison of these observables between theory and experiment can be difficult due to the lack of convergence for relevant calculated values, such as $E2$ transition strengths. By comparing the ratios of $E2$ transition strengths for mirror transitions, we find that a wide range of ab initio calculations give robust and consistent predictions for this ratio. To experimentally test the validity of these ab initio predictions, we performed a Coulomb excitation experiment to measure the $B(E2;3/2^{-}\to 1/2^{-})$ transition strength in ${}^7\mathrm{Be}$ for the first time. A $B(E2;3/2^{-}\to 1/2^{-})$ value of $26{\left(6\right)}_{\mathrm{stat}}{\left(3\right)}_{\mathrm{syst}}{e}^2{\mathrm{fm}}^4$ was deduced from the measured Coulomb excitation cross section. This result is used with the experimentally known ${}^7\mathrm{Li}B(E2;3/2^{-}\to 1/2^{-})$ value to provide an experimental ratio to compare with the ab initio predictions. Our experimental value is consistent with the theoretical ratios within $1\sigma$ uncertainty, giving experimental support for the value of these ratios. Further work in both theory and experiment can give insight into the robustness of these ratios and their physical meaning.

A widely accepted practice for treating deuteron breakup in $A(d,p)B$ reactions relies on solving a three-body $A+n+p$ Schrödinger equation with pairwise $A\text{−}n$, $A\text{−}p$ and $n\text{−}p$ interactions. However, it was shown in Phys. Rev. C 89, 024605 (2014) that projection of the many-body $A+2$ wave function into the three-body $A+n+p$ channel results in a complicated three-body operator that cannot be reduced to a sum of pairwise potentials. It contains explicit contributions from terms that include interactions between the neutron and proton via excitation of the target $A$. Such terms are normally neglected. We estimate the first-order contribution of these induced three-body terms and show that applying the adiabatic approximation to solving the $A+n+p$ model results in a simple modification of the two-body nucleon optical potentials. We illustrate the role of these terms for the case of ${}^{40}\mathrm{Ca}(d,p){}^{41}\mathrm{Ca}$ transfer reactions at incident deuteron energies of 11.8, 20, and 56 MeV, using several parametrizations of nonlocal optical potentials.

We present results for the quasielastic weak production of $\mathrm{\Lambda }$ and $\mathrm{\Sigma }$ hyperons induced by $\overline{\nu }$ scattering off nuclei in the kinematical region of interest for accelerator neutrino experiments. We employ realistic hole spectral functions and we describe the propagation of the hyperons in the nuclear medium by means of a Monte Carlo cascade. The latter strongly modifies the kinematics and the relative production rates of the hyperons, leading to a nonvanishing ${\mathrm{\Sigma }}^{+}$ cross section, to a sizable enhancement of the $\mathrm{\Lambda }$ production and to a drastic reduction of the ${\mathrm{\Sigma }}^0$ and ${\mathrm{\Sigma }}^{-}$ distributions. We also compute the quasielastic weak ${\mathrm{\Lambda }}_c$ production cross section, paying special attention to estimate the uncertainties induced by the model dependence of the vacuum $n\to {\mathrm{\Lambda }}_c$ weak matrix element. In this regard, the recent BESIII measurements of the branching ratios of ${\mathrm{\Lambda }}_c\to \mathrm{\Lambda }{l}^{+}{\nu }_l$ ($l=e,\mu$) are used to benchmark the available theoretical predictions.