Atomic nuclei are important laboratories for exploring and testing new insights into the universe, such as experiments to directly detect dark matter or explore properties of neutrinos. The targets of interest are often heavy, complex nuclei that challenge our ability to reliably model them (as well as quantify the uncertainty of those models) with classical computers. Hence there is great interest in applying quantum computation to nuclear structure for these applications. As an early step in this direction, especially with regards to the uncertainties in the relevant quantum calculations, we develop circuits to implement variational quantum eigensolver (VQE) algorithms for the Lipkin-Meshkov-Glick model, which is often used in the nuclear physics community as a testbed for many-body methods. We present quantum circuits for VQE for two and three particles and discuss the construction of circuits for more particles. Implementing the VQE for a two-particle system on the IBM Quantum Experience, we identify initialization and two-qubit gates as the largest sources of error. We find that error mitigation procedures reduce the errors in the results significantly, but additional quantum hardware improvements are needed for quantum calculations to be sufficiently accurate to be competitive with the best current classical methods.

We perform coincidence measurements between α particles and γ rays from a ${}^{233}\mathrm{U}$ source to determine the half-lives of the excited state in a ${}^{229}\mathrm{Th}$ nucleus. We first prove that the half-lives of 42.43- and 164.53-keV states are consistent with literature values, whereas that of the 97.14-keV state [93(7) ps] deviates from a previously measured value [147(12) ps]. The half-lives of 71.83- and 163.25-keV states are determined for the first time. Based on the obtained half-lives and the Alaga rule, we estimate the radiative half-life of the low-energy isomeric state $\left({}^{229m}\mathrm{Th}\right)$ to be $5.0\left(11\right)\times {10}^3$ s, which is one of the key parameters for the frequency standard based on ${}^{229}\mathrm{Th}$.

Nucleon resonance contributions to the inclusive proton $F_2$ and $F_L$ structure functions are computed from resonance electroexcitation amplitudes in the mass range up to 1.75 GeV extracted from CLAS exclusive meson electroproduction data, taking into account interference between different excited nucleon states. The resonance contributions are compared with inclusive proton structure functions evaluated from $(e,e^{\prime }X)$ cross section data and the longitudinal to transverse cross section ratio. Contributions from isospin-1/2 and -3/2 resonances remain substantial over the entire range of photon virtualities $Q^2\lesssim 4{\mathrm{GeV}}^2$, where their electroexcitation amplitudes have been obtained, and their $Q^2$ evolution displays pronounced differences in the first, second, and third resonance regions. We compare the structure functions in the resonance region with those computed from parton distributions fitted to deep-inelastic scattering data, and extrapolated to the resonance region, providing new quantitative assessments of quark-hadron duality in inclusive electron-proton scattering.

Low-lying states of ${}^{98}\mathrm{Cd}$ have been populated by the two-nucleon removal reaction (${}^{100}\mathrm{In},{}^{98}\mathrm{Cd}+\gamma$) and studied using in-beam $\gamma$-ray spectroscopy at the Radioactive Isotope Beam Factory at RIKEN. Two new $\gamma$ transitions were identified and assigned as decays from a previously unknown state. This state is suggested to be based on a $\pi 1g_{9/2}^{-1}2p_{1/2}^{-1}$ configuration with $J^{\pi }=5^{-}$. The present observation extends the systematics of the excitation energies of the first $5^{-}$ state in $N=50$ isotones toward ${}^{100}\mathrm{Sn}$. The determined energy of the $5^{-}$ state in ${}^{98}\mathrm{Cd}$ continues a smooth trend along the $N=50$ isotones. The systematics are compared with shell-model calculations in different model spaces. Good agreement is achieved when considering a model space consisting of the $\pi (1f_{5/2}, 2p_{3/2}, 2p_{1/2}, 1g_{9/2}$) orbitals. The calculations with a smaller model space omitting the orbitals below the $Z=38$ subshell could not reproduce the experimental energy difference between the ground and first $5^{-}$ states in $N=50$ isotones, because proton excitations across $Z=38$ subshell yield a large amount of correlation energy that lowers the ground states.

The hot nucleus ${}^{171}\mathrm{Yb}$ is investigated by the covariant density functional theory with the PC-PK1 effective interaction. The thermodynamic quantities are evaluated with the canonical ensemble theory. The pairing correlations is treated by the shell-model-like approach, in which the particle numbers are conserved strictly and in which the blocking effect is handled exactly. An S-shaped heat capacity versus temperature of ${}^{171}\mathrm{Yb}$ appears. It has been studied in terms of the blocking effect, the single-particle levels, the pairing gap, and defined seniority components, and compared to the heat capacity of ${}^{172}\mathrm{Yb}$. The pairing transition from the superfluid state to the normal state can result in the S-shaped heat capacity of ${}^{172}\mathrm{Yb}$ where the one-pair-broken and two-pair-broken states dominate, while the single-particle level structure near the Fermi surface is associated with the S-shaped heat capacity of ${}^{171}\mathrm{Yb}$. For odd-$A$ nuclei, although the one-pair-broken and two-pair-broken states still contribute, the pairing gap and the pairing transition is relatively weak. The S-shaped heat capacity could be affected due to the blocking of the single-particle level near the Fermi surface.

We investigate the bound state ${\beta }^{-}$ decay of highly ionized atoms, in which the decay electron remains in a bound atomic state rather than being emitted into the continuum. A survey of 3344 nuclei is performed in order to search possible bound state ${\beta }^{-}$ decay nuclei. We find that, for candidates ${}^{163}\mathrm{Dy}$, ${}^{193}\mathrm{Ir}$, ${}^{194}\mathrm{Au}$, ${}^{202}\mathrm{Tl}$, ${}^{205}\mathrm{Tl}$, ${}^{215}\mathrm{At}$, ${}^{222}\mathrm{Rn}$, ${}^{243}\mathrm{Am}$, and ${}^{246}\mathrm{Bk}$, the channel of ${\beta }^{-}$ decay is completely forbidden in the neutral case but can be opened in the bare case. The corresponding bound-state ${\beta }^{-}$ decay half-lives of these nuclei are predicted by using the Takahashi-Yokoi model, which are found to be significantly different from those in the neutral case.

We investigate the implications of initial $3\alpha$ configurations in ${}^{12}\mathrm{C}$ corresponding to different decay modes of its Hoyle state on the penetrability ratios. Considering the second $2^{+}$ (10.03 MeV) state to be a collective excitation of the Hoyle state, the direct $3\alpha$ decay width for the Hoyle state has been calculated using the ratio of the barrier penetration probability of the Hoyle state to the $2^{+}$ state. Semiclassical Wentzel–Kramers–Brillouin (WKB) approximation has been employed to determine the penetrability ratio, resulting in an upper limit on the branching ratio of the direct decay of the Hoyle state in “equal phase-space” ($\mathrm{DD}\varphi$) mode as $\frac{{\mathrm{\Gamma }}_{3\alpha }}{\mathrm{\Gamma }}<3.1\times {10}^{-6}$. However, this limit for “linear chain” (DDL) decay is $\frac{{\mathrm{\Gamma }}_{3\alpha }}{\mathrm{\Gamma }}<2.6\times {10}^{-7}$, which is one order of magnitude smaller than the $\mathrm{DD}\varphi$ decay and the limit for “equal energy” (DDE) decay is $\frac{{\mathrm{\Gamma }}_{3\alpha }}{\mathrm{\Gamma }}<1.5\times {10}^{-5}$, which is greater than both $\mathrm{DD}\varphi$ and DDL decays. It implies that the limit on direct decay probability is strongly dependent on the initial configuration of the $3\alpha$ cluster. A further probe using a bent-arm-like $3\alpha$ initial configuration shows that the direct decay probability is maximum when the angle of the bent arm is $\approx {120}^{\circ }$, an important ingredient for understanding the Hoyle-state structure.

The emission of neutrons and $\gamma$ rays by fission fragments reveal important information about the properties of fragments immediately following scission. The initial fragment properties, correlations between fragments, and emission competition give rise to correlations in neutron-$\gamma$ emission. Recent theoretical and experimental advances have been proposed to explain the mechanism of angular momentum generation in fission, which would result in observable signature in neutron-$\gamma$ emission correlations. In this paper, we present a novel analysis method of neutrons and $\gamma$ rays emitted by fission fragments that allows us to discern structure in the observed correlations. We have analyzed data collected on ${}^{252}\mathrm{Cf}$(sf) at the Chi-Nu array at the Los Alamos Neutron Science Center. Through our analysis of the energy-differential neutron-$\gamma$ multiplicity covariance, we have observed enhanced neutron-$\gamma$ correlations, corresponding to rotational band $\gamma$-ray transitions, at $\gamma$-ray energies of 0.7 and 1.2 MeV. To shed light on the origin of this structure, we compare the experimental data with the predictions of three model calculations. The origin of the observed correlation structure is understood in terms of a positive spin-energy correlation in the generation of angular momentum in fission.

We reanalyze the scaling properties of inclusive quasielastic electron scattering from ${}^{12}\mathrm{C}$ by subtracting from the data the effects of two-particle emission. A model of relativistic meson-exchange currents (MEC) is employed within the mean field theory of nuclear matter, with scalar and vector potentials that induce an effective mass and a vector energy to the nucleons. A new phenomenological quasielastic scaling function is extracted from a selection of the data after the subtraction of the 2p-2h contribution. The resulting superscaling approach with relativistic effective mass (SuSAM*) can be used to compute the genuine quasielastic cross section without contamination of the 2p-2h channel that can then be added separately to obtain the total quasielastic plus two-nucleon emission response.

The decomposition of scattering phase shifts in single-channel systems is extended to coupled-channels systems in the complex scaling method. The present method describes the contribution of the resonant states to the phase shift separately from the background in each channel phase shift of the coupled-channels system. We apply this method to the (${}^3\mathrm{H}+p)+({}^3\mathrm{He}+n)$ model for ${}^4\mathrm{He}$, and show that the decomposition of phase shifts in coupled-channels systems provides useful information about the structure of scattering states.

The neutron-deficient ${}^{119}\mathrm{Ba}$ nucleus has been studied using the ${}^{58}\mathrm{Ni}({}^{64}\mathrm{Zn},2pn)$ reaction and the JUROGAM 3 $\gamma$-ray detector array coupled to the MARA recoil-mass separator setup. One new rotational band and several low-lying states are newly identified. A half-life of $T_{1/2}=0.36\left(2\right)\mu \mathrm{s}$ has been measured for the $5/2^{-}$ bandhead of the $\nu h_{11/2}$ band. The two previously known rotational bands are confirmed, except for the higher part of the +1/2 signature partner of the positive-parity band. Configurations are assigned based on the analysis of the observed quasiparticle alignments whose nature is unveiled by the calculations using the particle number conserving cranked shell model.

High-spin states in ${}^{84}\mathrm{Rb}$ have been studied using the ${}^{76}\mathrm{Ge}({}^{11}\mathrm{B}$, $3n$) reaction at a beam energy of 36 MeV. A pair of nearly degenerate positive-parity doublet bands have been extended and interpreted as candidate chiral doublet bands based on their experimental properties. This interpretation is supported by the triaxial relativistic mean-field theory and the triaxial particle-rotor model calculations. The systematic comparison of the candidate chiral bands in the $A\approx 80$ mass region are also discussed. This work is the first observation of candidate chiral doublet bands in $Z=37$ Rb isotopes and extends the boundaries of the chiral nuclei in the $A\approx 80$ mass region.

We extensively study the system size dependence of nuclear collisions with a multiphase transport model. Previously, certain key parameters for the initial condition needed significantly different values for $pp$ and central $AA$ collisions for the model to reasonably describe the yields and transverse momentum spectra of the bulk matter in those collision systems. Here we scale two key parameters, the Lund string fragmentation parameter $b_L$ and the minijet transverse momentum cutoff $p_0$, with local nuclear thickness functions from the two colliding nuclei. This allows the model to use the parameter values for $pp$ collisions with the local nuclear scaling to describe the system size and centrality dependences of nuclear collisions self-consistently. In addition to providing good descriptions of $pp$ collisions from 23.6 GeV to 13 TeV and reasonable descriptions of the centrality dependence of charged particle yields for Au+Au collisions from $7.7A$ GeV to $200A$ GeV and Pb+Pb collisions at Large Hadron Collider energies, the improved model can now well describe the centrality dependence of the mean transverse momentum of charged particles below $p_{\mathrm{T}}\lesssim 2$ GeV. It works similarly well for smaller systems including $p\mathrm{Pb}$, Cu+Cu and Xe+Xe collisions.

We demonstrate that $\left(n,2n\right)$ reactions are induced by a high-flux pulse of fast neutrons ($\sim {10}^{10}$ neutrons in $\sim 1\mathrm{ns}$) provided from a laser-driven neutron source (LDNS). The maximum energy of the broadband neutrons reaches a few tens MeV. Several kinds of metal targets are exposed to the fast neutrons. As a result, unstable isotopes, such as ${}^{54}\mathrm{Mn}, {}^{58}\mathrm{Co}, {}^{175}\mathrm{Hf}$, and ${}^{196}\mathrm{Au}$ are produced by $\left(n,2n\right)$ reactions and ${}^{180}\mathrm{Hf}^m, {}^{181}\mathrm{Hf}, {}^{56}\mathrm{Mn}, {}^{198}\mathrm{Au}$, and ${}^{60}\mathrm{Co}$ are produced by $(n,\gamma )$ reactions. We evaluate the neutron fluence and energy spectrum using the activation method in conjunction with a time-of-flight measurement. The neutron fluence is determined to be $\left(4.3\pm 0.5\right)\times {10}^8\mathrm{neutrons}/\mathrm{c}{\mathrm{m}}^2$ in the energy range from approximately 8 to 20 MeV at 8-mm downstream of the neutron source. The present scheme provides a method to evaluate high-density neutrons seen in stellar environments, which are expected to be generated from future LDNSs.

It is known that nuclear deformation plays an important role in inducing the halo structure in neutron-rich nuclei by mixing several angular momentum components. While previous theoretical studies on this problem in the literature assume axially symmetric deformation, we here consider nonaxially symmetric deformations. With triaxial deformation, the $\mathrm{\Omega }$ quantum number is admixed in a single-particle wave function, where $\mathrm{\Omega }$ is the projection of the single-particle angular momentum on the symmetric axis, and the halo structure may arise even when it is absent with the axially symmetric deformation. In this way, the area of halo nuclei may be extended when triaxial deformation is considered. We demonstrate this idea using a deformed Woods-Saxon potential for nuclei with neutron number $N=13$ and 43.

The evolution of superheavy nuclei in proton and neutron number is explored by investigating the ground-state shell correction energy in the $Z=112\text{–}126$ and $N=170\text{–}190$ region of the $(Z,N)$ plane. Cuts through the $(Z,N)$-dependent distribution of shell corrections are chosen for constant neutron-proton differences as accessible in $\alpha$-decay chains and varying the neutron number at fixed charge number. A new approach is used, integrating elements of energy-density functional theory into the microscopic-macroscopic method. The topology of the shell correction implies for binding energies a distribution resembling in shape a ridge on a coral reef, formed by the competition of proton and neutron shell closures at $Z=114$ and $Z=120$, and $N=174$ and $N=184$, respectively. ${}^{288}\mathrm{Fl}$ is predicted as the next double magic nucleus after ${}^{208}\mathrm{Pb}$, and ${}^{304}120$ is identified as the most likely candidate for next-to-next double magic nucleus.

Decay protons from excited states in ${}^{21}\mathrm{Na}$ populated through a previously reported ${}^{24}\mathrm{Mg}(p,\alpha ){}^{21}\mathrm{Na}$ transfer reaction [Cha et al., Phys. Rev. C 96, 025810 (2017)] were analyzed to extract the proton branching ratios of the energy levels. By utilizing 31-MeV proton beams from the Holifield Radioactive Ion Beam Facility of Oak Ridge National Laboratory and isotopically enriched ${}^{24}\mathrm{Mg}$ solid targets, the decay protons were detected in coincidence with $\alpha$ particles from the $(p,\alpha )$ reaction using a silicon strip detector array. Proton decay branching ratios of several ${}^{21}\mathrm{Na}$ levels were deduced for the $p0$ and $p1$ decay channels to the ground and first excited states in ${}^{20}\mathrm{Ne}$, respectively.