We use molecular dynamics simulations to study the formation and stability of single- and multicomponent lattices in the outer crust of neutron stars. Including an improved treatment for Gaussian charge distributions of ions, we obtain the expressions for the potential and forces arising from electron screened Coulomb interactions using the efficient Ewald sum procedure. Our findings show that. for baryon densities in the outer crust, a pointlike ion treatment cannot fully describe the crystallization behavior. In our work, the usual Coulomb parameter, ${\mathrm{\Gamma }}_C$, along with the screening parameter from an electron polarizable background, $\kappa$, are complemented with an additional parameter, $\eta$, providing information on the finite size of ions. In our approach we find that including beyond-pointlike approaches in screened ion plasmas under the Thomas-Fermi approximation has a strong impact on calculated lattice energetic stability, decreasing crystallization energies per baryon up to $\approx 40\%$ with respect to pointlike interaction and, as a consequence, melting point is displaced to lower temperatures.

The rapidity-dependent directed flow of particles produced in a relativistic heavy-ion collision can be generated in the hydrodynamic expansion of a tilted source. The asymmetry of the pressure leads to a buildup of a directed flow of matter with respect to the collision axis. The experimentally observed ordering of the directed flow of baryons, pions, and antibaryons can be described as resulting from the expansion of a baryon inhomogeneous fireball. An uneven distribution of baryons in the transverse plane leads to a difference in the collective push for protons and antiprotons. Precise measurements of the collective flow of identified particles as a function of rapidity could serve as a strong constraint on mechanism of baryon stopping in the early phase of the collision.

Numerous applications rely on the identification and quantification of fission products with the activation technique, where $\gamma$ rays emitted in the decay are used to estimate the initial activity of the radionuclide of interest. ${}^{130}\mathrm{I}$ is a so-called blocked fission product, which can be produced only directly through fission, a property that makes it particularly attractive for nuclear forensics. A source of ${}^{130}\mathrm{I}$ was produced using a $(p,n)$ reaction on enriched ${}^{130}\mathrm{Te}$ at the Brookhaven Tandem Van de Graaff, and its decay was studied with the Gammasphere at Argonne National Laboratory. Two new levels were identified, and over 25 transitions were added, removed, or replaced in the level scheme with intensity measurements made down to $I_{\gamma }$ = 0.000 66 per 100 decays. The uncertainty on the intensities of the strongest transitions, those that are commonly used to quantify the activity of the radionuclide, was improved by a factor of 2 compared to the previous best assessment, and discrepancies in the literature values were resolved. A detailed angular correlation analysis further permitted the determination of a number of spin assignments for excited levels and mixing ratios for $\gamma$-ray transitions.

The problems related to the existence of the spurious dipole mode (SDM) in self-consistent nuclear-structure models are considered. A method is formulated that allows one to eliminate the coupling of the SDM with the physical modes in the extended random-phase approximation (ERPA) theories, in particular, in the time blocking approximation (TBA), which is a model of the ERPA type. It is shown that the application of this method in realistic TBA calculations of the $E1$ excitations gives results which are very close to the results of TBA calculations without using this method if the bare external-field $E1$ operators are replaced by effective ones.

Isomeric states in the neutron-rich nuclei ${}^{111}\mathrm{Zr} [{\mathrm{T}}_{1/2}=0.10\left(7\right)\mu \mathrm{s}], {}^{113}\mathrm{Nb} [{\mathrm{T}}_{1/2}=0.7\left(4\right)\mu \mathrm{s}], {}^{115}\mathrm{Mo} [{\mathrm{T}}_{1/2}=46\left(3\right)\mu \mathrm{s}]$ were first identified at the Radioactive Ion Beam Factory (RIBF) of RIKEN by using in-flight fission and fragmentation of a ${}^{238}\mathrm{U}$ beam at an energy of 345 MeV/u. This is a brief report of the $\gamma$ transitions de-exciting from isomeric states and half-lives measurements, which provides the first spectroscopy in the nuclear region of prolate-to-oblate shape-phase transition around mass A $\approx 110$.

The alpha decay of ${}^{247}\mathrm{Cm}$ was studied fifty years ago using a 1.6 Bq source containing 99.4% ${}^{247}\mathrm{Cm}$, and levels in ${}^{243}\mathrm{Pu}$ were deduced. Using the same source, $\gamma$-ray spectra were measured with a more efficient Ge detector. A $\gamma$-ray spectrum was also measured in coincidence with $\alpha$ particles for a period of two months and has 80 times more counts than the previously published spectrum. $\gamma$-ray energies were determined with higher precision and four new $\gamma$ rays were identified. A new high-energy $\gamma$ ray of 564.5 keV was observed, which is interpreted as a transition between a level at 564.5 keV and the ground state of ${}^{243}\mathrm{Pu}$. The 564.5-keV level has been tentatively assigned to the $7/2^{-}\left[743\right]$ Nilsson state.

Background: An isoscalar $pn$ pair is expected to emerge in nuclei that have similar proton and neutron numbers and it may be a candidate for a deuteron “cluster.” There is, however, no experimental evidence for it.

Purpose: The purpose of this paper is to construct a new reaction model for the $(p,pd)$ reaction including the deuteron breakup in the elementary process and the deuteron reformation by the final-state interactions. How these processes contribute to the observables of the reaction is investigated.

Methods: The distorted wave impulse approximation is extended twofold. The elementary processes of the $(p,pd)$, i.e., the $p\text{−}d$ elastic scattering and the $d(p,p)pn$ reaction, are described with an impulse picture employing a nucleon-nucleon effective interaction. The three-body scattering waves in the final state of the $(p,pd)$ reaction are calculated with the continuum-discretized coupled-channels method. The triple-differential cross section (TDX) of the $(p,pd)$ reaction is calculated with the new model.

Results: The elementary processes are described reasonably well with the present model. As for the $(p,pd)$ reaction, the deuteron reformation can either increase or decrease the TDX height depending on the interference between the elastic and breakup channels of deuteron, while the back-coupling effect always decreases it.

Conclusions: It is shown that the deuteron reformation significantly changes the TDX of the $(p,pd)$ reaction through the interference. It is important to include this process to quantitatively discuss the $(p,pd)$ cross sections in view of the deuteron formation in nuclei. For more quantitative discussion regarding the experimental data, further improvement will be necessary.

We examine the role of the $\mathrm{U}{\left(1\right)}_A$ anomaly in a parity doublet model of nucleons which include the chiral variant and invariant masses. Our model expresses the $\mathrm{U}{\left(1\right)}_A$ anomaly by the Kobayashi-Maskawa-'t Hooft (KMT) interaction in the mesonic sector. After examining the roles of the KMT term in vacuum, we discuss its impacts on nuclear equations of state (EOS). The $\mathrm{U}{\left(1\right)}_A$ anomaly increases the masses of the ${\eta }^{\prime }$ and $\sigma$ mesons and enhances the chiral symmetry breaking. Also, the $\mathrm{U}{\left(1\right)}_A$ anomaly enlarges the energy difference between chiral symmetric and symmetry broken vacuum; in turn, the chiral restoration at high density adds a larger energy density (often referred as a bag constant) to EOSs than in the case without the anomaly, leading to softer EOSs. Including these $\mathrm{U}{\left(1\right)}_A$ effects, we update the previously constructed unified equations of state that interpolate the nucleonic EOS at $n_B\le 2n_0$ ($n_0=0.16{\mathrm{fm}}^{-3}$; nuclear saturation density) and quark EOS at $n_B\ge 5n_0$. The unified EOS is confronted with the observational constraints on the masses and radii of neutron stars. The softening of EOSs associated with the $U$(1) anomaly reduces the overall radii, relaxing the previous constraint on the chiral invariant mass $m_0$. Including the attractive nonlinear $\rho \text{−}\omega$ coupling for the reduced slope parameter in the symmetry energy, our new estimate is $400\mathrm{MeV}\le m_0\le 700\mathrm{MeV}$, with $m_0$ smaller than our previous estimate by $\approx$200 MeV.

The production of the $K_S^0$ meson in high multiplicity $pp$ collisions at $\sqrt{s}=$ 13 TeV is investigated considering the hybrid formalism and the solution of the running coupling Balitsky-Kovchegov (BK) equation. The associated cross section is estimated and compared with the experimental data for the transverse momentum spectrum. Moreover, we analyze the self-normalized yields of $K_S^0$ mesons as a function of the multiplicity of coproduced charged hadrons and demonstrate that a steep increasing is theoretically predicted. A comparison with the ALICE data is presented considering two distinct solutions of the BK equation.

Systematic differences exist between values of the proton's electric form factors in the low-$Q^2$ region extracted by different experimental and theoretical groups, though they are all making use of basically the same electron-proton scattering data. To try to understand the source of these differences, we make use of the analytically well-behaved rational ($N=1, M=1$) function, a predictive function that can be reasonably used for extrapolations at $Q^2\to 0$. First, we test how well this deceptively simple two-parameter function describes the extremely complex and state-of-the-art dispersively improved chiral effective field theory calculations. Second, we carry out a complete re-analysis of the 34 sets of electron-proton elastic scattering cross-section data of the Mainz A1 Collaboration with its unconstrained 31 normalization parameters up to $Q^2{=0.5(\mathrm{GeV}/c)}^2$. We find that subtle shifts in the normalization parameters can result in relatively large changes in the extracted physical qualities. In conclusion, we show that by simply using a well-behaved analytic function, the apparent discrepancy between recent form-factor extractions can be resolved.

The past two decades have yielded several new measurements and reanalysis of older measurements of the neutron lifetime. These have led to a 4.4 standard deviation discrepancy between the most precise measurements of the neutron decay rate producing protons in cold neutron beams and the most precise lifetime measured in neutron storage experiments. Measurements using different techniques are important for investigating whether there are unidentified systematic effects in any of the measurements. In this paper we report a new measurement using the Los Alamos asymmetric magneto-gravitational trap where the surviving neutrons are counted external to the trap using the fill and dump method. The new measurement gives a free neutron lifetime of ${\tau }_n=876.3{\left(2.4\right)}_{\mathrm{stat}}{\left(0.8\right)}_{\mathrm{syst}}$. Although this measurement is not as precise, it is in statistical agreement with previous results using in situ counting in the same apparatus.

Both the ground [denoted $G_{+}$ ($G_{-}$) for a positive-parity (negative-parity) sequence] and excited ($E{x}_{+}$ and $E{x}_{-}$) alternating-parity bands have been observed in a few octupole-deformed even-even nuclei. Taking ${}^{148}\mathrm{Ce}$ as an example, the restored symmetries for the observed bands are investigated by constructing a symmetry group $\{E,{\mathcal{R}}_1,{\mathcal{R}}_2,{\mathcal{R}}_3,{\mathcal{S}}_1,{\mathcal{S}}_2,{\mathcal{S}}_3,\mathcal{P}\}$. All possible wave functions belonging to eight group representations have been analyzed. It is found that, to agree with the observed transitions in ${}^{148}\mathrm{Ce}, G_{+}$ and $E{x}_{+}$ should belong to the same group representation $(+1,+1,+1,+1,+1,+1,+1,+1)$, while $G_{-}$ and $E{x}_{-}$ should belong to the representation $(+1,-1,-1,+1,+1,+1,-1,-1)$. A new understanding of the symmetries for the observed excited band is provided, and a different value of simplex quantum number is proposed. From another perspective, the wave functions of the observed ground and excited bands should be symmetrical and antisymmetrical, respectively, which exactly correspond to two modes of symmetry restoration.

We investigate the proton emission from halo nuclei induced by intense x-ray lasers within the framework of a nonperturbative quantum $S$-matrix approach. We have analytically deduced the angular differential as well as the total multiphoton rates of the proton emissions. For a linearly polarized x-ray laser field, we find that the angular distributions of proton emission sensitively depend on the laser frequency and show an interesting petal structure with increasing laser frequency as well as the number of absorbed photons. Meanwhile, we find the Coulomb repulsion potential between the proton and the remainder nucleus has a strong hindering effect on the total multiphoton rates of the proton emissions and leads to the blueshifts of the multiphoton transition frequency. Moreover, the polarization effects of laser fields on total rates of proton emission have also been addressed. We find that the polarized ellipticity corresponding to the maximum of the total rates depends on the laser frequency showing a transition from perturbative to nonperturbative proton emission. The underlying mechanism of the above findings is uncovered, and some implications are discussed.

We investigate the deuteron-triton (DT) fusion in a three-body collision system of $\mathrm{T}\mu$ (i.e, a muon bound to a triton) impacted by a deuteron in the presence of intense laser fields with a semiclassical (SC) method. In this model, the initial positions and momenta of triton and muon are sampled from microcanonical distribution, and the dynamical process of a deuteron with a given incident kinetic energy colliding with the $\mathrm{T}\mu$ atom is simulated by tracing the classical trajectories in the combined Coulomb potentials and laser fields. At the minimum distance between the deuteron and triton, quantum tunneling through the Coulomb barrier emerges, and the penetrability can be estimated with the Wentzel-Kramers-Brillouin formula. DT nuclear fusion occurs after this quantum tunneling, and the total fusion cross section takes the Gamow form. Within the framework of the SC model, we investigate the charge shielding effect, demonstrating that this effect emerges in the low energy regime, where the impact velocity of the deuteron is smaller than the average velocity of muons in the bound state. Furthermore, the tunneling penetrability is considerably enhanced because the deuteron closely approaches the triton due to the quiver motions of charged nuclei driven by intense laser fields. As a result, the fusion cross section in this in-flight muon catalyzed fusion system can be enhanced by up to six orders of magnitude. Moreover, we calculated the DT fusion sections for a wide range of laser parameters and obtained phase diagrams demonstrating the enhanced DT fusion. Finally, important implications in achieving a large number of fusion reactions catalyzed by muons assisted by laser fields are discussed.

Elastic-scattering angular distribution for the weakly bound nucleus ${}^6\mathrm{Li}$ on the deformed rare-earth ${}^{159}\mathrm{Tb}$ target nucleus has been measured at energies around the Coulomb barrier. The elastic-scattering cross sections for this reaction consist of inelastic contributions from low-lying excited states of ${}^{159}\mathrm{Tb}$. The pure elastic cross sections have been extracted from the admixture of elastic and inelastic data. The optical model potential parameters for the system have been obtained from the extracted pure elastic-scattering cross sections. Coupled-channel calculations have been performed with this set of potential parameters, to compare the theoretical and experimental inelastic-scattering cross sections. The work has been extended to obtain the spectroscopic factor for ${}^{158}\mathrm{Tb}+n$ configuration from the experimental $1n$-pickup data.

The extremely neutron-deficient isotope ${}^{179}\mathrm{Au}$ has been studied by a combination of in-beam $\gamma$-ray and isomeric-decay spectroscopy. For in-beam spectroscopy, the recoil-isomer tagging technique was employed, using the known 3/$2^{-}, T_{1/2}=328$ ns isomer. A new rotational band, associated with the unfavored signature band of the $1h_{9/2}\oplus 2f_{7/2}$ proton-intruder configuration, was revealed. A previously unknown, high-spin isomeric state with an excitation energy of 1743(17) keV and $T_{1/2}=2.16\left(8\right)\mathrm{\mu s}$ was discovered. Five decay paths were identified, some of them feeding previously unknown non-yrast excited states, associated with the $1i_{13/2}$ proton-intruder configuration. Calculations based on the particle-plus-triaxial-rotor model were performed to interpret the data. On the basis of these calculations, the new $1h_{9/2}\oplus 2f_{7/2}$ rotational band is interpreted as due to triaxial deformation of the underlying configuration with ${\beta }_2\approx 0.26$ and $\gamma \approx {27}^{\circ }$. Observed non-yrast states of the positive-parity $1i_{13/2}$ intruder configuration are interpreted as due to triaxial deformation with ${\beta }_2\approx 0.26$ and $\gamma \approx {20}^{\circ }$.

Baryon annihilations during the hadronic stage of heavy-ion collisions affects final-state baryon and antibaryon yields and final-state correlations of baryons and antibaryons. Understanding annihilation is important for addressing questions about the chemistry at the beginning of the hadronic stage and for interpreting charge-balance correlations involving baryons. Here, charge balance functions, using protons and antiprotons binned by relative momentum, rapidity, and azimuthal angle are shown to clarify the amount of annihilation in the hadronic stage. This enables a more accurate extraction of the baryo-chemistry at the beginning of the hadronic stage. Understanding annihilation is also crucial if charge balance correlations are to be used to infer the chemistry of the earliest stages of a heavy-ion collision. Calculations are presented based on microscopic simulations of the hadronic stage coupled to a hydrodynamic description of the earlier stage, along with a detailed modeling of correlations of protons and antiprotons, known as charge-balance functions.

Inspired by a recent Letter [S. R. Beane et al., Phys. Rev. Lett. 122, 102001 (2019)], the entanglement generated in the elastic $S$-wave scattering of $p+{}^3\mathrm{He}$ and $n+{}^3\mathrm{H}$ is studied, where the proton, neutron, ${}^3\mathrm{He}$, and ${}^3\mathrm{H}$ are all regarded as qubits. To deal with the Coulomb interaction between the proton and ${}^3\mathrm{He}$, we derive the entanglement power, a physical quantity that measures the average entanglement generated by a scattering process, for charged qubits within the screening method. The entanglement power in the aforementioned two few-nucleon scatterings is found to be generally much smaller than that in the $S$-wave $n+p$ scattering at low energies, with the corresponding cluster effective field theories possessing an enhanced approximate $\text{SU}{\left(2\right)}_1\otimes \text{SU}{\left(2\right)}_2$ symmetry at leading order. Our study suggests that the entanglement generation capacities of effective interactions between nucleons and light nuclei could be more suppressed than realistic nucleon-nucleon interactions at low energies.

A digital quantum simulation for the extended Agassi model is proposed using a quantum platform with eight trapped ions. The extended Agassi model is an analytically solvable model including both short range pairing and long range monopole-monopole interactions with applications in nuclear physics and in other many-body systems. In addition, it owns a rich phase diagram with different phases and the corresponding phase transition surfaces. The aim of this work is twofold: on one hand, to propose a quantum simulation of the model at the present limits of the trapped ions facilities and, on the other hand, to show how to use a machine learning algorithm on top of the quantum simulation to accurately determine the phase of the system. Concerning the quantum simulation, this proposal is scalable with polynomial resources to larger Agassi systems. Digital quantum simulations of nuclear physics models assisted by machine learning may enable one to outperform the fastest classical computers in determining fundamental aspects of nuclear matter.