The multinucleon transfer mechanism in ${}^{160}\mathrm{Gd}+{}^{186}\mathrm{W}$ collisions is investigated in the framework of quantal transport description, based on the stochastic mean-field (SMF) theory. The SMF theory provides a microscopic approach for nuclear dynamics beyond the time-dependent Hartree-Fock approach by including mean-field fluctuations. Cross sections for the primary fragment production are determined in the quantal transport description and compared with the available data.

The mechanism of direct knockout of a nucleon from heavy deformed nuclei with $A\gtrsim 100$ by photons in the $E_{\gamma }\lesssim 40$ MeV energy range is considered, and the interaction of the ejected nucleon with the rotational degrees of freedom of the final nucleus is taken into account. It is assumed that the rotation frequency of the nucleus is much less than the frequency of its surface vibrations and the Siegert's theorem is in effect. This model was applied to calculation of the total and differential cross sections of direct proton knockout reactions on ${}^{108}\mathrm{Pd}, {}^{160}\mathrm{Gd}$, and ${}^{184,186}\mathrm{W}$ and the bremsstrahlung-induced yield of photoprotons on ${}^{180}\mathrm{Hf}$. Comparison with the experimental data and with the results of a statistical model calculation indicates importance of the direct photoeffect for such nuclei in the considered energy range. Calculations show that for deformed nuclei the interaction of the ejected nucleon with the rotational excitations of the final nucleus results in a significant enhancement of the direct photoeffect cross section. Angular distribution of ejected protons reveals a large asymmetry in the forward direction at $E_{\gamma }>20$ MeV.

Owing to large pressure gradients at early times, standard hydrodynamic model simulations of relativistic heavy-ion collisions do not become reliable until $O\left(1\right)$ $\mathrm{fm}/c$ after the collision. To address this one often introduces a prehydrodynamic stage that models the early evolution microscopically, typically as a conformal, weakly interacting gas. In such an approach the transition from the prehydrodynamic to the hydrodynamic stage is discontinuous, introducing considerable theoretical model ambiguity. Alternatively, fluids with large anisotropic pressure gradients can be handled macroscopically using the recently developed viscous anisotropic hydrodynamics (VAH). In high-energy heavy-ion collisions VAH is applicable already at very early times, and at later times transitions smoothly into conventional second-order viscous hydrodynamics. We present a Bayesian calibration of the VAH model with experimental data for Pb-Pb collisions at the LHC at $\sqrt{s_{NN}}=2.76 \mathrm{TeV}$. We find that the VAH model has the unique capability of constraining the specific viscosities of the quark-gluon plasma at higher temperatures than other previously used models.

Significant advancement in Bayesian inference of nuclear equation of state (EOS) from gravitational wave and x-ray observations of neutron stars (NSs) has been made by the nuclear astrophysics community especially since GW170817. By extending the traditional Bayesian analysis which normally ends at presenting the marginalized posterior probability distribution functions (PDFs) of individual EOS parameters and their correlations (or sometimes only the Pearson correlation coefficients which are only reliably useful when the variables are linearly correlated while they are actually often not), we search for a data-driven and robust empirical formula for the radius $R_{1.4}$ of canonical NSs in terms of the characteristic EOS parameters (features). We also identify the single most important but currently poorly known EOS parameter for determining the $R_{1.4}$. Using three regression-model-building methodologies: bidirectional stepwise feature selection, least absolute shrinkage selection operator (LASSO) regression, and neural network regression on a large set of posterior EOSs and the corresponding $R_{1.4}$ values inferred from earlier comprehensive Bayesian analyses of NS observational data, we systematically and rigorously develop the most probable $R_{1.4}$ formulas with varying statistical accuracy and technical complexity. The most important EOS parameters for determining $R_{1.4}$ are found consistently in each of the feature selection processes to be (in order of decreasing importance): curvature $K_{\mathrm{sym}}$, slope $L$, skewness $J_{\mathrm{sym}}$ of nuclear symmetry energy, skewness $J_0$, incompressibility $K_0$ of symmetric nuclear matter, and the magnitude $E_{\mathrm{sym}}\left({\rho }_0\right)$ of symmetry energy at the saturation density ${\rho }_0$ of nuclear matter.

Background: Spectroscopy of the exotic, neutron unbound beryllium isotope ${}^{13}\mathrm{Be}$ is still a puzzle despite significant experimental efforts.

Purpose: We aim to observe $T=5/2$ states in ${}^{13}\mathrm{B}$, establish spin-parities and spectroscopic factors, and use isospin symmetry to inform spectroscopy of ${}^{13}\mathrm{Be}$.

Methods: Excitation functions for resonance elastic scattering of ${}^{12}\mathrm{Be}$ on protons were measured in the center-of-mass energy range from 1 to 5 MeV.

Results: Two $T=5/2$ states in ${}^{13}\mathrm{B}$ at excitation energies 18.25 and 19.95 MeV were observed. Unambiguous $1/2^{+}$ and $5/2^{+}$ spin-parity assignments were made, and spectroscopic factors were established using the $R$-matrix analysis of the measured ${}^{12}\mathrm{Be}+p$ excitation functions.

Conclusions: We provide the first direct and unambiguous spin-parity assignments and spectroscopic factor measurements for the resonances in the $A=13, T=5/2$ isobaric multiplet. This puts us on a solid footing to identify the 2.3 MeV state in ${}^{13}\mathrm{Be}$ as $5/2^{+}$ and infer the existence of an $s$-wave ($1/2^{+}$) resonance at around 0.6 MeV with relatively small spectroscopic factor.

A coupled-channel nucleon-antinucleon interaction model is developed as an alternative to traditional optical models and is adjusted to reproduce the same $N\overline{N}$ low-energy dataset as the Kohno-Weise potential. The scattering lengths of the antiproton-deuteron system and the level shifts of its lowest hydrogenic states are computed by solving the Faddeev-Merkuriev equations in configuration space. The calculations are carried out with two different nucleon-nucleon interactions and the results compared with those obtained with an optical model to explore the model-dependence, which is found to be weak. The antiproton annihilation densities on deuteron are finally calculated and compared.

While empirical shell model calculations have successfully described low-lying nuclear data for decades, only recently has significant effort been made to quantify the uncertainty in such calculations. Here, we quantify the statistical error in effective parameters for transition operators in empirical calculations in the $sd$ ($1s_{1/2}\text{−}0d_{3/2}\text{−}0d_{5/2}$) valence space, specifically the quenching of Gamow-Teller transitions, effective charges for electric quadrupole ($E2$) transitions, and the effective orbital and spin couplings for magnetic dipole ($M1$) transitions and moments. We find the quenching factor for Gamow-Teller transitions relative to free-space values is tightly constrained. For effective $M1$ couplings, we found isoscalar components more constrained than isovector. This detailed quantification of uncertainties, while highly empirical, nonetheless is an important step towards interpretation of experiments.

Electron capture (EC) decay of a ${}^7\mathrm{Be}$ atom, the rate of which is affected by the electron density at the ${}^7\mathrm{Be}$ nucleus, forms a ${}^7\mathrm{Li}$ atom and emits a neutrino. Herein, we studied the EC decay rate of ${}^7\mathrm{Be}@{\mathrm{C}}_{2n}$ $(2n=24, 28, 32, 36, 50)$, in which those fullerenes have enhanced stability relative to their near neighbors, by using ab initio calculations. The stable and metastable ${}^7\mathrm{Be}$ atom sites and electron density at the ${}^7\mathrm{Be}$ nucleus in ${}^7\mathrm{Be}@{\mathrm{C}}_{2n}$ were calculated. Unlike ${}^7\mathrm{Be}@{\mathrm{C}}_{60}$, the ${}^7\mathrm{Be}$ nucleus sites in ${}^7\mathrm{Be}@{\mathrm{C}}_{2n}$ $(2n=24, 28, 32, 36, 50)$ are always off center and close to the fullerene cage. Due to the bonding interaction between ${}^7\mathrm{Be}$ and the fullerene cage, the electron density at the ${}^7\mathrm{Be}$ nucleus in ${}^7\mathrm{Be}@{\mathrm{C}}_{2n}$ is smaller than those of a single ${}^7\mathrm{Be}$ atom and of ${}^7\mathrm{Be}$ in ${}^7\mathrm{Be}@{\mathrm{C}}_{60}$, leading to the result that the half-life of ${}^7\mathrm{Be}$ in ${}^7\mathrm{Be}@{\mathrm{C}}_{2n}$ increases. Based on equilibrium statistical thermodynamic calculations, the temperature effect on the half-life of ${}^7\mathrm{Be}$ has been analyzed. In contrast to ${}^7\mathrm{Be}@{\mathrm{C}}_{60}$, the temperature only slightly influences the half-life of ${}^7\mathrm{Be}$ in ${}^7\mathrm{Be}@{\mathrm{C}}_{2n}$ suggesting that the EC decay rate of ${}^7\mathrm{Be}$ could be precisely modified by using small fullerene cages.

We analyze the experimental data on nuclei and hypernuclei yields recently obtained by the STAR collaboration. The hybrid dynamical and statistical approaches which have been developed previously are able to describe the experimental data reasonably. We discuss the intriguing difference between the yields of normal nuclei and hypernuclei which may be related to the properties of hypermatter at subnuclear densities. New (hyper)nuclei could be detected via particle correlations. Such measurements are important to pin down the production mechanism.

Contrary to descriptions from coupled-channels or other model calculations, heavy-ion fusion excitation functions are not smooth near and above the Coulomb barrier. There appear to be weak but noticeable oscillations or structures within the excitation functions that can be observed clearly in representation $d\left(\sigma E\right)/dE$ and in the comparison with theoretical calculations $\sigma \left(E\right)-{\sigma }_{\mathrm{th}}\left(E\right)$. A rather similar phenomenon has been studied before and can be explained in light symmetric systems as the influence of the centrifugal barrier penetration only on even angular momentum, but it cannot be extended to heavier, more asymmetric fusion systems. A more thorough investigation may be required to investigate this newly indicated behavior.

An unexpected overlapping behavior has been observed for fusion excitation functions $\sigma \left(E\right)$ from different entrance channels that fuse to the same compound nucleus in energies above the barrier. The overlap appears when the center of mass energy of each excitation function is multiplied by a constant scaling factor. The scaling factors are determined by adjusting and are nearby the ratios of corresponding Coulomb barriers of each entrance channel. Moreover, the corresponding $d\left(\sigma E\right)/dE$ spectra also overlap well in this energy range, including their fine structures. The reasoning behind these behaviors are unknown. One possibility is the compound-channel effect, since the overlap behavior does not occur between collision systems leading to different compound nuclei.

Background: The Hartree-Fock mean-field approximation is standard in combination with energy density functionals (EDF) that account for some dynamical correlations. Breaking and restoring the symmetries of the system allow for the inclusion of additional static correlations. However, exact solutions to evaluate the effectiveness of these methods are rare.

Purpose: To benchmark the Hartree-Fock method with broken and restored rotational symmetry in a system of identical interacting fermions on a one-dimensional quantum ring using model interactions.

Method: The ground-state wave function is found using the Hartree-Fock method both with rotational invariance and with the symmetry broken at the mean-field level. Rotational symmetry is then restored with an angular momentum projection method. The ground-state energies are compared to variational Monte Carlo predictions. This is done for a range of different interactions between the particles.

Results: Breaking the rotational symmetry in the Hartree-Fock mean-field brings little improvement to the ground-state energy in weakly repulsive systems or attractive systems confined on small rings. Larger improvements are found in strongly repulsive systems and attractive systems on larger rings in which the particles form a self-bound system. Symmetry restoration brought only small improvements in most cases but was able to account for most of the remaining correlation energy (after symmetry breaking) in repulsive systems.

Conclusions: The effectiveness of incorporating correlations through rotational symmetry breaking followed by angular momentum projection is demonstrated for one-dimensional quantum rings using model interactions, encouraging generalisations to other symmetries, extensions to higher dimensions, as well as applications in the EDF framework.

Quadrupole collectivity of the lowest-lying states, focusing on $E_x\left(2_1^{+}\right)$ and $B(E2;0_1^{+}\to 2_1^{+})$, have been investigated for the $N=50–82$ Sn nuclei by applying the self-consistent approaches with the semi-realistic interaction M3Y-P6. Both $E_x\left(2_1^{+}\right)$ and $B(E2;0_1^{+}\to 2_1^{+})$ are well reproduced by the spherical Hartree-Fock-Bogoliubov (HFB) plus quasiparticle random-phase approximation (QRPA) calculations in $N\ge 64$, without adjustable parameters. The measured $B\left(E2\right)$ values in the neutron-deficient Sn nuclei cast a puzzle. In $54\le N\le 62$, the spherical $\mathrm{HFB}+\mathrm{QRPA}$ calculations give too strong $B\left(E2\right)$, opposite to the shell-model predictions within the one major shell. Via the constrained-HFB (CHFB) calculations, it is found that the neutron-deficient Sn nuclei are soft against the quadrupole deformation, accounting for the limited applicability of the $\mathrm{HFB}+\mathrm{QRPA}$ approach and possibly giving rise to shape fluctuation. In particular, the potential energy curves (PECs) are almost flat in the range of $|q_0|\lesssim 200{\mathrm{fm}}^2$ in ${}^{106–110}\mathrm{Sn}$. We confirm that the near degeneracy of $n0g_{7/2}$ and $n1d_{5/2}$ triggers weak quadrupole deformation and its balance with the pairing makes PECs flat, which is qualitatively consistent with a recent shell model result in an extended model space, by the calculations shifting the single-particle energy spacing and the pairing strength. These conclusions are supported by the proton-to-neutron ratios of the transition matrix elements and the reference values of $B\left(E2\right)$ with the angular-momentum projection on top of the CHFB solutions.

We study entanglement entropies between the single-particle states of the hole space and its complement in nuclear systems. Analytical results based on the coupled-cluster method show that entanglement entropies are proportional to the particle number fluctuation and the depletion number of the hole space for sufficiently weak interactions. General arguments also suggest that the entanglement entropy in nuclear systems fulfills a volume instead of an area law. We test and confirm these results by computing entanglement entropies of the pairing model and neutron matter, and the depletion number of finite nuclei.

The GlueX experiment at Jefferson Lab studies photoproduction of mesons using linearly polarized $8.5\text{GeV}$ photons impinging on a hydrogen target which is contained within a detector with near-complete coverage for charged and neutral particles. We present measurements of spin-density matrix elements for the photoproduction of the vector meson $\rho$(770). The statistical precision achieved exceeds that of previous experiments for polarized photoproduction in this energy range by orders of magnitude. We confirm a high degree of $s$-channel helicity conservation at small squared four-momentum transfer $t$ and are able to extract the $t$ dependence of natural- and unnatural-parity exchange contributions to the production process in detail. We confirm the dominance of natural-parity exchange over the full $t$ range. We also find that helicity amplitudes in which the helicity of the incident photon and the photoproduced $\rho \left(770\right)$ differ by two units are negligible for $-t<0.5{\text{GeV}}^2/c^2$.

The properties of finite nuclei, bulk nuclear matter, and neutron stars are studied using the relativistic mean field model which includes nonlinear couplings between isoscalar and isovector mesons. The quartic interaction ${\sigma }^2{\delta }^2$ due to isoscalar and isovector scalar, $\sigma$ and $\delta$ mesons, is also taken into account in addition to vector meson mixing ${\omega }^2{\rho }^2$. Several HPNL sets (named from Himachal Pradesh University Nuclear Laboratory) are generated to assess the influence of isoscalar and isovector scalar meson mixed interactions ${\sigma }^2{\delta }^2$ on the density dependence of symmetry energy and neutron star properties. These parametrizations correspond to different values of coupling constant, ${\mathrm{\Lambda }}_{\sigma \delta }$ of $\sigma -\delta$ meson mixing and are obtained by fitting the available experimental data of ground state properties (binding energies and charge radii) for finite nuclei, infinite nuclear matter, and observed maximum mass of PSR $\text{J}0740+6620$ by following the ${\chi }^2$ minimization procedure. Furthermore, the $\sigma -\delta$ mixing is found to have a large influence on the radius and tidal deformability of a canonical neutron star. These new relativistic interactions are found to be simultaneously compatible with the constraints on the equation of state of symmetric nuclear and pure neutron matter from particle flow data in heavy ion collisions, the neutron skin thickness of ${}^{208}\mathrm{Pb}$ from PREX-II results, the mass-radius relations measured from NICER, and the limits of dimensionless tidal deformability of a canonical neutron star from binary neutron star merger GW170817 and GW190814 events.

Reaction-plane deblurring is applied to the triple-differential distributions of protons, deuterons, and negatively charged pions from central Ar $+$ KCl collisions at $1.8\mathrm{GeV}/\mathrm{nucleon}$, measured with the LBL-GSI Streamer Chamber, to yield distributions relative to the true reaction plane of the collisions. Within the reaction plane and in the forward center of mass rapidity region a side ridge away from the beam axis is observed: the distributions peak away from the beam direction for protons and deuterons but not for pions. These findings are consistent with a source of particles moving at an in-plane transverse velocity of $\approx 0.1c$. Transport pawel's BUU calculations yield results in semiquantitative agreement with those from the data.

We present a Bayesian analysis of renormalization-group invariant nucleon-nucleon interactions at leading order in chiral effective field theory ($\chi \mathrm{EFT}$) with momentum cutoffs in the range 400–4000 MeV. We use history matching to identify relevant regions in the parameter space of low-energy constants (LECs) and subsequently infer the posterior probability density of their values using Markov chain Monte Carlo. All posteriors are conditioned on experimental data for neutron-proton scattering observables and we estimate the $\chi \mathrm{EFT}$ truncation error in an uncorrelated limit. We do not detect any significant cutoff dependence in the posterior predictive distributions for two-nucleon observables. For all cutoff values we find a multimodal LEC posterior with an insignificant mode harboring a bound ${}^{1}S_0$ state. The ${}^{3}P_0$ and ${}^{3}P_2$ phase shifts emerging from the Bayesian analysis are less constrained and typically more repulsive compared to the results of a phase shift optimization. We expect that our inference will impact predictions for nuclei. This work demonstrates how to perform inference in the presence of limit-cycle-like behavior and spurious bound states, and lays the foundation for a Bayesian analysis of renormalization-group invariant $\chi \mathrm{EFT}$ interactions beyond leading order.

The possible existence of wobbling modes in the $N=59$ isotones ${}^{95}\mathrm{Kr}, {}^{97}\mathrm{Sr}, {}^{99}\mathrm{Zr}, {}^{101}\mathrm{Mo}, {}^{103}\mathrm{Ru}, {}^{105}\mathrm{Pd}$, and ${}^{107}\mathrm{Cd}$ is explored by the constrained triaxial covariant density functional theory combined with quantum particle rotor model calculations. It is found that there are several states with suitable triaxial deformations and high-$j$ particle configuration to establish wobbling modes in ${}^{97}\mathrm{Sr}, {}^{99}\mathrm{Zr}, {}^{101}\mathrm{Mo}, {}^{103}\mathrm{Ru}$, and ${}^{105}\mathrm{Pd}$. The available experimental energy spectra based on the $\nu {\left(1h_{11/2}\right)}^1$ configuration in ${}^{97}\mathrm{Sr}$ and ${}^{99}\mathrm{Zr}$ are described well. The decreased energy difference between the doublet bands, the enhanced $B{\left(E2\right)}_{\text{out}}/B{\left(E2\right)}_{\text{in}}$ values, as well as the one-phonon oscillation characteristic of the total angular momentum indicate that the two nuclei can be transverse wobbling candidates, which suggests the possibility of a larger region of wobbling modes near the $A\approx 100$ mass region.

Background: The ${}^{10}\mathrm{B}(p,\alpha ){}^7\mathrm{Be}$ reaction is of interest for nuclear reaction theory, nuclear astrophysics, and is important for neutronless (aneutronic) fusion ${}^{11}\mathrm{B}(p,2\alpha ){}^4\mathrm{He}$. At low-energies the $S$ factor of the ${}^{10}\mathrm{B}(p,\alpha ){}^7\mathrm{Be}$ reaction is contributed by the near-threshold resonance $(E_x=8.70\mathrm{MeV};{\frac{5}{2}}^{+})$ with the resonance energy $E=0.01\mathrm{MeV}$ and by higher resonances. Contrary to the $\alpha$ width, the proton resonance width of this resonance is unknown.

Purpose: In this paper, the proton resonance width of the near-threshold resonance is calculated using two different approaches. The values of the proton width are used to calculate the low-energy $S$ factor.

Method: First, the proton resonance width is estimated using the mirror symmetry of the resonance ${}^{11}\mathrm{C}[E_x=8.70\mathrm{MeV};{\frac{5}{2}}^{+}]$ and the mirror bound state ${}^{11}\mathrm{B}[E_x=9.272\mathrm{MeV};{\frac{5}{2}}^{+}]$. In the second approach, this width is estimated using the $R$-matrix definition of the observable resonance width, which is expressed in terms of the $p\text{−}{}^{10}\mathrm{B}$ resonant wave function calculated in the potential approach utilizing the spectroscopic factor.

Results: Depending on the method chosen, the calculated proton resonance width varies from $1.17\times {10}^{-19}\mathrm{MeV}$ to $3.00\times {10}^{-19}\mathrm{MeV}$. The role of the near-threshold resonance is determined using fitting of two low-energy $S$ factors from direct measurement [C. Angulo et al., Z. Phys. A 345, 333 (1993)] and from the indirect Trojan horse method (THM) [A. Cvetinović et al., Phys. Rev. C 97, 065801 (2018)]. Within the framework of the $R$-matrix method using the determined proton resonance widths and the modified THM parameters for six low-lying resonances, the low-energy $S$ factors were calculated and compared with the corresponding experimental $S$ factors. The closest agreement with the data is achieved with the proton resonance widths $1.0\times {10}^{-19}$ MeV when fitting the $S$ factor from the THM indirect measurements, and $1.68\times {10}^{-19}$ MeV and $2.5\times {10}^{-19}$ MeV when fitting the $S$ factor from [Angulo et al., Z. Phys. A 345, 333 (1993)].

Conclusion: Calculated proton resonance widths using the mirror symmetry and the $R$-matrix method are an order of magnitude larger than the phenomenological $S$ factor determined from the $R$-matrix fit of the latest measurements [Van de Kolk et al., Phys. Rev. C 105, 055802 (2022)]. Using the theoretically determined proton resonance widths I achieved excellent fits of the low-energy $S$ factors determined from the direct and indirect measurements.