Bound states of the neutron-deficient, near-dripline nucleus ${}^{36}\mathrm{Ca}$ were populated in two-neutron removal from the ground state of ${}^{38}\mathrm{Ca}$, a direct reaction sensitive to the single-particle configurations and couplings of the removed neutrons in the projectile wave function. Final-state exclusive cross sections for the formation of ${}^{36}\mathrm{Ca}$ and the corresponding longitudinal momentum distributions, both determined through the combination of particle and $\gamma$-ray spectroscopy, are compared to predictions combining eikonal reaction theory and shell-model two-nucleon amplitudes from the USDB, USDC, and ZBM2 effective interactions. The final-state cross-section ratio $\sigma \left(2_1^{+}\right)/\sigma \left(0^{+}\right)$ shows particular sensitivity and is approximately reproduced only with the two-nucleon amplitudes from the ZBM2 effective interaction that includes proton cross-shell excitations into the $pf$ shell. Characterizing the proton $pf$-shell occupancy locally and schematically, an increase of the $sd-pf$ shell gap by 250 keV yields an improved description of this cross-section ratio and simultaneously enables a reproduction of the $B(E2;0_1^{+}\to 2_1^{+})$ excitation strength of ${}^{36}\mathrm{Ca}$. This highlights an important aspect if a new shell-model effective interaction for the region was to be developed on the quest to model the neutron-deficient Ca isotopes and surrounding nuclei whose structure is impacted by proton cross-shell excitations.

The impact of $\beta$-decay rates of an individual nucleus on the $r$-process rare-earth peak abundances has been studied in different astrophysical scenarios. The variation in $\beta$-decay rates by a factor of 10 can produce large abundance uncertainties in the rare-earth mass region, while fission deposition can significantly reduce this uncertainty, which is not a suggested case by the current simulations of neutron-star mergers with moderately neutron-rich conditions where fission is less active. The most impactful nuclei include even-neutron-number ($N$) nuclei on the early $r$-process equilibrium path or $r$-process freeze-out path and nuclei with $N=100$, 102, and 104. It is found that the variations in the $\beta$-decay rate of nuclei located to the left and right sides of the $r$-process freeze-out path have significant different effects on rare-earth peak abundance.

In this paper we analyze the associated production of a vector meson with the bound-free $e^{+}{e}^{-}$ process in ultraperipheral $\mathrm{PbPb}$ collisions through the double scattering mechanism for the energy of the CERN Large Hadron Collider (LHC). Such process is characterized by the presence of a meson and a positron in the final state and by a forward hydrogen-like ion with a distinct electric charge. Predictions for the total cross sections and rapidity distributions considering the rapidity ranges covered by the ALICE, CMS, and LHCb detectors are presented. The high values predicted for the cross sections (and event rates) indicate that an experimental analysis of the $\varphi +e^{+}$ and $J/\mathrm{\Psi }+e^{+}$ final states may become feasible in the future.

A realistic evaluation of the Coulomb potential has been conducted for a few selected nuclei using available model-independent data for the charge density and the recent development of the Coulomb energy-density functional. Employing the Woods-Saxon potential as a nuclear component, we can quantify the differences in proton single-particle energies caused by deviations from the model-independent data of the uniform distribution, the two-parameter Fermi function, and the charge density obtained from a microscopic Hartree-Fock calculation using the effective Skyrme interaction. The obtained energy differences are generally small in magnitude, typically around 100 keV or less, given that the parameters of the charge density models are appropriately determined. However, considerably larger differences arise when the last occupied state is highly filled and, at the same time, has a small orbital angular momentum. A notable example of such nuclei is the sulfur isotopes ($Z=16$). Unfortunately, the uniform distribution cannot be used to evaluate the Coulomb exchange term within a well-established method due to its lack of differentiability at the surface of a nucleus. Traditionally, the missing exchange term is corrected by excluding the contribution of the last proton to the direct term. Our investigation of this approach reveals that its effect simply introduces the factor $(Z-1)/Z$ into the Coulomb direct term. For medium to heavy nuclei (typically beyond the $sd$ shell), the resulting proton levels are 300–800 keV higher than those obtained with the exact Fock term. Conversely, the results for lighter nuclei tend to be the opposite, as the factor $(Z-1)/Z$ decreases rapidly as the atomic number approaches 1. Hence, this traditional approach should be avoided for precise nuclear structure calculations based on Woods-Saxon radial wave functions, particularly for shell-model calculations of the isospin-symmetry breaking correction to $\beta$-decay rates for electroweak interaction studies [J. C. Hardy and I. S. Towner, Phys. Rev. C 102, 045501 (2020), and references therein]. The present study also suggests that the Coulomb exchange term should be included within the Woods-Saxon potential, using the Slater approximation or beyond, along with a realistic model of charge density.

Nuclear fission produces fragments endowed with typically half a dozen units of angular momentum. After scission has occurred, the fragments are still interacting via the Coulomb force which exerts a torque on deformed fragments, thereby accelerating their rotations. The essential features of this effect can be understood by simple perturbative considerations from which the effect on the fragment spin distributions can be obtained. Complete dynamical calculations of the coupled evolution of the spins validate the perturbative treatment, which ignores the second-order terms, showing that the fragment spins evolve essentially independently in the presence of the Coulomb torques.

We performed a search for three-quasiparticle high-$K$ isomer candidates in odd-even Md–Rg nuclei by considering the lowest lying $1\pi 2\nu$ and $3\pi$ excitations. Our approach involves calculating the energies of different nuclear configurations using a microscopic-macroscopic model with the Woods-Saxon potential. We explore three pairing scenarios: blocking, quasiparticle method, and particle number projection formalism. The optimal deformations for both ground states and high-$K$ configurations are determined through a four-dimensional energy minimization process. By analyzing the obtained excitation energies, we discuss the most promising candidates for high-$K$ isomers and compare them, where possible, with existing experimental data. We also discuss a possible isomer $\alpha$-decay hindrance by using calculated $Q_{\alpha }$ hindrances.

A ${}^{13}\mathrm{B}(d,d^{\prime })$ inelastic scattering experiment was carried out using a 23 MeV/nucleon ${}^{13}\mathrm{B}$ beam in order to search for the missing positive parity state with a configuration of ${}^{12}{\mathrm{B}}_{\mathrm{g}.\mathrm{s}.}\otimes d_{5/2}$ in the $N=8$ neutron-rich nucleus ${}^{13}\mathrm{B}$, referred to as the $d$-wave neutron excitation state. Several states at excitation energies of 3.6(1), 4.2(1), 5.4(2), and 6.5(2) MeV in ${}^{13}\mathrm{B}$ were observed in its excitation energy spectra, which were derived from the energies and angles of the scattered deuterons from ${}^{13}\mathrm{B}$ using the missing mass method. To determine the parity of each populated state, the inelastic scattering differential cross sections (DCSs) were compared to the distorted wave Born approximation (DWBA) calculations. The 5.4- and 6.5-MeV states were inferred to be positive parity states and considered as potential candidates for the missing $d$-wave neutron excitation state. The gap between $s$ and $d$ shells in ${}^{13}\mathrm{B}$ and the systematic behavior of neutron-rich Boron isotopes were also investigated based on the experimental findings.

The ${}^{25}\mathrm{Al}(p,\gamma ){}^{26}\mathrm{Si}$ reaction is part of a reaction network with impact on the observed galactic ${}^{26}\mathrm{Al}$ abundance. A new determination of the proton strength of the lowest $\ell =0$ proton resonance in ${}^{26}\mathrm{Si}$ is required to more precisely calculate the thermal reaction rate. To this end, the ${}^{25}\mathrm{Al}(d,n){}^{26}\mathrm{Si}$ proton-transfer reaction is measured in inverse kinematics using an in-flight radioactive beam at the RESOLUT facility. Excitation energies of the lowest ${}^{26}\mathrm{Si}$ proton resonances are measured and cross sections are determined for the lowest $\ell =0$ resonance associated with the $3_3^{+}$ state at 5.92(2) MeV. Coupled reaction channels calculations using fresco are performed to extract the $\ell =0$ spectroscopic factor for the $3_3^{+}$ state. The proton width for the $3_3^{+}$ state in ${}^{26}\mathrm{Si}$ is determined to be ${\mathrm{\Gamma }}_p=2.19\left(45\right)$ eV and the $(p,\gamma )$ resonance strength for the $3_3^{+}$ state is extracted as 0.026(10) eV. This resonance dominates the ${}^{25}\mathrm{Al}(p,\gamma ){}^{26}\mathrm{Si}$ reaction rate above 0.2 GK.

The electric-dipole $\left(E1\right)$ photon strength function (PSF), which is a key input in the statistical model calculations for astrophysical neutron-capture reaction rates, has been studied with a focus on the important energy ranges of the emitting $\gamma$ rays. Comparing the available experimental data of the $E1$ PSF with the strength predicted by microscopic models, we find that the uncertainties in the $E1$ PSF below the neutron separation energy have a great impact on the neutron-capture reaction rates. A further study on the sensitivities of the reaction rate to the variations of the $E1$ PSF at different $\gamma$-ray energies indicates that there is an effective energy window in which the $E1$ PSF contributes greatly to the neutron-capture reaction rates. We propose two functions to describe this window, which can be applied to the nuclei with dominant transitions to the continuum levels and is applicable to the general astrophysical environments of neutron captures. Employing the Gaussian approximation function of the effective window, we can conveniently get several specific effective energy ranges according to the contributions to the astrophysical rate. It is found that currently available experimental data of the $E1$ PSF do not completely cover these important energy ranges. Further theoretical and experimental studies are needed in the proposed energy ranges to improve the descriptions of the $E1$ PSFs.

Excited states in ${}^{57}\mathrm{Mn}$ are populated using the ${}^{55}\mathrm{Mn}({}^{18}\mathrm{O}$, ${}^{16}\mathrm{O}){}^{57}\mathrm{Mn}$ two-neutron transfer reaction at the FN tandem accelerator in Cologne. Lifetimes of excited nuclear states in ${}^{57}\mathrm{Mn}$ were determined utilizing the Doppler-shift attenuation method. A comparison between experiment and shell-model theory was made for excitation energies and reduced transition strengths along the odd-$Z$ isotopes Sc, V, Mn, and Co. The new results on transition strengths in ${}^{57}\mathrm{Mn}$ are described well by the standard interactions GXPF1A and KB3G. The development along the $N=32$ isotones for these odd-$Z$ nuclei and discrepancies between experiment and theory are discussed.

Background: Multinucleon transfer (MNT) reactions involving heavy projectile and target combinations stand as a promising method for synthesizing new neutron-rich exotic nuclei, which may not be possible using hot or cold fusion reactions or fragmentation. Exploring the mechanisms behind MNT reactions is essential and it requires a comprehensive theoretical framework that can explain the physical observables in these reactions.

Purpose: This work aims to show that the quantal diffusion approach based on the stochastic mean-field (SMF) theory is capable of explaining the reaction dynamics observed in MNT reactions. Primary product mass distributions in ${}^{48}\mathrm{Ca}+{}^{244}\mathrm{Pu}$ reaction at $E_{\text{c.m.}}=203.2\mathrm{MeV}$ and ${}^{86}\mathrm{Kr}+{}^{198}\mathrm{Pt}$ reaction at $E_{\text{c.m.}}=324.2\mathrm{MeV}$ are calculated and compared with the available experimental data.

Methods: In this work, we utilize the time-dependent Hartree-Fock (TDHF) calculations to analyze the mean-field reaction dynamics computationally in the reactions ${}^{48}\mathrm{Ca}+{}^{244}\mathrm{Pu}$ and ${}^{86}\mathrm{Kr}+{}^{198}\mathrm{Pt}$ for a broad range of initial angular momenta. Quantal transport description based on the SMF approach is used to calculate quantal diffusion coefficients and mass variances in ${}^{48}\mathrm{Ca}+{}^{244}\mathrm{Pu}$ and ${}^{86}\mathrm{Kr}+{}^{198}\mathrm{Pt}$ systems. The primary products arising from quasifission reactions are described by joint probability distribution in the SMF approach and those arising from fusion-fission are estimated by using the statistical deexcitation code gemini$++$.

Results: Mean values of charge and mass numbers, scattering angles of the primary reaction products, and the total kinetic energies after the collision are calculated within the TDHF framework for a broad range of initial angular momenta. Throughout all the collisions, drift toward the mass symmetry and large mass dispersion associated with this drift are observed. The calculated primary fragment and mass distributions using the SMF approach successfully explain experimental observations for the ${}^{48}\mathrm{Ca}+{}^{244}\mathrm{Pu}$ and ${}^{86}\mathrm{Kr}+{}^{198}\mathrm{Pt}$ systems.

Conclusions: The primary mass distributions, mean values of binary products, and mass dispersions are determined and results are compared with the available experimental data. The observed agreement between the experimental data and SMF results highlights the effectiveness of the quantal diffusion mechanism based on the SMF approach, which does not include any adjustable parameters other than standard parameters of Skyrme energy density functional.

The repulsive three-body force between the lambda ($\mathrm{\Lambda }$) hyperon and medium nucleons is a key element in solving the hyperon puzzle in neutron stars. We investigate the binding energies of the $\mathrm{\Lambda }$ hyperon in hypernuclei to verify the repulsive $\mathrm{\Lambda }$ potentials from the chiral effective field theory ($\chi \mathrm{EFT}$) employing the Skyrme Hartree-Fock method. We find that the $\chi \mathrm{EFT}\mathrm{\Lambda }$ potential with $\mathrm{\Lambda }NN$ three-body forces reproduces the existing hypernuclear binding energy data, whereas the $\mathrm{\Lambda }$ binding energies are overestimated without the $\mathrm{\Lambda }NN$ three-body force. Additionally, we search for the parameter space of the $\mathrm{\Lambda }$ potentials by varying the Taylor coefficients of the $\mathrm{\Lambda }$ potential and the effective mass of $\mathrm{\Lambda }$ at the saturation density. Our analysis demonstrates that the parameter region consistent with the $\mathrm{\Lambda }$ binding energy data spans a wide range of the parameter space, including even more repulsive potentials than the $\chi \mathrm{EFT}$ prediction. We confirm that these strong repulsive $\mathrm{\Lambda }$ potentials suppress the presence of $\mathrm{\Lambda }$ in neutron star matter. We found that the $\mathrm{\Lambda }$ potentials repulsive at high densities are favored when the depth of the $\mathrm{\Lambda }$ potential at the saturation density, $U_{\mathrm{\Lambda }}\left({\rho }_0\right)=J_{\mathrm{\Lambda }}$, is $J_{\mathrm{\Lambda }}\gtrsim -29\text{MeV}$, while attractive ones are favored when $J_{\mathrm{\Lambda }}\lesssim -31\text{MeV}$. This suggests that future high-resolution data of hypernuclei could rule out the scenario in which $\mathrm{\Lambda }$'s appear through the precise determination of $J_{\mathrm{\Lambda }}$ within the accuracy of $1\text{MeV}$.

$\beta$-delayed $\gamma$-neutron spectroscopy has been performed on the decay of $A=84$ to 87 gallium isotopes at the RI-beam Factory at the RIKEN Nishina Center using a high-efficiency array of ${}^3\mathrm{He}$ neutron counters (BRIKEN). $\beta \text{−}2n\text{−}\gamma$ events were measured in the decays of all of the four isotopes for the first time, which is direct evidence for populating the excited states of two-neutron daughter nuclei. Detailed decay schemes with the $\gamma$ branching ratios were obtained for these isotopes, and the neutron emission probabilities ($P_{xn}$) were updated from the previous study. Hauser-Feshbach statistical model calculations were performed to understand the experimental branching ratios. We found that the $P_{1n}$ and $P_{2n}$ values are sensitive to the nuclear level densities of $1n$ daughter nuclei and showed that the statistical model reproduced the $P_{2n}/P_{1n}$ ratio better when experimental levels plus shell-model level densities fit by the Gilbert-Cameron formula were used as the level-density input. We also showed the neutron and $\gamma$ branching ratios are sensitive to the ground-state spin of the parent nucleus. Our statistical model analysis suggested $J\le 3$ for the unknown ground-state spin of the odd-odd nucleus ${}^{86}\mathrm{Ga}$, from the $I_{\gamma }(4^{+}\to 2^{+})/I_{\gamma }(2^{+}\to 0^{+})$ ratio of ${}^{84}\mathrm{Ga}$ and the $P_{2n}/P_{1n}$ ratio. These results show the necessity of detailed understanding of the decay scheme, including data from neutron spectroscopy, in addition to $\gamma$ measurements of the multineutron emitters.

Background: The structure and dynamics of many-body systems are the result of a delicate interplay between underlying interactions. Fermionic pairing, for example, plays a central role in various physical systems, ranging from condensed matter to nuclear systems, where it can lead to collective phenomena such as superconductivity and superfluidity. In atomic nuclei, the interplay between pairing and particle-hole interactions leads to a high degree of complexity and intricate entanglement structures. Despite this apparent complexity, symmetries emerge and manifest themselves in observable regular patterns. These symmetries and their breakings have long been used to determine relevant degrees of freedom and simplify classical descriptions of many-body systems.

Purpose: This work explores the potential utility of quantum computers with arrays of qudits in simulating interacting fermionic systems, when the qudits can naturally map the relevant degrees of freedom determined by an underlying symmetry group.

Method: The Agassi model of fermions interacting via particle-hole and pairing interactions is based on an underlying $\mathrm{so}\left(5\right)$ algebra. Such systems can intuitively be partitioned into pairs of modes with five basis states, which thus naturally map to arrays of $d=5$ qudits (qu5its). Classical noiseless simulations of the time evolution of systems with up to twelve qu5its are performed, by implementing quantum circuits that are developed herein, using python codes invoking Google's cirq software. The resource requirements of the qu5it circuits are analyzed and compared with two different mappings to qubit systems: a physics-aware Jordan-Wigner mapping requiring four qubits per mode pair and a state-to-state mapping requiring three qubits per mode pair.

Results: While the dimensionality of Hilbert spaces in mappings to qu5it systems are less than those for the corresponding qubit systems, the number of entangling operations, depending on the available hardware, can either be greater or smaller than for the physics-aware Jordan-Wigner mapping. The state-to-state mapping, while having a smaller Hilbert space than Jordan-Wigner mappings, appears to be the least efficient in gate counts. Further, a previously unknown sign problem has been identified from Trotterization errors in time evolving high-energy excitations.

Conclusions: There appear to be advantages in employing quantum computers with arrays of qudits to perform simulations of many-body dynamics that exploit the role of underlying symmetries, specifically in lowering the required quantum resources and in reducing anticipated errors that take the simulation out of the physical space. If the necessary entangling gates are not directly supported by the hardware, physics-aware mappings to qubits may, however, be advantageous for other aspects.

The longitudinal asymmetry in relativistic heavy ion collisions arises from the fluctuation in the number of nucleons involved. This asymmetry causes a rapidity shift in the center of mass of the participating zone. Both the rapidity shift and the longitudinal asymmetry have been found to be significant at the top CERN Large Hadron Collider (LHC) energy for collisions of identical nuclei, and the longitudinal asymmetry is important for reconstructing the colliding vertex and correcting the rapidity shift. However, much discussion of the longitudinal asymmetry has treated the initial condition as a nonzero momentum contributed only by the number of participants, i.e., the asymmetry depends only on the number of participating nucleons. So we naturally raise a physical problem, can other initial conditions, such as two typical initial conditions for nuclei, geometric configuration, and momentum distribution, provide effects on the longitudinal asymmetry? Therefore, in this work we consider other effects on the longitudinal asymmetry other than the fluctuation in the number of participants, e.g., the $\alpha$ clustering structure as well as the intrinsic momentum distribution in the target and projectile nuclei for the collisions in the framework of a multiphase transport (AMPT) model. By introducing systems with different $\alpha$-clustering structure and intrinsic momentum distribution, we calculated the ratio of the rapidity distributions of different systems and extracted expansion coefficients to analyze the difference contributed by these factors. We also investigated the possible effect of the non-Gaussian distribution on the rapidity distribution. These results can help us to constrain the initial conditions and reconstruct the colliding vertex in ultrarelativistic heavy ion collisions, and suggest a quantitative correction on the final state measurement and a possible correlation between the initial condition and the final state observable in LHC and BNL Relativistic Heavy Ion Collider energy.

The relation between the nuclear European Muon Collaboration (EMC) effect and the nucleon-nucleon short-range correlation is a hot topic in high-energy nuclear physics, ever since a peculiar linear correlation between these two phenomena was discovered. In this paper, the contribution to the nuclear EMC effect arising from the short-range correlated nucleons is examined in a nucleon-swelling model. We find that the structure modifications of the nucleon-nucleon short-range correlation (SRC) nucleons reproduce more or less the measured EMC ratios of light nuclei, while they are not enough to explain the measured EMC ratios of heavy nuclei. We speculate that the hypothesis of a causal connection between SRC and the EMC effect is not exact, or the universality of the inner structure of the SRC nucleon is violated noticeably from light to heavy nuclei, or there are other origins for the EMC effect.

In the noisy intermediate-scale quantum era, variational algorithms have become a standard approach to solving quantum many-body problems. Here, we present variational quantum eigensolver results of selected oxygen isotopes within the shell-model description. The aim of the present work is to locate the neutron drip line of the oxygen chain using unitary coupled cluster type Ansätze with different microscopic interactions (DJ16, JISP16, and N3LO), in addition to a phenomenological USDB interaction. While initially infeasible to execute on contemporary quantum hardware, the size of the problem is reduced significantly using qubit tapering techniques in conjunction with custom circuit design and optimization. The optimal values of Ansatz parameters from classical simulation are taken for the DJ16 interaction, and the tapered circuits are run on IonQ's Aria, a trapped-ion quantum computer. After applying gate error mitigation for three isotopes, we reproduced exact ground-state energies within a few percent error. The postprocessed results from hardware also clearly show ${}^{24}\mathrm{O}$ as the drip line nucleus of the oxygen chain. Future improvements in quantum hardware could make it possible to locate drip lines of heavier nuclei.

Based on the Boltzmann-Uehling-Uhlenbeck (BUU) transport equation, a medium correction to the elastic nucleon-nucleon ($NN$) cross sections is given by comparing the width of the isovector giant dipole resonance in ${}^{208}\mathrm{Pb}$ and the nuclear stopping obtained from the BUU equation with those from experimental measurements. For the nuclear stopping, we choose the scaled rapidity distributions and the nuclear stopping power $vartl$, denoted as the ratio of the variances of the transverse to that of the longitudinal rapidity distributions, of central ${}^{197}\mathrm{Au}+{}^{197}\mathrm{Au}$ collisions at the energy of $150A\mathrm{MeV}$ measured by the INDRA and the FOPI collaborations. This enables us to provide a unified medium correction of elastic $NN$ cross sections for distinct energy regimes. A reliable in-medium $NN$ cross section, as given here, will reduce the uncertainties of the BUU equation when applying it to nuclear collective motion and heavy-ion collisions to extract the information of the nuclear equation of state.

It is known that multiple partonic scatterings in high-energy proton-proton ($pp$) collisions must happen in parallel. However, a rigorous parallel scattering formalism, taking energy sharing properly into account, fails to reproduce factorization, which on the other hand is the basis of almost all $pp$ event generators. In addition, binary scaling in nuclear scatterings is badly violated. These problems are usually “solved” by simply not considering strictly parallel scatterings, which is not a solution. I will report on new ideas (leading to EPOS4), which allow recovering perfectly factorization, and also binary scaling in $AA$ collisions, in a rigorous unbiased parallel scattering formalism. In this new approach, dynamical saturation scales play a crucial role, and this seems to be the missing piece needed to reconcile parallel scattering with factorization. From a practical point of view, one can compute within the EPOS4 framework parton distribution functions (EPOS PDFs) and use them to compute inclusive $pp$ cross sections. So, for the first time, one may compute inclusive jet production (for heavy or light flavors) at very high transverse momentum ($p_t$) and at the same time in the same formalism study flow effects at low $p_t$ in high-multiplicity $pp$ events, making EPOS4 a full-scale “general purpose event generator”. I discuss applications, essentially multiplicity dependencies (of particle ratios, mean $p_t$, charm production) which are very strongly affected by the saturation issues discussed in this paper.