The spin structure functions of the proton and the deuteron were measured during the EG4 experiment at Jefferson Lab in 2006. Data were collected for longitudinally polarized electron scattering off longitudinally polarized ${\mathrm{NH}}_3$ and ${\mathrm{ND}}_3$ targets, for $Q^2$ values as small as 0.012 and 0.02 ${\mathrm{GeV}}^2$, respectively, using the CEBAF Large Acceptance Spectrometer. This is the archival paper of the EG4 experiment that summarizes the previously reported results of the polarized structure functions $g_1$, $A_1{F}_1$, and their moments ${\overline{\mathrm{\Gamma }}}_1$, ${\overline{\gamma }}_0$, and ${\overline{I}}_{\mathrm{TT}}$, for both the proton and the deuteron. In addition, we report on new results on the neutron $g_1$ extracted by combining proton and deuteron data and correcting for Fermi smearing, and on the neutron moments ${\overline{\mathrm{\Gamma }}}_1$, ${\overline{\gamma }}_0$, and ${\overline{I}}_{\mathrm{TT}}$ formed directly from those of the proton and the deuteron. Our data are in good agreement with the Gerasimov-Drell-Hearn sum rule for the proton, deuteron, and neutron. Furthermore, the isovector combination was formed for $g_1$ and the Bjorken integral ${\overline{\mathrm{\Gamma }}}_1^{p-n}$, and it was compared to available theoretical predictions. All of our results, to the best of our knowledge, provide for the first time extensive tests of spin observable predictions from chiral effective field theory $\left(\chi \mathrm{EFT}\right)$ in a $Q^2$ range commensurate with the pion mass. They motivate further improvement in $\chi \mathrm{EFT}$ calculations from other approaches such as the lattice gauge method.

Lifetimes of low-lying excited states in ${}^{102}\mathrm{Mo}$ populated in the two-neutron transfer reaction ${}^{100}\mathrm{Mo}({}^{18}\mathrm{O},{}^{16}\mathrm{O}){}^{102}\mathrm{Mo}$ were measured using the recoil distance Doppler shift method at the IFIN-HH Tandem accelerator. Lifetimes of the $2_1^{+}, 0_2^{+}, 4_1^{+}, 2_2^{+}, 2_3^{+}, 3_1^{+}, 6_1^{+}$, ($0_3^{+}$), $4_2^{+}$, ($3_1^{-}$), and ($5_1^{-}$) states were obtained. The deduced electromagnetic transition strengths have been compared to calculations performed in the interacting boson model framework including models representing the U(5) and X(5) symmetries. It is found that ${}^{102}\mathrm{Mo}$ lies between the U(5) limit and the X(5) critical point symmetry.

High-spin spectroscopic study of ${}^{202}\mathrm{Po}$ $(Z=84,N=118)$ has been carried out using the ${}^{195}\mathrm{Pt}({}^{12}\mathrm{C},5\mathrm{n}){}^{202}\mathrm{Po}$ fusion-evaporation reaction. An extended level scheme has been proposed up to an excitation energy of $E_x\approx 8$ MeV and angular momentum of $27\hslash$, with the addition of 57 newly observed $\gamma$-ray transitions, along with the revisions in the placement of eight already known transitions and the multipolarities of four of these transitions. The energy of the unobserved $8^{+}\to 6^{+}$ transition has been proposed to be 9.0(5) keV, which resolves the uncertainty in the excitation energy of the levels above the $6^{+}$ state. Three new sequences of $M1$ transitions have also been identified in the high excitation energy regime and included in the proposed level scheme. The large-scale shell-model calculations for $Z>82$ and $N<126$ valence space have been carried out using PBPOP interaction, which explained the overall level scheme for both the positive and negative parity states. The calculations successfully reproduced the purity of the proton $\pi h_{9/2}$ dominated $8^{+}$ isomeric state, and also explained the missing $E2$ decay of the ${12}^{+}$ isomeric state in terms of changing nucleonic configurations.

Coulomb-catalyzed deuteron-induced fission reactions of low deuteron energy in dense plasmas are discussed. Cross section of ${}^{238}\mathrm{U}$-catalyzed deuteron-induced ${}^{235}\mathrm{U}$-fission reactions is deduced with the aid of the measured cross section of the usual neutron-induced fission of ${}^{236}\mathrm{Np}$ and using standard perturbation theory of quantum mechanics. The obtained cross section, which is expected to be vanishing according to recent knowledge, has finite value. An experimental proposal for the observation of the process is sketched, too, that may have also importance from the point of view of low-energy nuclear reactions.

Background: Fission modes are typically characterized by fragment mass and total kinetic energy centroids, around which a distribution of these variables is observed. These distributions are usually fitted with Gaussian functions.

Purpose: To investigate how the properties of these “Gaussian fission modes” compare with underlying “theoretical fission modes” defined from the potential energy surface of the fissioning nuclei.

Methods: A simple approach, inspired by the scission point model, is introduced to investigate the impact of anharmonicity of the potential along the scission line on Gaussian mode properties. This approach is also used to evaluate an “effective potential” from the yields.

Results: Several Gaussian functions are usually required to fit yields from nonharmonic potentials associated with a unique theoretical mode. “Effective fission modes”, defined from the wells of the effective potentials, can be very different to the Gaussian modes. For instance, the S1 and S2 Brosa modes contribute to the same effective potential well at scission.

Conclusions: Although Gaussian fits have proven useful to identify the role of shell effects in fission, they are not always associated with fission modes originating from valleys in the potential energy surfaces. Instead, properties of fission modes are better investigated with effective potentials extracted from the yields, preferably with a broad range of excitation energies.

This paper presents a theoretical study on the production of leptons from decay of heavy-flavor hadrons (denoted as HFLs) in high-energy nuclear collisions at the CERN Large Hadron Collider. The $\mathit{pp}$ baseline is calculated by the fonll program, which matches the next-to-leading order perturbative QCD (pQCD) calculation with the next-to-leading-logarithm large-$p_T$ resummation. The in-medium propagation of heavy quarks is driven by the modified Langevin equations, which consider both the elastic and inelastic partonic interactions. We propose a method to separate the respective influence of the six factors, i.e., $\mathit{pp}$ spectra, cold nuclear matter (CNM) effects, in-medium energy loss (E-loss), fragmentation functions (FFs), coalescence (Coal), and decay channels, which may contribute to the larger $R_{AA}$ of HFL $\leftarrow b$ compared to that of HFL $\leftarrow c$ in nucleus-nucleus collisions. Based on quantitative analysis, we demonstrate that both coalescence hadronization decay channels and the mass-dependent E-loss play an essential role at $p_T<5\mathrm{GeV}$, while the latter dominates the higher $p_T$ region. It is also found that the influences of the CNM effects and FFs are insignificant. At the same time, different initial $\mathit{pp}$ spectra of charm and bottom quarks have a considerable impact at $p_T>5\mathrm{GeV}$. Furthermore, we explore the path-length dependence of jet quenching by comparing the HFL $R_{AA}$ in two different collision systems. Our investigations show smaller HFL $R_{AA}$ in $\mathrm{Pb}+\mathrm{Pb}$ than in $\mathrm{Xe}+\mathrm{Xe}$ within the same centrality bin, consistent with the ALICE data. The longer propagation time and more effective energy loss of heavy quarks in $\mathrm{Pb}+\mathrm{Pb}$ collisions play critical roles in the stronger yield suppression of the HFLs compared to that in $\mathrm{Xe}+\mathrm{Xe}$. In addition, we observe a scaling behavior of the HFL $R_{AA}$ in $\mathrm{Xe}+\mathrm{Xe}$ and $\mathrm{Pb}+\mathrm{Pb}$ collisions.

I present a new approximation of the $S$-matrix dependence on momentum $q$, formulated as a sum of a rational function and a truncated sinc series. This approach enables pointwise determination of the $S$ matrix with specified resolution, capturing essential features such as resonance behavior with high accuracy. The resulting approximation provides a separable kernel for the Marchenko equation (fixed-$l$ inversion), reducing it to a system of linear equations for the expansion coefficients of the output kernel. Numerical results demonstrate good convergence of this method, applicable to both unitary and nonunitary $S$ matrices. Convergence is further validated through comparisons with an exactly solvable square-well potential model. The method is applied to analyze $S_{31}$ $\pi N$ scattering data.

We investigate the importance of the non-coplanar degree of freedom in the fusion dynamics. The total interaction potential ($V_T$) and its associated barrier characteristics (barrier height, $V_B$, and barrier radius, $R_B$) are calculated for both compact and elongated configurations of the colliding nuclei across the range of non-coplanar orientations. This analysis is performed for the projectile-target (P-T) combinations ${}^{32}\mathrm{S}+{}^{150}\mathrm{Sm}$, ${}^{32}\mathrm{S}+{}^{154}\mathrm{Sm}$, and ${}^{18}\mathrm{O}+{}^{194}\mathrm{Pt}$, previously used for coplanar analysis in the literature. We quantify the influence of non-coplanar orientations on the fusion barrier compared to coplanar configurations for both high-barrier non-coplanar orientation (${\varphi }_H$) and low-barrier non-coplanar orientations (${\varphi }_l$). The capture cross sections are calculated using the extended $\ell$-summed Wong model. Our results demonstrate a considerable improvement in the agreement with the experimental capture cross sections when the non-coplanar degree of freedom is incorporated. Additionally, we explore the dependence of capture cross sections on the projectile deformation along with the target deformation within the non-coplanar framework, highlighting the crucial role of non-coplanarity in precisely describing the fusion dynamics.

In a recent article [Phys. Rev. C 108, 034309 (2023)], we proposed a projected shell model method for the calculation of nuclear level density (NLD) in deformed even-even nuclei. The current article presents the subsequent study of NLDs in odd-mass nuclei as well as a comparative analysis between our calculated NLDs in adjacent even-even and odd-$A$ systems. Since one nucleon in the odd-mass system remains blocked from participating in the pair formation, resulting in a weakened pairing (assessed by a smaller BCS pairing gap $\mathrm{\Delta }$), pronounced differences between the NLDs in an odd-mass (both even-odd and odd-even) nucleus and its immediate even-even neighbor have been found. In general, the structure-dominated variations, which were found to be prominent in the even-even NLD at low energies, are greatly suppressed in the odd-mass systems. Specifically, from excitation energy as low as 2 MeV, the calculated densities of odd-parity and even-parity levels in odd-mass nuclei show an equal division signaling faster attainment of the statistical behavior. Nuclear level-spin distributions of both parities have been seen to adopt a regular Gaussian shape earlier than that found in the even-even system. Moreover, the pleasant property of our shell-model results, that each of our calculated levels is an eigenstate of angular momentum, allows us to extract the values of the energy-dependent dispersion $\sigma$ of Ericson's spin-distribution formula and plot $\rho (E,I,\pi )$, the energy-, spin-, and parity-dependent level density.

In this work, we present a new approximate method for obtaining simple wave functions for the ground state of exotic nuclei with a neutron halo. We model the system as a two-cluster structure, treating the core and halo as inert objects. The relative wave function is expressed as a combination of simple harmonic oscillator states, with the oscillator parameter determined from the separation energy. Since these wave functions lack the expected exponential decay, we introduce a simple multiplicative renormalization factor based on the nuclear root-mean-square radius. This approach, combining oscillator wave functions and the renormalization factor, is then applied to calculate dipole strength distributions $dB(E1,\varepsilon )/d\varepsilon$ and Coulomb dissociation cross section $d\sigma (E1,\varepsilon )/d\varepsilon$ for several $1n$- and $2n$-halo nuclei. The results show excellent agreement with the available experimental data.

We calculate, to second order in the scattering length between two fermions, the Landau quasiparticle interaction for a low-density mixture of two fermion species with unequal densities at temperature zero. From the Landau parameters we evaluate the energy density and find agreement with the result of Kanno [Prog. Theor. Phys. 44, 813 (1970)]. The calculations are then extended to the case of two fermion components with different total densities, each with two spin components, a situation of interest in nuclear physics and astrophysics, where the species are neutrons and protons. An interesting finding is that, for low proton concentrations, $x\ll 1$, the leading term in the energy density, beyond the $x^{5/3}$ contribution from the kinetic energy and the $x^2$ one due to the two-body interaction in the mean-field approximation, varies as $x^{7/3}lnx$. This is to be contrasted with the higher powers of $x$ implicit in many phenomenological energy-density functionals employed in nuclear physics, such as those of the Skyrme type.

Background: A negative muon in the $1s$ orbital of a muonic atom can be captured by a nucleus, leading to subsequent nuclear decay processes. The accurate prediction of total nuclear capture rates, which could be crucial in fields such as geochemistry, nuclear astrophysics, and semiconductor device development, remains challenging with current physics models.

Purpose: This study aims to develop a comprehensive machine learning (ML) model to estimate the total nuclear capture rate of a negative muon, integrating physical information and experimental data within a Bayesian framework.

Methods: The study employs an ML model based on Gaussian process regression, using experimental data with evaluated uncertainties as training data. The model incorporates the Goulard-Primakoff formula as prior information and applies a transfer learning approach to improve estimations, particularly in regions where data on isotopically enriched elements are sparse.

Results: The developed ML model is shown to outperform theoretical physics models in both accuracy and comprehensiveness, with key experiments identified to further refine the model performance.

Conclusions: The estimates generated in this study will be incorporated into muon nuclear data and applied across a variety of research fields.

The dynamics of nuclear reactions at energies around the Coulomb barrier have been extensively studied in recent years. The resulting findings are crucial for understanding the main mechanisms involved in nuclear collisions, as well as the structure of both the projectile and the target. Angular distributions for elastic and inelastic scattering in the ${}^{12}\mathrm{C}+{}^{119}\mathrm{Sn}$ system were measured at $E_{\mathrm{Lab}}=46.9\mathrm{MeV}$. Additionally, one-neutron pickup and one-proton stripping yields were observed, and their corresponding angular distribution cross sections were determined experimentally. Coupled reaction channel calculations were performed using the double-folding São Paulo potential, providing an overall agreement with the experimental data. However, to better reproduce the elastic scattering angular distribution, it may be necessary to include additional channels in the coupling scheme.

We investigate the influence of the density curvature, skewness, kurtosis, and the higher order isoscalar and isovector coefficients of the density and isospin dependence of the equations of state (EOSs) of nuclear matter (NM) to the structure properties of neutron stars (NSs). We consider nuclear EOSs derived from the semi-realistic M3Y nucleon-nucleon interaction, which describes NM of increasing stiffness, characterized by isoscalar incompressibility $K_0=150-330\mathrm{MeV}$. We find that increasing $K_0$ and the fourth-order skewness coefficient $Q_4$, and decreasing the negativity of the isoscalar $Q_0$ and kurtosis $H_0$ coefficients and that of the isovector $K_4, I_2, G_2$, and $K_{\tau 4}$ coefficients, increases the estimated NS radius, its tidal deformability, tidal Love number of the NS ($M\ge {\text{M}}_{\odot }$), and the speed of sound ($v_s$) through the center of the NS ($\le$ 1.4 ${\text{M}}_{\odot }$), as well as the maximum mass $M_{\max }$ (NS) predicted based on a given EOS, and its corresponding maximum compactness and surface redshift $z_{\text{surf}}$ ($M_{\max }$), but this indicates less compactness and $z_{\text{surf}}$ of a given NS, and less minimum tidal Love number $k_{2,\min }$ ($M_{\max }$) and tidal deformability ${\mathrm{\Lambda }}_{\min }$ ($M_{\max }$). Meanwhile, increasing the $I_0, G_0, Q_2, K_6, H_2$, and $K_{\tau 6}$ (decreasing the negativity of the $K_2$ and $K_{\tau 2}$) coefficients inverts the behavior of the NS quantities with $K_0$ and with the aforementioned coefficients. The values of the mentioned coefficients are estimated based on combined constraints from the observed NS masses, the causality condition on $v_s$, the threshold proton fraction needed for a direct Urca process, and those given on the NM pressure from matter flow data. The values of the isoscalar (quadratic isovector) incompressibility, skewness, and kurtosis coefficients anticipated from these combined constraints are $K_0=260\pm 20\mathrm{MeV}$ ($K_2=-28\pm 4\mathrm{MeV}$), $Q_0=-361\pm 127\mathrm{MeV}$ ($Q_2=403\pm 23\mathrm{MeV}$), and $I_0=992\pm 402\mathrm{MeV}$ ($I_2=-4849\pm 49\mathrm{MeV}$), and the isobaric isospin-asymmetry coefficients of incompressibility are estimated to be $K_{\tau 2}=-248\pm 33\mathrm{MeV}, -46\le K_{\tau 4}$ (MeV) $\le$ 34, and $K_{\tau 6}=-38\pm 6\mathrm{MeV}$.

The minimal masses and radii of proto-neutron stars during different stages of their evolution are investigated. In our work we focus on two stages, directly after the supernova shock wave moves outwards, where neutrinos are still captured in the core and the lepton per baryon ratio is fixed to $Y_L=0.4$, and a few seconds afterwards, when all neutrinos have left the star. All nuclear equations of state used for this purpose fulfill the binding energy constraints from chiral effective field theory for neutron matter at zero temperature. We find for the neutrino-trapped case higher minimal masses than for the case when neutrinos have left the proto-neutron star. Thermal effects, here in the form of a given constant entropy per baryon $s$, have a smaller effect on increasing the minimal mass. The minimal proto-neutron star mass for the first evolutionary stage with $Y_L=0.4$ and $s=1$ amounts to $M_{\text{min}}\sim 0.62{\mathrm{M}}_{\odot }$ and for the stage without neutrinos and $s=2$ to $M_{\text{min}}\sim 0.22{\mathrm{M}}_{\odot }$ rather independent on the nuclear equation of state used. We also study the case related to an accretion induced collapse of a white dwarf where the initial lepton fraction is $Y_L=0.5$ and observe large discrepancies in the results of the different tables of nuclear equations of state used. Our finding points towards a thermodynamical inconsistent treatment of the nuclear liquid-gas phase transition for nuclear equations of state in tabular form demanding a fully generalized three-dimensional Gibbs construction for a proper treatment. Finally, we demonstrate that there is a universal relation for the increase of the proto-neutron star minimal mass with the lepton fraction for all nuclear equations of state used.

The present work deals with the $e^{+}\text{−}{e}^{-}$ pair production in the ${}^2\mathrm{H}(p,e^{+}{e}^{-}){}^3\mathrm{He}$ and ${}^2\mathrm{H}(n,e^{+}{e}^{-}){}^3\mathrm{H}$ processes, in order to make evident possible effects due to the exchange of a hypothetical low-mass boson, the so-called X17. These processes are studied for energies of the incident beams in the range 18–30 MeV, in order to have a sufficient energy to produce such a boson, whose mass is estimated to be around 17 MeV. We first analyze them as purely electromagnetic processes, in the context of a state-of-the-art approach to nuclear strong-interaction dynamics and nuclear electromagnetic currents, derived from chiral effective field theory ($\chi \mathrm{EFT}$). Next, we examine how the exchange of a hypothetical low-mass boson would impact the cross sections for such processes. We consider several possibilities: that this boson is either a scalar, pseudoscalar, vector, or axial particle. The main aim of the study is to exploit the specular structure of the ${}^3\mathrm{He}$ and ${}^3\mathrm{H}$ nuclei to investigate the isospin dependency of the X17-nucleon interaction, as the alleged “protophobicity.”

We discuss various methods for determining the level shifts induced by short-range interactions in exotic atoms, which are formed by a hadron and a nucleus of opposite charge. The energy shifts can be related to the effective range parameters through Deser or Trueman formulas. In order to assess the accuracy and the reliability of this indirect approach, its predictions are compared with direct bound-state calculations. Notably, the importance of including the Coulomb potential in scattering calculations is highlighted. Finally, the impact of multipole terms in the asymptotic electromagnetic interaction is examined. It is demonstrated that an indirect approach remains relevant by accounting for these effects perturbatively.

Several instances of anomalously low values of the $\frac{B(E2;4_1^{+}\to 2_1^{+})}{B(E2;2_1^{+}\to 0_{\mathrm{gs}}^{+})}$ ratio $\left(B_{4/2}\right)<1$ have previously been observed in several nuclei among the highly neutron deficient W-Os-Pt isotopes with even numbers of neutrons and protons. The relatively large number of cases suggests a striking new phenomenon that currently has no theoretical explanation. A clue to its origin might be achieved by comparing the $B_{4/2}$ ratios in even-even nuclei with the corresponding ratios of transition rates in neighboring odd-mass nuclei. However, until now only one case (${}^{169}\mathrm{Os}$) has been observed with an unusually low corresponding $B_{4/2}$ ratio, approximately $1\sigma$ below 1. Electromagnetic transition rates between excited states in the extremely neutron deficient nuclide ${}^{167}\mathrm{Os}$ were measured using 15 single-crystal germanium detectors from the jurogam 3 array coupled to the RITU gas-filled separator. The excited states of interest were populated via the ${}^{92}\mathrm{Mo}({}^{78}\mathrm{Kr},2\mathrm{pn})$ fusion-evaporation reaction and studied by selecting the rare reaction channel via recoil-$\alpha$-decay tagging. The lifetimes of low-lying states were measured using the recoil distance Doppler shift method with the APPA plunger device. From the measured lifetimes in the rotational-like band structure assigned to the $\nu i_{13/2}$ yrast intruder configuration, the $B(E2;17/2^{+}\to 13/2^{+})$ and $B(E2;21/2^{+}\to 17/2^{+})$ values were deduced, resulting in the ratio $\frac{B(E2;21/2^{+}\to 17/2^{+})}{B(E2;17/2^{+}\to 13/2^{+})}=0.49\left(10\right)$. The results were compared with previous measurements in the Os isotopic chain and theoretical mean-field calculations, implying that the odd neutron valence particle has limited, if any, influence on the $B_{4/2}$ values for this particular single-particle configuration.