We take the first step towards incorporating compound nuclear observables at astrophysically relevant energies into the experimental evidence used to constrain optical models, by propagating the uncertainty in two global optical potentials, one phenomenological and one microscopic, to correlated fission observables using the Monte Carlo Hauser-Feshbach formalism. We compare to a wide range of historic and recent experimental fission measurements, and discuss in detail regions of disagreement. We find that the parametric optical model uncertainty in neutron-fragment correlated observables involving neutron energy is significant. On the other hand, we observe that other experimental features, particularly neutron-fragment correlations near the ${}^{132}\mathrm{Sn}$ shell closure and the high energy component of neutron spectra, are unlikely to be explained by the optical potential, and will require further experimental and theoretical effort to explain.

We investigate the impacts of nuclear $\alpha$-clustering structures and nucleon-nucleon cross section on nuclear stopping power for ${}^{16}\mathrm{O} + {}^{40}\mathrm{Ca}$ collisions below 300 MeV/nucleon using an extended quantum molecular dynamics (EQMD) model. Our results show that the specific $\alpha$-clustering configurations of ${}^{16}\mathrm{O}$ including chain, square, kite, and tetrahedron have a significant effect on collision dynamics. Among them, the tightly bound tetrahedral structure exhibits the highest stopping power. Moreover, the repulsive Coulomb interaction is found to reduce the stopping power of protons in the Fermi-energy domain. At higher energies, the decreasing trend is influenced by both the nucleon-nucleon cross section and the mean field.

The transverse-momentum differential radial flow observable $v_0\left(p_T\right)$, recently proposed and measured by the ATLAS and ALICE Collaborations, provides a novel tool to probe radial expansion dynamics in high-energy heavy-ion collisions. In this work, we conduct a detailed study of $v_0\left(p_T\right)$ using a blast-wave model that incorporates hydrodynamic-like expansion and thermal emission. We introduce event-by-event fluctuations in the transverse expansion velocity and kinetic freeze-out temperature using Gaussian probability distributions. Our results show that increasing the mean expansion velocity leads to a clear mass ordering in $v_0\left(p_T\right)$, while fluctuations in both expansion velocity and freeze-out temperature significantly enhance the magnitude of $v_0\left(p_T\right)$, particularly at higher $p_T$. We fit blast-wave model calculations for identified hadrons ($\pi , K$, and $p$) to recent ALICE data from Pb-Pb collisions at $\sqrt{s_{NN}}=5.02$ TeV using a Bayesian parameter estimation framework. The extracted mean transverse expansion velocity decreases, while the kinetic freeze-out temperature increases, from central to peripheral collisions. Additionally, the freeze-out temperatures inferred from $v_0\left(p_T\right)$ are systematically higher than those obtained from conventional $p_T$-spectra fits, likely due to the reduced sensitivity of $v_0\left(p_T\right)$ to resonance decay contributions.

We investigate the impact of slope of the symmetry energy ($L$) on asymmetric nuclear dense matter (neutron star) characteristics, specifically focusing on the maximum mass, radius, and dimensionless tidal deformability of a canonical mass star. To this aim, we consider a set of relativistic mean field (RMF) models based on the BSRV-CPREX parametrization [Phys. Rev. C 107, 055801 (2023)] wherein the interaction between nucleons and the rho meson, quantified by $g_{\rho N}$, as well as the vector meson mixing interaction (${\omega }^2\text{−}{\rho }^2$), represented by ${\mathrm{\Lambda }}_{\omega \rho }$, are concurrently adjusted to achieve a wide range of $L$ at saturation density ${\rho }_0$ while keeping the isoscalar nuclear matter properties fixed at ${\rho }_0$. We formulate a set of equations of state (EoSs) for $\beta$-equilibrated nucleonic matter corresponding to these RMF models, employing these EoSs to examine the influence of $L$ on neutron star attributes, including maximum mass, radius, and dimensionless tidal deformability associated with canonical mass neutron stars ($1.4M_{\odot }$). The analysis of our results suggests that various neutron star characteristics have a pronounced dependence on the slope of symmetry energy. The effect of $L$ on the threshold density and mass for the onset of the direct Urca process is also examined.

The Majorana Demonstrator was an ultra-low-background experiment designed for neutrinoless double-beta decay ($0\nu \beta \beta$) investigation in ${}^{76}\mathrm{Ge}$. Located at the Sanford Underground Research Facility in Lead, South Dakota, the Demonstrator utilized modular high-purity Ge detector arrays within shielded vacuum cryostats, operating deep underground. The arrays, with a capacity of up to 40.4 kg (27.2 kg enriched to $\sim 88\%$ in ${}^{76}\mathrm{Ge}$), have accumulated the full data set, totaling 64.5 kg yr of enriched active exposure and 27.4 kg yr of exposure for natural detectors. Our updated search improves previously explored three-nucleon decay modes in Ge isotopes, setting new partial lifetime limits of $1.83\times {10}^{26}$ yr (90% confidence level) for ${}^{76}\mathrm{Ge}$($ppp$) $\to$ ${}^{73}\mathrm{Cu}$ $e^{+}{\pi }^{+}{\pi }^{+}$ and ${}^{76}\mathrm{Ge}$($ppn$) $\to$ ${}^{73}\mathrm{Zn}$ $e^{+}{\pi }^{+}$. The partial lifetime limit for the fully inclusive triproton decay mode of ${}^{76}\mathrm{Ge}$ is found to be $2.1\times {10}^{25}$ yr. Furthermore, we have updated limits for corresponding multinucleon decays.

In this work, we present a detailed analysis of the interference between meson exchange currents (MEC) and one-body currents in quasielastic electron scattering, with a focus on the sign of this interference in the transverse response for one-particle emission. We prove that the interference of both the Delta and pion-in-flight currents with the one-body current is negative, leading to a partial cancellation with the seagull current. This is mathematically demonstrated within the framework of the Fermi gas model. By comparing these interferences across various independent particle models, both relativistic and nonrelativistic, our results indicate that all studied models display the same behavior.

We analyze joint factorial cumulants of protons and antiprotons in relativistic heavy-ion collisions and point out that they obey the scaling ${\widehat{C}}_{nm}^{p,\overline{p}}\propto {\langle N_p\rangle }^n{\langle N_{\overline{p}}\rangle }^m$ as a function of acceptance when only long-range correlations are present in the system, such as global baryon conservation and volume fluctuations. This hypothesis can be directly tested experimentally without the need for corrections for volume fluctuations. We show that if correlations among protons and antiprotons are driven by global baryon conservation and volume fluctuations only, the equality ${\widehat{C}}_2^p/{\langle N_p\rangle }^2={\widehat{C}}_2^{\overline{p}}/{\langle N_{\overline{p}}\rangle }^2$ holds for large systems created in central collisions. We point out that the experimental data of the STAR Collaboration from phase I of the Relativistic Heavy Ion Collider (RHIC) beam energy scan (BES) are approximately consistent with the scaling ${\widehat{C}}_{nm}^{p,\overline{p}}\propto {\langle N_p\rangle }^n{\langle N_{\overline{p}}\rangle }^m$, but the normalized antiproton correlations are stronger than those of protons, $-{\widehat{C}}_2^{\overline{p}}/{\langle N_{\overline{p}}\rangle }^2>-{\widehat{C}}_2^p/{\langle N_p\rangle }^2$. Existing theoretical baselines, based on global baryon conservation and volume fluctuations, cannot explain the data, which we refer to as the antiproton puzzle. We also discuss high-order factorial cumulants which can be measured with sufficient precision within phase II of RHIC-BES.

We calculate the two-body triton photodisintegration cross section as a function of photon energy to next-to-next-to leading order (NNLO) in pionless effective field theory [EFT($\cancel{\pi }$)] and show good agreement with experiment. In addition we calculate the polarization asymmetry $R_C=-0.441\left(15\right)$ in cold neutron-deuteron capture to NNLO in EFT($\cancel{\pi }$), in agreement with the experimental value of $R_C=-0.42\pm 0.03$ [Konijnenberg et al., Phys. Lett. B 205, 215 (1988)]. We also assess the dependence of $R_C$ on different fits of the two-nucleon magnetic currents. Finally, we consider the impact of Wigner-SU(4) symmetry and demonstrate that starting from the Wigner-SU(4) symmetric limit and including perturbative corrections to the breaking of Wigner-SU(4) symmetry does a good job of describing two-body triton photodisintegration.

Applications of reduced basis method emulators are increasing in low-energy nuclear physics because they enable fast and accurate sampling of high-fidelity calculations, enabling robust uncertainty quantification. In this paper, we develop, implement, and test two model-driven emulators based on the (Petrov-)Galerkin projection using the prototypical test case of two-body scattering with the Minnesota potential and a more realistic local chiral potential. The high-fidelity scattering equations are solved with the matrix Numerov method, a reformulation of the popular Numerov recurrence relation for solving special second-order differential equations as a linear system of coupled equations. A novel error estimator based on reduced-space residuals is applied to an active learning approach (a greedy algorithm) to choosing training samples (“snapshots”) for the emulator and contrasted with a proper orthogonal decomposition (POD) approach. Both approaches allow for computationally efficient offline-online decompositions, but the greedy approach requires many fewer snapshot calculations. These developments set the groundwork for emulating scattering observables based on chiral nucleon-nucleon and three-nucleon interactions and optical models, where computational speed-ups are necessary for Bayesian uncertainty quantification. Our emulators and error estimators are widely applicable to linear systems.

Background: A muonic atom, composed of a negative muon and an atomic nucleus, undergoes two primary decay processes: muon decay and muon nuclear capture. The branching ratio between these two processes can be determined from the measured lifetime of the muonic atom. While past research has examined the general trend of muon capture rates across different elements, experimental and theoretical investigations into the isotope dependence of the lifetime remain limited.

Purpose: The present study aims to measure the lifetimes of the muonic atom of isotopically enriched silicon isotopes.

Methods: The experiment was conducted at the muon facility in the Material and Life Science Facility (MLF), J-PARC. A muon beam was stopped in various target materials, including isotopically enriched ${}^{28,29,30}\mathrm{Si}$. The lifetimes of the muonic atoms were measured by detecting decay electrons using a $\mu \mathrm{SR}$ spectrometer. The decay spectra were analyzed by fitting with multiexponential functions to account for contributions from the target nucleus and surrounding materials.

Results: For the first time, the lifetimes of the muonic atom of isotopically enriched ${}^{28,29,30}\mathrm{Si}$ were measured. Additionally, seven other targets were studied to validate the experimental method and analysis procedure. The results were compared with theoretical models such as Primakoff, Goulard-Primakoff, and the recently-developed microscopic and evaporation model (MEM).

Conclusions: The Primakoff and Goulard-Primakoff formulas, while reproducing certain aspects of the isotope dependence, require further refinement. The comparison with MEM calculations constrains the axial vector ($g_A$) and induced pseudoscalar ($g_P$) coupling constants. The present experiment establishes a method for measuring the lifetimes of the muonic atom and will contribute to future systematic investigations.

We present a shell-model analysis of $N=51$ isotones, ${}^{93}\mathrm{Mo}, {}^{95}\mathrm{Ru}, {}^{97}\mathrm{Pd}$, and ${}^{99}\mathrm{Cd}$ to quantify the role of neutron-proton interactions in shaping the location and half-life of isomeric states. The study is motivated by the anomalous behavior of the ${21/2}^{+}$ isomeric state in ${}^{93}\mathrm{Mo}$, a prominent candidate for nuclear excitation by electron capture (NEEC), which misses an $E2$ decay branch due to a higher-lying ${17/2}^{+}$ state and instead proceeds via a long-lived $E4$ isomeric transition. Employing a consistent configuration space and empirically derived effective interaction, we extract and compare the proton-proton and neutron-proton matrix elements for the four $N=51$ isotones. Our results show a distinct dominance of the neutron-proton interaction in ${}^{93}\mathrm{Mo}$, in contrast to its neighbors (${}^{95}\mathrm{Ru}, {}^{97}\mathrm{Pd}$, and ${}^{99}\mathrm{Cd}$) where no analogous isomeric behavior emerges due to structural evolution. These findings reveal that the favorable structure for NEEC in ${}^{93}\mathrm{Mo}$ stems from subtle interaction systematics that do not persist across the chain. We find that the $E2$ strength of the key NEEC transition is reduced by 40% compared to the previously estimated value. The analysis provides microscopic insights into the origin of long-lived isomerism in medium-mass nuclei and outlines a framework for identifying future candidates in other mass regions for exploiting the potential energy storage capacities of isomeric states.

Despite the advancements of research on $\alpha$-decay half-lives $T_{1/2}$, accurate studies of the theoretical calculation of unfavored $\alpha$ transitions remain an open problem in nuclear physics. This paper performs a separate physical interpretation of both favored and unfavored $\alpha$ transitions by combining the deformed density-dependent cluster model (DDCM) with a Bayesian neural network (BNN). The global and extrapolated analyses demonstrate the effectiveness of the BNN in refining predictions of $T_{1/2}$, particularly for the intricate unfavored transitions. Furthermore, quantitative comparisons using the maximum information coefficient (MIC) across nine characteristic parameters within BNN inputs systematically uncover hidden nuclear structure effects inherent to both favored and unfavored $\alpha$ decays. The comparisons show that the contribution of $\alpha$-decay energy $Q_{\alpha }$ to $T_{1/2}$ is dominant in nine characteristic parameters, and the influence of deformation is conspicuous in the open-shell region. Compared to favored $\alpha$ transitions, the correlations reflected by MIC between each characteristic parameter and $T_{1/2}$ are stronger in unfavored $\alpha$ transitions, indicating its more complex internal physical mechanism. This study advances the exploration of physical interpretation of $\alpha$ transitions and provides actionable insights to guide future investigations in nuclear physics.

We theoretically investigate Cooper quartet correlations in $N=Z$ doubly-magic nuclei (${}^{40}\mathrm{Ca}, {}^{100}\mathrm{Sn}$, and ${}^{164}\mathrm{Pb}$). We first examine the quartet condensation fraction in infinite symmetric nuclear matter by using the quartet Bardeen-Cooper-Schrieffer theory. Together with the total nucleon density profiles of doubly-magic nuclei obtained from the Skyrme Hartree-Fock calculation, we discuss the spatial distribution of quartet correlations in finite nuclei within the local density approximation. Large quartet condensate fractions are found at the surface region of an atomic nucleus due to the strong neutron-proton attractive interaction responsible for the deuteron formation in vacuum. Moreover, we discuss a possible microscopic origin of the Wigner term in the context of nucleon-quartet scattering in dilute symmetric nuclear matter. The nucleon-quartet scattering effect on the Wigner term is numerically estimated to be about one order of magnitude of the total empirical strength, indicating the importance of multinucleon clusters in the symmetry energy and mass formula in addition to the neutron-proton pairing.

The deformation properties of the low-lying states in ${}^{74}\mathrm{Ge}$ have been investigated using multistep Coulomb excitation. The measurements were carried out with the advanced $\gamma$-ray tracking array, GRETINA, and the CHICO2 particle detector. A comprehensive set of $E2$ transition and diagonal matrix elements was deduced following an analysis with the semiclassical coupled-channels code GOSIA. The data were compared with results of calculations carried out within the framework of the generalized triaxial rotor model as well as with the configuration interaction shell model and the symmetric rotor model. Results from calculations with covariant density functional theory were used to construct a five-dimensional collective Hamiltonian for further comparisons with the data. Collectively, the calculations provide an accurate reproduction of the experimental matrix elements and further support an understanding in terms of the coexistence of two axially asymmetric shapes. This leads to an overall interpretation of the underlying structure of ${}^{74}\mathrm{Ge}$ requiring triaxiality, as is also the case in the neighboring even-mass Ge isotopes.

The isovector response in ${}^{12}\mathrm{B}$ was investigated via the ${}^{12}\mathrm{C}({}^{10}\mathrm{Be},{}^{10}\mathrm{B}+\gamma ){}^{12}\mathrm{B}^{*}$ reaction at $100A\mathrm{MeV}$. By utilizing the $\gamma$-decay properties of the 1.74 MeV $0^{+}$ and 0.718 MeV $1^{+}$ states in ${}^{10}\mathrm{B}$, the separate extraction of the non-spin-transfer ($\mathrm{\Delta }S=0$) and spin-transfer ($\mathrm{\Delta }S=1$) isovector responses up to an excitation energy of 50 MeV in ${}^{12}\mathrm{B}$ in a single measurement is demonstrated. The experimental setup employed the S800 spectrometer to detect and analyze the ${}^{10}\mathrm{B}$ ejectiles and the Gamma-Ray Energy Tracking In-beam Nuclear Array (GRETINA) for obtaining the Doppler-reconstructed spectrum for $\gamma$ rays emitted in flight by ${}^{10}\mathrm{B}$. A ${}^{12}\mathrm{C}$ foil was placed at the pivot point of the spectrograph. The ${}^{12}\mathrm{B}$ reaction product was not detected. Contributions from transitions associated with the transfer of different units of angular momentum in the non-spin- and spin-transfer responses were analyzed using a multipole decomposition analysis. The extracted non-spin-dipole ($\mathrm{\Delta }S=0, \mathrm{\Delta }L=1$) and spin-dipole ($\mathrm{\Delta }S=1, \mathrm{\Delta }L=1$) responses were found to be consistent with available data from other charge-exchange probes, validating the non-spin- and spin-transfer filters used. While statistical uncertainties and experimental resolutions were relatively large due to the modest intensity of the ${}^{10}\mathrm{Be}$ secondary beam, the results show that, with the much higher intensities that will be available at new rare-isotope beam facilities, the (${}^{10}\mathrm{Be},{}^{10}\mathrm{B}+\gamma$) reaction and its $\mathrm{\Delta }{T}_z=-1$ partner, the (${}^{10}\mathrm{C},{}^{10}\mathrm{B}+\gamma$) reaction, are powerful tools for elucidating the isovector non-spin- and spin-transfer responses in nuclei.

The ratio of volume and surface symmetry energy coefficients, $\kappa =E_{\mathrm{sym}}^V/E_{\mathrm{sym}}^S$, is investigated using the difference of the mirror pair root-mean-square charge radii ($R_{\mathrm{ch}}$), $\mathrm{\Delta }{R}_{\mathrm{ch}}^{\mathrm{mir}}$, with the aid of an improved Bayesian neural network (BNN) method with the explicit considerations of the BNN parametrization uncertainties and the experimental uncertainties in the training phase. The BNN method proves to have a robust predictive capability both in reproducing the existing $R_{\mathrm{ch}}$ data and in extrapolating the unmeasured data. Among all $A\ge 30$ isotopes with available experimental masses, 60 mirror pairs, of which 52 pairs contain at least one unmeasured nucleus, are found, and their $\mathrm{\Delta }{R}_{\mathrm{ch}}^{\mathrm{mir}}$ values are calculated using the BNN-predicted $R_{\mathrm{ch}}$ values. Within the droplet model by Myers and Swiatecki, $\kappa$ is deduced to be $\kappa =3.2_{-0.7}^{+1.0}$ from the obtained $\mathrm{\Delta }{R}_{\mathrm{ch}}^{\mathrm{mir}}$ values. This $\kappa$ value agrees well with $\kappa =3.0_{-0.5}^{+0.5}$ deduced from the neutron skin ($\mathrm{\Delta }{R}_{np}$) data in this work within the error, demonstrating the feasibility of our aim to investigate $\kappa$ using $\mathrm{\Delta }{R}_{\mathrm{ch}}^{\mathrm{mir}}$ with the aid of the BNN method. Our results, both from the predicted $\mathrm{\Delta }{R}_{\mathrm{ch}}^{\mathrm{mir}}$ and from the neutron skin data, are further compared with those from previous analyses of experimental observables, such as nuclear mass, $\mathrm{\Delta }{R}_{np}$, and isobaric analog states (IAS). It is found that our results show close agreement with those from the previous analyses of $\mathrm{\Delta }{R}_{np}$, IAS, and their combination, converging tightly around $\kappa \approx 3.1$, and are systematically larger than those obtained with the incorporation of nuclear mass data, $\kappa \approx 2.2$. Such a significant difference between the results unrelated to mass and those related to mass is briefly discussed.

An isomeric state with $T_{1/2}=1.46\left(10\right)\mu \mathrm{s}$ and $E_x=8835$ keV has been established in ${}^{207}\mathrm{Pb}$. This state likely arises from the occupation of neutron holes in the high-$j i_{13/2}$ and $j_{15/2}$ subshells following the excitation of the ${}^{208}\mathrm{Pb}$ core. The high-spin excited level structure of ${}^{207}\mathrm{Pb}$ has been extended beyond the previously known states up to $E_x\approx$ 6 MeV. Additionally, a more precise value of the half-life of the $I^{\pi }$ = ${10}^{+}$ isomer in ${}^{208}\mathrm{Pb}$ has been obtained. Shell-model calculations provide a good account of the structure up to the $31/2^{+}$ level in ${}^{207}\mathrm{Pb}$, while the energies of higher-spin states built from exclusively high-$j$ nucleons are considerably underestimated.

A unified description of charge radii throughout the entire nuclide chart plays an essential role for our understanding of nuclear structure and fundamental nuclear interactions. In this work, the influence of new term, which catches the spirit of neutron- and proton-pair condensation around Fermi surface, on the charge radii has been investigated based on the Skyrme density functionals with effective forces SLy5 and ${\mathrm{SkM}}^{*}$. The differential charge radii of even-even Ca, Ni, Sn, and Pb isotopes are employed to evaluate the validity of this theoretical model. Meanwhile, the results obtained by relativistic density functional with effective Lagrangian NL3 are also shown for the quantitative comparison. Calculated results suggest that the modified model can improve the trend of changes of differential charge radii along Ca, Ni, Sn, and Pb isotopic chains, especially the shell closure effect at neutron numbers $N=28$, 82, and 126. The shell quenching phenomena of charge radii can also be predicted at neutron number $N=50$ along Ni and Sn isotopes, respectively. The inverted parabolic-like shapes between two fully filled shells can also be observed, but the amplitude is gradually weakened from Ca to Pb isotopic chains. Combining the existing literatures, it suggests that the discontinuous behavior in nuclear charge radii can be described well by considering the influence of neutron Cooper pair condensation around Fermi surface.

We calculate the nuclear matrix element (NME), effective axial-vector current coupling $g_A^{\mathrm{eff}}$, and half-life of double-$\beta$ ($\beta \beta$) decay using the transition operator perturbed by the nuclear interaction. The correction terms for the NME are obtained by extending the hadron sector to a higher order in terms of the Rayleigh-Schrödinger perturbation theory. The NME calculations are performed for the neutrinoless $\beta \beta$ ($0\nu \beta \beta$) and the two-neutrino $\beta \beta$ ($2\nu \beta \beta$) decays of ${}^{136}\mathrm{Xe}$. The nuclear wave functions are calculated by the quasiparticle random-phase approximation (QRPA) with the Skyrme, the Coulomb, and the contact pairing interactions. Sufficiently large single-particle valence spaces are used. The correction terms for the NME are comparable with the leading term in absolute value, and the sum of the corrections has the opposite sign compared to that of the leading term. The $g_A^{\mathrm{eff}}\text{"s}$ for the $\beta \beta$ NME are calculated by a few methods depending on the truncation of the NME and the half-life referred to. Similarities are found between some of these $g_A^{\mathrm{eff}}\text{"s}$, including those of the $0\nu \beta \beta$ NME. This leads to the conclusion that the value of $g_A^{\mathrm{eff}}$ can indeed be determined by the perturbed transition operator. It is in a comparable range of the $g_A$ for the $2\nu \beta \beta$ NME. The perturbation effect on the $2\nu \beta \beta$ half-life is discussed by comparing the calculated half-lives with the different $g_A\text{"s}$ and the NME components.

This study investigates the application of deep learning models—recurrent neural networks, gated recurrent units, and long short-term memory networks—for predicting nuclear binding energies. Utilizing data from the Atomic Mass Evaluation (AME2020), we incorporate key nuclear structure features, including proton and neutron numbers, as well as additional terms from the liquid drop model and shell effects. Our comparative analysis demonstrates that the gated recurrent units model achieves a root-mean-square error (${\sigma }_{\mathrm{RMSE}}$) of 0.326 MeV, outperforming traditional regression-based approaches, such as those based on the liquid drop model, which typically yield higher errors. To assess model reliability, we validate predictions using the Garvey-Kelson relations, obtaining an error of 0.202 MeV, and further test extrapolation capabilities using the WS, WS3, WS4, DZ28, FRDM2012, and HFB25 models. The extrapolation analysis confirms the robustness of our approach, particularly in predicting binding energies for nuclei near the drip lines. These results highlight the effectiveness of deep learning in nuclear BE predictions, highlighting its potential to enhance the accuracy and reliability of theoretical nuclear models.