The ${}^{13}\mathrm{C}(p,\gamma ){}^{14}\mathrm{N}$ reaction is the second reaction of the CNO cycle. This cycle takes place in our Sun and fuels massive, red, and asymptotic giant branch stars. The ${}^{13}\mathrm{C}(p,\gamma ){}^{14}\mathrm{N}$ rate affects the final abundances of ${}^{12,13}\mathrm{C}$ and ${}^{19}\mathrm{F}$ nuclides, with impact on our understanding of the $i$ and $s$ process, giant star nucleosynthesis and mixing processes, and ultimately the chemical evolution of the galaxy. Here, we report on a new measurement of the ${}^{13}\mathrm{C}(p,\gamma ){}^{14}\mathrm{N}$ cross section, which has been performed at the Felsenkeller shallow underground laboratory in Dresden (Germany). The present $S$-factor results agree at low energy with LUNA data but are about 20% lower than previous literature data over the whole energy range explored, $E=310-680\mathrm{keV}$. The narrow resonance corresponding to the 7966.9(5) keV excited state has been investigated and we report a new resonance strength, $\omega \gamma =18\left(2\right)\mathrm{meV}$. In addition, a new $R$-matrix fit is presented, from which new parameters for the broad resonance corresponding to the 8062.0(10) keV excited state are derived and a new extrapolation for the total $S$ factor down to zero energy is obtained, $S_{\mathrm{tot}}\left(0\right)=6.4\left(4\right)\mathrm{keV}$ b. Finally a new reaction rate is calculated and reported here.

The calculation of the spectrum of antineutrinos (${\overline{\mathrm{\nu }}}_{\mathrm{e}}$) from a reactor is a complicated problem requiring several nuclear data and physics inputs. Many of these have been investigated thoroughly to improve calculations and properly account for uncertainties. One input which has heretofore escaped consideration is the fission-yield distribution between ground and isomeric states. In this work, we explore the effect of incorporating newly evaluated isomeric yield ratios (IYR) for 43 fission products into summation calculations and identify the disproportionate importance of certain isotopes, particularly at higher energies. Our analysis indicates that updated IYRs contribute to a significant increase in the ${\overline{\mathrm{\nu }}}_{\mathrm{e}}$ spectrum around and above 7 MeV, with increases of more than 50% at higher energies. Through a detailed sensitivity study, we highlight a number of isotopes for which the IYR has a substantial effect on the ${\overline{\mathrm{\nu }}}_{\mathrm{e}}$ spectrum. This work stresses the critical role of isomeric yields in calculations of reactor ${\overline{\mathrm{\nu }}}_{\mathrm{e}}$ spectra and points to the necessity for their accurate experimental determination, especially for key fission products, in order to refine our understanding and address the observed anomalies between measured and calculated ${\overline{\mathrm{\nu }}}_{\mathrm{e}}$ spectra.

Within the recently developed five-dimensional Langevin approach for the description of fission of heavy nuclei, we have calculated the fission fragments mass and kinetic energy distributions for the fission of ${}^{180}\mathrm{Hg}$ and ${}^{190}\mathrm{Hg}$ formed in the reactions ${}^{36}\mathrm{Ar}+{}^{144}\mathrm{Sm}\Rightarrow {}^{180}\mathrm{Hg}$ and ${}^{36}\mathrm{Ar}+{}^{154}\mathrm{Sm}\Rightarrow {}^{190}\mathrm{Hg}$ at few excitation energies and found very good agreement between the calculated and experimental results. Special attention was paid to the accurate description of the dependence of shell effects on the excitation energy. It was shown that the effect of multichance fission on the mass distribution is noticeable only at small excitation energies. The kinetic energy distributions are more sensitive to pre-scission neutron emission.

Background: The probability per unit area for a radioactive ${}^{88}\mathrm{Zr}$ nucleus ($t_{1/2}=83.4$ d) to capture neutrons across resonance energies—the neutron-capture resonance integral ($I_{\gamma }$)—is the largest ever reported [Shusterman et al., Phys. Rev. C 103, 024614 (2021)] with a value of $2.53\left(28\right)\times {10}^6$ barns. This implies that the neutron-capture cross section is orders of magnitude larger than previously thought at energies relevant to explosive environments applications, such as nuclear astrophysics and radiochemical diagnostics of nuclear devices.

Purpose: These applications require the shape of the capture cross section across a wide energy range which has never been measured before. The unexpectedly large values of both the thermal capture cross section and resonance integral could have a large impact on applications. Thus, the determination of the ${}^{88}\mathrm{Zr}$ neutron capture cross sections over a wide energy range is important on both fundamental and applied levels.

Method: A neutron transmission experiment on ${}^{88}\mathrm{Zr}$ [Stamatopoulos et al., Phys. Rev. Lett. 134, 112702 (2025)] was performed at the Device for Indirect Capture Experiments on Radionuclides (DICER) at the Los Alamos Neutron Science CEnter (LANSCE), from $0.0253$ to 500 eV using the time of flight technique. Any resonances responsible for the large $(n,\gamma )$ cross section (${\sigma }_{\gamma }$), will be reflected in the ($n$,tot) cross section. The ($n$,tot) data were used to extract the capture cross section as a function of energy.

Results: The present work revealed a nuclear level in the $n+{}^{88}\mathrm{Zr}$ system at 171 meV above the neutron separation energy and a thermal neutron-capture cross section of 771(31) kb, which is in good agreement with the recently published value [Shusterman et al., Phys. Rev. C 103, 024614 (2021) and Shusterman et al., Nature (London) 565, 328 (2019)]. In contrast, the neutron-capture resonance integral extracted from the present data is 15.21(67) kb and is roughly a factor of 200 smaller than the literature value [Shusterman et al., Phys. Rev. C 103, 024614 (2021)].

Conclusions: The recently reported enormous thermal capture cross section was confirmed and is attributed to a resonance at 171 meV and bound state 174 eV below the neutron separation energy. Our obtained value of the resonance integral is 166 times smaller than reported and that can have a huge impact on applications.

High-spin isomers in very-neutron-rich $A\approx 190$ Hf-Ta-W nuclei were populated via the pioneering fragmentation of a ${}^{198}\mathrm{Pt}$ primary beam at the National Superconducting Cyclotron Laboratory. The nuclei were implanted in a Si detector stack surrounded by the Gamma-Ray Energy Tracking In-beam Nuclear Array (GRETINA) to detect delayed $\gamma$ rays, providing first level schemes using $\gamma \text{−}\gamma$ coincidence data from isomeric decays in this previously inaccessible region of the nuclear chart. A sudden transition to a strong triaxial shape is observed in the very-neutron-rich ${}^{189}\mathrm{Ta}$ $(N=116)$ nucleus from axially prolate shapes in lighter Ta isotopes, providing a critical experimental benchmark for competing theoretical predictions of nuclear-shape evolution.

The probabilities for γ-ray and particle emission as a function of the excitation energy of a decaying nucleus are valuable observables for constraining the ingredients of the models that describe the deexcitation of nuclei near the particle emission threshold. These models are essential in nuclear astrophysics and applications. In this paper, we have for the first time simultaneously measured the γ-ray and neutron emission probabilities of ${}^{208}\mathrm{Pb}$. The measurement was performed in inverse kinematics at the Experimental Storage Ring (ESR) of the GSI/FAIR facility, where a ${}^{208}\mathrm{Pb}$ beam interacted through the ${}^{208}\mathrm{Pb}(p,p^{\prime })$ reaction with a hydrogen gas jet target. Instead of detecting the γ rays and neutrons emitted by ${}^{208}\mathrm{Pb}$, we detected the heavy beamlike residues produced after γ and neutron emission. These heavy residues were fully separated by a dipole magnet of the ESR and were detected with outstanding efficiencies. The comparison of the measured probabilities with model calculations has allowed us to test and select different descriptions of the γ-ray strength function and the nuclear level density available in the literature.

Mu2e and COMET will search for electrons produced via the neutrinoless conversion of stopped muons bound in 1s atomic orbits of ${}^{27}\mathrm{Al}$, improving existing limits on charged lepton flavor violation (CLFV) by roughly four orders of magnitude. Conventionally, $\mu \to e$ conversion experiments are optimized to detect electrons originating from transitions where the nucleus remains in the ground state, thereby maximizing the energy of the outgoing electron. Clearly, detection of a positive signal in forthcoming experiments would stimulate additional work—including subsequent conversion experiments using complementary nuclear targets—to further constrain the new physics responsible for CLFV. Here we argue that additional information can be extracted without the need for additional experiments, by considering inelastic conversion in ${}^{27}\mathrm{Al}$. Transitions to low-lying nuclear excited states can modify the near-endpoint spectrum of conversion electrons, with the ratio of the elastic and inelastic responses being sensitive to the underlying CLFV operator. We extend the nuclear effective theory of $\mu \to e$ conversion to the inelastic case, which adds five new response functions to the six that arise for the elastic process. We evaluate these nuclear response functions in ${}^{27}\mathrm{Al}$ and calculate the resulting conversion-electron signal, taking into account the resolution anticipated in Mu2e/COMET. We find that ${}^{27}\mathrm{Al}$ is an excellent target choice from the perspective of the new information that can be obtained from inelastic $\mu \to e$ conversion.

The low-energy octupole $3^{-}$ state of ${}^{208}\mathrm{Pb}$ is investigated within the framework of the nuclear shell model with realistic nucleon-nucleon interactions. It is shown that the large correlation energy of this state is essentially due to the scattering of fully-aligned nucleon pairs, with the dominant role played by the scattering of high angular momentum fully-aligned neutron-proton pairs. A large fragmentation of the one-particle one-hole wave function, together with the coherence of the wave function, leads to the collective character of the octupole state. This coherence is shown to be a generic property of yrast natural-parity eigenstates of the nuclear many-body Hamiltonian. It induces a constructive accumulation of interaction strength, which may lead to a significant fragmentation of the wave function and a large correlation energy. Electric transitions from the octupole state to the ground state also benefit from this coherence property, resulting in a large enhancement of the transition probability.

We propose two novel constraints for the theoretical corrections to Gamow-Teller transition rates. The first, derived from a two-level model, predicts forbidden regions within the plane defined by the isospin-mixing correction ${\delta }_{C1}$ and the ratio $\eta$ of the isospin-symmetry Gamow-Teller matrix elements between the upper and lower admixed states. It serves as a filter for the theoretical calculations, particularly effective for small values of $\left|\eta \right|$. The other employs experimental $ft$ values, incorporating the upper admixed states, and exploits mirror symmetry to eliminate isospin-invariant and nuclear structure-independent quantities presented in the master decay formula. Within the standard model, this approach offers an alternative means for collectively testing the theoretical corrections for isospin and radiative effects beyond tree level. Additionally, it enables an experimental extraction of ${\eta }^2$, yielding a sensitive test for the isospin-conserving component of the nuclear Hamiltonian. Our investigation also reveals a substantial cancellation among radiative correction contributions in these tests, suggesting that these corrections are largely invariant under mirror symmetry. Importantly, the remarkable consistency of the nuclear structure corrections achieved in this axial-vector process provides a robust validation for the underlying theoretical approach in the purely vector process, especially the superallowed $0^{+}\to 0^{+}$ nuclear $\beta$ decay—the most accurate tool for extracting the $V_{ud}$ matrix element.

As a step towards the ultimate goal of a high-precision mass measurement of doubly magic ${}^{100}\mathrm{Sn}$, the mass of ${}^{103}\mathrm{Sn}$ was measured at the Low Energy Beam and Ion Trap (LEBIT) located at the Facility for Rare Isotope Beams (FRIB). Utilizing the time-of-flight ion cyclotron resonance technique, a mass uncertainty of 3.7 keV was achieved, an improvement by more than an order of magnitude compared to a recent measurement performed in 2023 at the Cooler Storage Ring (CSRe) in Lanzhou. Although the LEBIT and CSRe mass measurements of ${}^{103}\mathrm{Sn}$ are in agreement, they diverge from the experimental mass value reported in the 2016 version of the Atomic Mass Evaluation (AME2016), which was derived from the measured $Q_{{\beta }^{+}}$ value and the mass of ${}^{103}\mathrm{In}$. In AME2020, this indirectly measured ${}^{103}\mathrm{Sn}$ mass was classified as a “seriously irregular mass” and replaced with an extrapolated value, which aligns with the most recent measured values from CSRe and LEBIT. As such, the smoothness of the mass surface is confidently reestablished for ${}^{103}\mathrm{Sn}$. Furthermore, LEBIT's mass measurement of ${}^{103}\mathrm{Sn}$ enabled a significant reduction in the mass uncertainties of five parent isotopes which are now dominated by uncertainties in their respective $Q$ values.

Mass measurements with the ISOLTRAP mass spectrometer at CERN-ISOLDE improve mass uncertainties of neutron-deficient tin isotopes towards doubly magic ${}^{100}\mathrm{Sn}$. The mass uncertainty of ${}^{103}\mathrm{Sn}$ was reduced by a factor of 4, and the new value for the mass excess of $-67104\left(18\right)\mathrm{k}\mathrm{e}\mathrm{V}$ is compared with nuclear ab initio and density functional theory calculations. Based on these results and local trends in the mass surface, the masses of ${}^{101,103}\mathrm{Sn}$, as determined through their $Q_{\text{EC}}$ values, were found to be inconsistent with the new results. From our measurement for ${}^{103}\mathrm{Sn}$, we extrapolate the mass excess of ${}^{101}\mathrm{Sn}$ to $-60005\left(300\right)\mathrm{k}\mathrm{e}\mathrm{V}$, which is significantly less bound than previously suggested. By correcting the mass values for ${}^{101,103}\mathrm{Sn}$, we also adjust the values of ${}^{104}\mathrm{Sb}, {}^{105,107}\mathrm{Te}, {}^{108}\mathrm{I}, {}^{109,111}\mathrm{Xe}$, and ${}^{112}\mathrm{Cs}$ near the proton drip line which are connected through their $\alpha$ and proton $Q$ values. The results show an overall smoothening of the mass surface, suggesting the absence of deformation energy above the $N=50$ shell closure.

The equation of state of nuclear matter, momentum dependence of the effective interaction and in-medium modification of elastic nucleon-nucleon cross sections are studied by comparing theoretical predictions for stopping, directed, and elliptic flows of protons and light clusters in intermediate-energy heavy-ion collisions of beam energy between 150 and 800 MeV per nucleon to experimental data gathered by the FOPI Collaboration. To that end, the dcQMD transport model was upgraded by implementing medium modifications of differential elastic cross sections guided by microscopical model calculations, a medium modification factor of elastic transition amplitudes that depends on the local density, isospin asymmetry, and isospin projection of the scattering particles, a MST coalescence algorithm applied at the local freeze-out rather than at the end of simulation and threshold effects for elastic scattering. A multivariate analysis that takes into account systematic uncertainties induced on model predictions by the coalescence afterburner leads to the following constraint for the equation of state at 68% confidence level: compressibility modulus of isospin symmetric matter $K_0={230}_{-11}^{+9}\mathrm{MeV}$ and slope of the symmetry energy $L={63}_{-13}^{+10}\mathrm{MeV}$. The momentum dependence of the isoscalar potential is found to be similar to that of the empirical optical potential, with an effective isoscalar mass $m^{*}=0.{695}_{-0.018}^{+0.014}$. The isovector potential displays a momentum dependence corresponding to a positive neutron-proton effective mass difference $\mathrm{\Delta }{m}_{np}^{*}=(0.{17}_{-0.09}^{+0.10})\delta$, close to the world average for this quantity. A suppression of elastic nucleon-nucleon cross sections in symmetric nuclear matter at saturation by about $60\%$ relative to vacuum values is deduced, in qualitative agreement with microscopical results. A strong dependence of the suppression factor on isospin asymmetry is evidenced, experimental data for isospin symmetric systems proving crucial for this last conclusion.

The PHENIX experiment measured the centrality dependence of two-pion Bose-Einstein correlation functions in $\sqrt{s_{NN}}=200\mathrm{GeV} \mathrm{Au}+\mathrm{Au}$ collisions at the Relativistic Heavy Ion Collider at Brookhaven National Laboratory. The data are well represented by Lévy-stable source distributions. The extracted source parameters are the correlation-strength parameter $\lambda$, the Lévy index of stability $\alpha$, and the Lévy-scale parameter $R$ as a function of transverse mass $m_T$ and centrality. The $\lambda \left(m_T\right)$ parameter is constant at larger values of $m_T$, but decreases as $m_T$ decreases. The Lévy-scale parameter $R\left(m_T\right)$ decreases with $m_T$ and exhibits proportionality to the length scale of the nuclear overlap region. The Lévy exponent $\alpha \left(m_T\right)$ is independent of $m_T$ within uncertainties in each investigated centrality bin, but shows a clear centrality dependence. At all centralities, the Lévy exponent $\alpha$ is significantly different from that of Gaussian ($\alpha =2$) or Cauchy ($\alpha =1$) source distributions. Comparisons to the predictions of Monte-Carlo simulations of resonance-decay chains show that, in all but the most peripheral centrality class (50%–60%), the obtained results are inconsistent with the measurements, unless a significant reduction of the in-medium mass of the ${\eta }^{\prime }$ meson is included. In each centrality class, the best value of the in-medium ${\eta }^{\prime }$ mass is compared to the mass of the $\eta$ meson, as well as to several theoretical predictions that consider restoration of ${\text{U}}_A\left(1\right)$ symmetry in hot hadronic matter.

A comparative study of the equation of state for pure neutron matter and symmetric nuclear matter is presented using three ab initio methods based on diagrammatic expansions: coupled-cluster theory, self-consistent Green's functions, and many-body perturbation theory. We critically evaluate these methods by employing different chiral potentials at next-to-next-to-leading-order (NNLO)—all of which include both two- and three-nucleon contributions—and by exploring various many-body truncations. Our investigation yields highly precise results for pure neutron matter and robust predictions for symmetric nuclear matter, particularly with soft interactions. Moreover, the new calculations demonstrate that the ${\mathrm{NNLO}}_{\mathrm{sat}}\left(450\right)$ and $\mathrm{\Delta }{\mathrm{NNLO}}_{\mathrm{go}}\left(394\right)$ potentials are consistent with the empirical constraints on the saturation point of symmetric nuclear matter. Additionally, this benchmark study reveals that diagrammatic expansions with similar architectures lead to consistent many-body correlations, even when applied across different methods. This consistency underscores the robustness of the diagrammatic approach in capturing the essential physics of nucleonic systems.

We present quantum Monte Carlo calculations of magnetic moments, form factors, and densities of $A\le 10$ nuclei within a chiral effective field theory approach. We use the Norfolk two- and three-body chiral potentials and their consistent electromagnetic one- and two-nucleon current operators. We find that two-body contributions to the magnetic moment can be large (up to $\approx 33\%$ in $A=9$ systems). We study the model dependence of these observables and place particular emphasis on investigating their sensitivity to using different cutoffs to regulate the many-nucleon operators. Calculations of elastic magnetic form factors for $A\le 10$ nuclei show excellent agreement with the data out to momentum transfers $q\approx 3{\mathrm{fm}}^{-1}$.

Nuclear fission at barrier-top energies is conventionally modeled by a one-dimensional Schrödinger equation applied to internal fission channels, but that treatment is hard to justify in the configuration-interaction approach to nuclear Hamiltonians. Here we show that inclusion of states of finite momentum by the generator coordinate method (GCM) considerably extends the range of energies at which GCM-based Hamiltonians could reproduce the Schrödinger treatment. The transmission probabilities for crossing the barrier are calculated by a discrete version of Kohn's variational method, which may also be useful for other systems of interacting fermions.

Radiative corrections are essential for an accurate determination of $V_{ud}$ from superallowed $\beta$ decays. In view of recent progress in the single-nucleon sector, the uncertainty is dominated by the theoretical description of nucleus-dependent effects, limiting the precision that can currently be achieved for $V_{ud}$. In this work, we provide a detailed account of the electroweak corrections to superallowed $\beta$ decays in effective field theory (EFT), including the power counting, potential and ultrasoft contributions, and factorization in the decay rate. We present a first numerical evaluation of the dominant corrections in light nuclei based on quantum Monte Carlo methods, confirming the expectations from the EFT power counting. Finally, we discuss strategies how to extract from data the low-energy constants that parametrize short-distance contributions and whose values are not predicted by the EFT. Combined with advances in ab initio nuclear-structure calculations, this EFT framework allows one to systematically address the dominant uncertainty in $V_{ud}$, as illustrated in detail for the ${}^{14}\mathrm{O}\to {}^{14}\mathrm{N}$ transition.

We present event-by-event simulations for central asymmetric $\text{light}+\text{heavy}$ and $\mathrm{Au}+\mathrm{Au}$ collisions to investigate the formation and evolution of vortex-ring structures in the longitudinal flow velocity profile. The production-plane polarization of $\mathrm{\Lambda }$ hyperons, defined with respect to the $\mathrm{\Lambda }$ momentum and the beam, can track the “vortex-ring” feature in the event, a characteristic vortical structure generated by longitudinal flow gradients. We make comprehensive model predictions for the rapidity-dependent vortex-ring observables for different collision system sizes at $\sqrt{s_{NN}}=200$ and 72 GeV. Our predictions at the latter energy can be explored in the future LHCb fixed-target experiment at the Large Hadron Collider.

We investigate the charge and point-proton radii of Ca nuclei in detail using a density functional theory framework. The Fayans energy density functional (EDF) provides a characteristic $N$ dependence, successfully describing the parabolic behavior of the differential charge radii in $20\le N\le 28$. We focus on its physical origin by decomposing it into radial and orbital contributions. The results are compared with those of the Skyrme plus normal pairing functional, which is considered as a representative of the usual EDFs. The enhancement of the differential charge radii in $N<20$ with the Fayans functional, which contradicts the data, has the origin common to the parabolic behavior in $20\le N\le 28$. It is important to describe both $N$ regions simultaneously.

We calculate the magnetic dipole $\gamma$-ray strength functions in a chain of even-mass neodymium isotopes ${}^{144–152}\mathrm{Nd}$ in the framework of the configuration-interaction (CI) shell model. We infer the strength function by applying the maximum entropy method (MEM) to the exact imaginary-time response function calculated with the shell-model Monte Carlo (SMMC) method. The success of the MEM depends on the choice of a good strength function as a prior distribution. We investigate two choices for the prior strength function: the static path approximation (SPA) and the quasiparticle random-phase approximation (QRPA). We find that the QRPA is a better approximation at low temperatures (i.e., near the ground state), while the SPA is a better choice at finite temperatures. We identify a low-energy enhancement (LEE) in the MEM deexcitation $M1$ strength functions of the even-mass neodymium isotopes and compare with recent experimental results for the total deexcitation $\gamma$-ray strength functions. The LEE is already seen in the SPA strength function but not in the QRPA strength function, indicating the importance of large-amplitude static fluctuations around the mean field in reproducing the LEE. Our method is currently the only one that can reproduce LEE in heavy open-shell nuclei where conventional CI shell-model calculations are prohibited. With the onset of deformation as number of neutrons increases along the chain of neodymium isotopes, we observe that some of the LEE strength transfers to a low-energy excitation, which we interpret as a finite-temperature scissors mode. We also observe a finite-temperature spin-flip mode.