Charge radii differences of mirror partner nuclei provide an alternative probe to pin down the interaction components in asymmetric nuclear matter. In this work, the differences in the charge radii of almost spherical mirror-paired nuclei ${}^{54}\mathrm{Ni}\text{−}{}^{54}\mathrm{Fe}$ and ${}^{36}\mathrm{Ca}\text{−}{}^{36}\mathrm{S}$ are used to constrain the magnitude of tensor terms in the Skyrme interactions. The calculated results suggest that a linear correlation can be found between the difference of charge radii of mirror partner nuclei and the adopted strengths of the triplet-odd and triplet-even tensor components. In addition, it suggests that charge radii differences of mirror-paired nuclei are more sensitive to the adopted strengths of the triplet-odd parameter $U$ rather than the triplet-even parameter $T$. Combining the quantitative constraint strengths of the triplet-even tensor part obtained from the magnetic dipole ($M1$) excitations, the charge-exchange Gamow-Teller states, and the spin-dipole excitations, the triplet-odd strengths are further constrained for the SLy5 as well as SGII effective interactions. This provides an alternative approach to constrain the appropriate magnitude of tensor force.

The dynamical influence of $\mathrm{\Lambda }$ hyperons on the excited-state properties of closed-shell multi-$\mathrm{\Lambda }$ Ca, Ni, Sn, and Pb hypernuclei is investigated using the self-consistent Hartree-Fock $+$ Random Phase Approximation in coordinate space. The strength distributions for the isoscalar monopole, isovector dipole, and isoscalar quadrupole modes are calculated, revealing a systematic upward energy shift with increasing $\mathrm{\Lambda }$ hyperon number $-S$. The scaling behavior of the computed centroid energies $\sqrt{m_1/m_{-1}}$ with respect to both the mass and hyperon number is determined. The nuclear incompressibility modulus $K_A$ is found to increase monotonically with $-S$. The largest value is found in the ${}_{50\mathrm{\Lambda }}{}^{258}\mathrm{Pb}$ hypernucleus, reaching $K_A=322$ MeV. Calculations in uniform hypernuclear matter confirm that this stiffening is a bulk effect driven by both the $N\mathrm{\Lambda }$ and $\mathrm{\Lambda }\mathrm{\Lambda }$ interactions. Analysis of the transition densities for states with maximal collective coherence indicates that the dynamical effect of $\mathrm{\Lambda }$ hyperons is predominantly in phase with the protons, especially in the case of the isovector $E1$ modes.

We perform an ab initio quantum Monte Carlo calculation of the isospin-symmetry-breaking correction ${\delta }_C$ to the superallowed $\beta$ decay of ${}^{10}\mathrm{C}$. Using both phenomenological and chiral nuclear interactions, we evaluate the Fermi matrix element and quantify its deviation from the canonical $\sqrt{2}$ value. The resulting ${\delta }_C$ values lie in the range $\approx 0.15–0.25\%$ and are consistent, within sizable uncertainties (approximately $34\%–65\%$ relative), across Hamiltonians, indicating no statistically significant dependence on the choice of nuclear interaction. The extracted values of $V_{\text{ud}}$ are also found to be compatible with current determinations within these uncertainties.

Low-resolution nuclear Hamiltonians, obtained from chiral effective field theory (EFT) and softened using renormalization group techniques, have been very successful in nuclear structure theory. The associated EFT truncation uncertainty for these potentials is difficult to quantify. We use singular value decompositions of low-resolution nuclear forces to obtain an operator basis to study Hamiltonian uncertainties for these potentials. We perform Bayesian inference for the singular values and three-body low-energy constants, the free parameters of nuclear Hamiltonians in our framework, using likelihoods based on nucleon-nucleon phase shifts and triton observables to account for the EFT truncation uncertainties in these quantities. Validating our inference, we find good reproduction of input uncertainties for low-energy phase shifts and three-nucleon observables. On the other hand, uncertainties for higher-energy phase shifts are systematically underestimated, which we attribute to limitations of the singular value decomposition and neglected correlations between phase shifts at different energies. We propagate the resulting distribution of Hamiltonians forward to predictions for ground-state properties of ${}^{24,28}\mathrm{O}$ and ${}^{48}\mathrm{Ca}$, comparing against other state-of-the-art nuclear structure predictions. Our approach makes it possible to account for EFT uncertainties when using low-resolution potentials, which is important for many ongoing studies in exotic nuclei.

In this study, we calculate the $\gamma Z$-exchange contribution to elastic $ep$ scattering at large momentum transfer within perturbative quantum chromodynamics (pQCD). We present analytical expressions for the $\gamma Z$-exchange contributions to the amplitudes. We also estimate the asymptotic behaviors of the amplitude contributions and of the physical quantity $A_{\text{PV}}$ at high momentum transfer. These asymptotic behaviors determine the subtraction order in the dispersion relations (DRs) satisfied by the amplitudes. At high $Q^2$ beyond the forward limit, our pQCD analysis shows that this subtraction order is fixed by the high-$\nu$ behavior of the amplitude coefficients $c_i^{\gamma Z,\text{PV}}$, and that $c_{3,A}^{\gamma Z,\text{PV}}$ requires a once-subtracted DR. Within the present pQCD framework and the adopted proton distribution amplitudes, these high-energy results also provide nontrivial constraints on low-energy DR assumptions.

Background: Due to its large production cross section, ${}^{254}\mathrm{No}$ is the most-studied nucleus in the transfermium region and has been the “pioneer” nucleus in many different types of studies ranging from in-beam and decay $\gamma$-ray spectroscopy to $\gamma$-ray calorimetry. ${}^{254}\mathrm{No}$ is a well-deformed nucleus. At low excitation energy, the spins (I), parities ($\pi$), and excitation energies of three rotational bandheads are known: the $0^{+}$ ground state; a two-quasiproton $I^{\pi }=3^{+}$ state at an excitation energy of 987 keV, which decays promptly to the ground-state rotational band; and a long-lived $8^{-}$ state at 1297 keV, whose microscopic configuration is still under debate.

Purpose: This paper reexamines the electromagnetic decay of the long-lived $8^{-}$ state in ${}^{254}\mathrm{No}$ using the enhanced sensitivity to the detection of internal conversion electrons of the GABRIELA detector array installed at the focal plane of the recoil separator SHELS at the Joint Institute for Nuclear Research in Dubna.

Methods: ${}^{254}\mathrm{No}$ nuclei were produced in fusion-evaporation reactions between ${}^{48}\mathrm{Ca}$ ions and the atoms of ${}^{208}\mathrm{Pb}$ targets. The evaporation residues of interest were separated from the background of other reaction products by the recoil separator SHELS and transported to the GABRIELA decay station where the $\gamma$ as well the internal-conversion decay from the $8^{-}$ isomer could be jointly observed for the first time. Standard spectroscopy techniques together with a Geant4-assisted analysis of the spectroscopic data were used to establish the decay scheme of the $8^{-}$ isomer.

Results: The observed $\gamma$ ray and internal-conversion-electron singles and coincidence spectra have revealed new decay branches from the $8^{-}$ isomer as well as new states lying below it. A $4^{+}$ state has been established at 1203 keV above the ground sate. The presence of a $2^{-}$ octupole phonon state could also be suggested at 1114 keV. The spectrum of detected internal-conversion electrons has uncovered the existence of an intense electric monopole ($E0$) contribution stemming from the decays of one or more states lying below the $3^{+}$ state. These findings are discussed in the light of quasiparticle random-phase approximation (QRPA) based on the finite-range D1M Gogny force and a new extension of the discrete nonorthogonal shell model including a variation-after-projection approach.

Conclusions: The newly identified $4^{+}$ state is interpreted as the unfavored angular momentum coupling of two protons occupying the same single-particle configurations as the protons forming the previously known $3^{+}$ state. The two states form what is called a Gallagher-Moskowski doublet. This interpretation is supported by both the QRPA and shell-model calculations. The energy difference between the $3^{+}$ and $4^{+}$ states provides the first experimental measurement of spin splitting between two quasiproton states in the actinide region. The excess $E0$ strength evidenced by the internal-conversion-electron spectrum is attributed to the decay of members of a second $0_2^{+}$ rotational band lying at 884 keV above the ground state, which is weakly populated in the decay of the $3^{+}$ band. Remarkably, a $0_2^{+}$ state is obtained at 859 keV above the ground state in the new shell-model description of ${}^{254}\mathrm{No}$, which also reproduces the sequence and electromagnetic-decay properties of the ground-state and $3^{+}$ rotational bands.

This paper reports on the first complete shell-model description of low-lying structures of ${}^{254}\mathrm{No}$. Employing the Kuo-Herling effective interaction, the calculations are performed using the discrete nonorthogonal shell model recently implemented within the angular-momentum variation after projection applied on nonaxial wave functions. Our calculations show a striking agreement with the experimentally known spectroscopy: the yrast band, the $8^{-}$ ($K=8$), $3^{+}$ ($K=3$), and ${10}^{+}$ ($K=10$) isomers together with associated $K$ bands. We reproduce the recently measured Gallagher-Moszkowski splitting between the $3^{+}(K=3$) and $4^{+}$ ($K=4$) bandheads. We predict the appearance of a second $0^{+}$ state in excellent agreement with recent observations. In addition, we systematically examine the ground state spectra and the dipole and spectroscopic quadrupole moments of even-even, odd-even, odd-odd nuclei from $A=251$ to $A=256$, which are favorably reproduced. The present description of ${}^{254}\mathrm{No}$ shows the ability of the shell model framework to describe the low-lying properties for such an exotic nucleus at the frontier of modern experimental nuclear physics research.

In this first-of-its-kind survey conducted on heavy and deformed nuclei in the actinide region of the nuclear chart, we have charted nuclear ground state properties predicted by Fayans energy density functionals (EDFs), focusing in particularly on octupole deformability. Compared to earlier studies with Skyrme-based EDFs, we found a similar region of octupole deformed nuclei. Moreover, Fayans EDFs were found to provide accurate predictions for various ground state properties, when compared to experimental data. Comparison to Skyrme-based EDFs shows similar trends in various nuclear properties.

Properties of isomeric states and the deexcitation paths to the ground state have been observed in ${}^{165}\mathrm{W}$ and ${}^{169}\mathrm{W}$ nuclei in experiments employing fusion-evaporation reactions at the Accelerator Laboratory of the University of Jyväskylä, Finland. The $(13/2^{+})$ isomeric state in ${}^{165}\mathrm{W}$ was measured to have a half-life of $7.4\left(2\right)$µs and an excitation energy of 301.4(3) keV, while in ${}^{169}\mathrm{W}$, the $J^{\pi }=(9/2^{+})$ isomeric state at 127.2(3) keV has $t_{1/2}=7.4\left(5\right)$µs. The observed hindrance factors are 6.9(2) for the $M2$ deexciting transition in ${}^{165}\mathrm{W}$ and $2.29\left(15\right)\times {10}^6$ for the $E1$ deexciting transition in ${}^{169}\mathrm{W}$, of which the former is a typical value in this region, while the latter is an order of magnitude larger than most other similar cases. The excited- and ground-state spin assignments are discussed.

A study of the $N=89$ odd-odd nucleus ${}^{150}\mathrm{Pm}$ with the ${}^{152}\mathrm{Sm}(d,\alpha )$ reaction at 18 MeV incident energy is presented. A distorted-wave Born approximation (DWBA) analysis of measured angular distributions has been performed for 48 states observed in this nucleus up to $E_x\approx 1.4$ MeV, yielding information on their possible spin and parity values. Albeit not unique due to inherent ambiguities of the DWBA analysis, these assignments are the only ones existing now for this nucleus, for which $J^{\pi }$ values were previously proposed for only two states. A comparison of the observed states is made with theoretical calculations, performed with the Interacting boson-fermion-Fermion Model-2, and the Shell Model, respectively. These results are a first step to a better understanding of the structure of the odd-odd nuclei around the shape phase transition critical point at $N=90$.

An yrast, $J^{\pi }=5^{-}$, spin-trap isomer has been previously identified in ${}^{32}\mathrm{Si}$. The isomeric state decays predominantly via a hindered $E3$ transition [$B$($E3$) = 0.0841(10) W.u.], bypassing a nearby $E2$ decay path to the first excited $3^{-}$ level. The single-neutron aspects of these negative-parity levels were investigated via the ${}^{31}\mathrm{Si}\left(d,p\right){}^{32}\mathrm{Si}$ reaction at 9.6 MeV/u using HELIOS and the ATLAS in-flight facility. The $5^{-}$ state appears as a dominant $\ell =3$ transfer with a relatively large spectroscopic factor, confirming its single-particle $\nu 0f_{7/2}$ character. The yrast $3^{-}$ level had a reduced $\ell =3$ spectroscopic factor of approximately 0.44 compared with that of the $5_1^{-}$ level. This is similar to the situation observed in nearby ${}^{34}\mathrm{S}$, which by contrast has a measured $B$($E2,5^{-}\to 3^{-}$) transition strength closer to 1 W.u. It has been concluded that the hindrance of the $5_1^{-}\to 3_1^{-}$ transition in ${}^{32}\mathrm{Si}$ is not primarily due to the differing overlaps in the neutron structure. Instead, the lack of participation by both the protons and the neutrons in the transition is proposed as the transition-strength-reduction mechanism.

We quantify to what degree the QCD matter created in high-energy oxygen-oxygen ($\mathrm{O}+\mathrm{O}$) collisions at $\sqrt{s_{NN}}=5.36$ TeV reaches a locally equilibrated state. For this purpose, we employ a novel framework based on the core-corona picture that describes the dynamics of both locally equilibrated fluids (the core) and nonequilibrium particles (the corona). Contributions from the core become larger than those from the corona above charged-particle multiplicity at midrapidity, ${\langle d{N}_{\mathrm{ch}}/d\eta \rangle }_{\left|\eta \right|<0.5}\approx 20$. We also find that non-negligible contributions from the corona still remain even in central $\mathrm{O}+\mathrm{O}$ collisions. The yield ratios of strange baryons to charged pions exhibit an increasing behavior with increasing multiplicity at midrapidity. However, these ratios are smaller than those obtained when assuming that QCD matter has reached complete chemical equilibrium. These results demonstrate that a purely hydrodynamic approach is insufficient and that the inclusion of a corona component is essential for describing the dynamics of intermediate-size systems such as $\mathrm{O}+\mathrm{O}$ collisions.

An outstanding puzzle in the structure of very heavy nuclei lies in the rotation response of deformed transuranic isotopes. While the rotation alignment of pairs of $i_{13/2}$ protons is ubiquitous and well understood, observing the analogous alignment of the $j_{15/2}$ neutrons has been elusive. In this work we present a new quantitative analysis approach: from their moments of inertia as a function of frequency, we compare the alignments of rotational bands with both “low” and high-$j$ intrinsic structures in the $N=151$ isotones of Pu, Cm, Cf, and No, thereby distinguishing between the alignments of neutron versus proton pairs through “blocking” effects. In this way, the alignment of $j_{15/2}$ neutrons can be clearly identified for the first time. The protons and neutrons begin aligning at a very similar frequency. The contribution of $j_{15/2}$ neutrons to the total alignment is found to grow with increasing $Z$ compared to $i_{13/2}$ protons. To explain these observations, it is necessary to adopt a self-consistent set of single-particle energies corresponding to the nuclear shape that minimizes the mass. The shape description needs to include high-order deformations up to at least ${\beta }_6$.

Employing the relativistic continuum Hartree-Bogoliubov (RCHB) theory with intrinsic electromagnetic structure corrections, this work primarily investigates the charge properties of halo nuclei along the Ne and P isotopic chains. Our results characterize halo nuclei by an extended tail in the charge density and distinct signatures in the charge form factors at low momentum transfer. Moreover, the higher-order radial moments of nuclear charge density, particularly the eighth moment, exhibit pronounced oscillations, serving as a key indicator of the neutron halo structure. These special features in nuclear charge distributions will serve as key references for identifying halo nuclei.

One- and two-quasiparticle spectra are calculated in superheavy nuclei ${}^{293}119$ and ${}^{294,296,298}119$, respectively, within the two-center shell model. Possible $\alpha$-decay chains of those 119 nuclei are analyzed. The role of isomeric states in the $\alpha$-decay spectra is considered. The calculated $Q_{\alpha }$ energies are compared with available experimental data.

Weak Gamow-Teller (GT) responses for low-lying states in ${}^{71}\mathrm{Ga}$ are crucial for studying low-energy solar neutrinos and the Ga anomaly, i.e., the possible transition to the sterile state. The structures for the ground state, the first excited state, and the second excited state are evaluated for the first time using the experimental electron capture rates, the experimental charge exchange reaction (CER) rates corrected for the tensor-interaction effect, and the theoretical interacting shell model (ISM) calculations. On the basis of these experimental and theoretical results, the neutrino responses for them are evaluated. The contributions from the two excited states to the solar and ${}^{51}\mathrm{Cr}$ neutrinos are found to be $4.2\pm 1.2\%$ of that for the ground state. This is slightly larger than the ISM values but a little smaller than the CER values without corrections for the tensor interaction effect. The Ga anomaly is far beyond the uncertainty of the obtained nuclear responses. The present work shows for the first time the way to evaluate the tensor contributions on the basis of the EC/$\beta$ and CER experiments and the ISM calculations.

The relativistic Hartree-Fock-Bogoliubov (RHFB) framework has been extended to incorporate axially symmetric octupole deformation, leading to the development of the O-RHFB model. This model is applied to analyze the onset of octupole deformation in ${}^{228}\mathrm{Th}$ and the proton-drip-line candidate ${}^{114}\mathrm{Ba}$ using the RHF Lagrangian PKA1 and the relativistic mean field (RMF) parameter set DD-ME2. Both interactions successfully reproduce stable octupole and quadruple deformations in the ground state of ${}^{228}\mathrm{Th}$. For ${}^{114}\mathrm{Ba}$, however, PKA1 yields a relatively soft octupole deformation, in contrast to the stable one predicted by DD-ME2. From the perspective of pseudospin symmetry (PSS), it is shown that the direct development of octupole deformation from a spherical configuration is unfavorable in both nuclei, and its onset is inevitably accompanied by significant quadruple deformation. Further analysis of PSS restoration in spherical configurations reveals a notable model discrepancy rooted in the description of nuclear binding. In particular, the exchange degrees of freedom associated with the $\pi$-pseudovactor and $\rho$-tensor couplings in PKA1 are found to play an essential role in determining nuclear binding and, consequently, in shaping the octupole-deformed characteristics of both ${}^{228}\mathrm{Th}$ and ${}^{114}\mathrm{Ba}$.

A recurring question in continuum-discretized coupled-channels calculations is which continuum channels carry the breakup coupling, both to interpret the reaction and to decide which channels a model space can safely omit. The standard answer is bin deletion: remove a channel, re-solve the coupled equations, and read the change in the elastic $S$ matrix. We show that this cannot isolate an individual channel's contribution. Deleting a channel forces the surviving model space to reorganize, with the neighboring bins rerouting through the off-diagonal Green's function, so the recorded change mixes the channel's own effect with the readjustment of all the others. Working instead from the channel-resolved Feshbach dynamic polarization potential (DPP), whose full-coupling Green's function is a fixed reference shared by every channel, we define an exclusion that removes one channel while holding that reference fixed, returning its contribution to the intact system. The two operations disagree on which continuum bins matter most, for $d+{}^{58}\mathrm{Ni}$ at 21.6 MeV even sending the intrinsically leading bin to last place under deletion. The DPP further separates each channel's action into a direct path, virtual excitation and return, and a bridge path, relayed through neighboring bins, a split deletion cannot make; it shows the bins act on the elastic channel mainly as bridges, robustly across angular momentum, and that it is this bridge coupling that reorganizes under deletion. A deletion-based channel importance is therefore best read as the truncated calculation's sensitivity to a channel's removal, not as the channel's intrinsic coupling strength.

Heavy-ion collisions produce final states with thousands to tens of thousands of particles, making their simulation among the most computationally intensive tasks in high-energy nuclear physics. We present a fast, high-fidelity generative model for heavy-ion events based on a score-driven diffusion process and the point-edge transformer architecture within the OmniLearn framework. A two-stage training strategy is performed: Stage 1 trains on lower-multiplicity O-O collisions, allowing the model to learn a stable event-and-particles representation; this is followed in Stage 2 by fine tuning on challenging high-multiplicity Pb-Pb collisions. We benchmark the generator with a broad set of closure checks, including agreement of event- and particle-level observables in one and two dimensions, flow consistency reconstructed from the generated particles, end-to-end jet finding with FastJet including key jet and substructure observables, and a classifier-based application to quantify the sample fidelity. The results are promising, showing that a compact generative model can produce realistic, high-multiplicity heavy-ion events, at a level that makes local-scale generation for heavy-ion collisions at high energies a practical goal.

The Nab (Neutron a b) experiment is designed to measure the beta-antineutrino angular correlation in free neutron $\beta$ decay with an ultimate precision goal of 0.1%, providing input for tests of Cabibbo-Kobayashi-Maskawa matrix unitarity. This measurement is performed via detection of electrons and protons in delayed coincidence using custom large-area segmented silicon detectors. We present the characterization of one such detector system to establish the proton energy and timing response, using a dedicated proton accelerator. The detected proton peak was studied for 25, 30, and 35 keV incident protons on a set of detector segments and multiple cooling cycles over a one-year period. Ionization losses were consistent with models of the detector dead layer with thicknesses less than 100 nm. The detected proton peak was stable within the uncertainty from energy calibration (0.25 keV). The rise times of detector pulses from ${}^{109}\mathrm{Cd}$ and ${}^{113}\mathrm{Sn}$ conversion electron sources were used to extract the impurity density profile and establish a precise model for the detector timing response. The observed impurity density profile varied from $(2\pm 2)\times {10}^9/{\mathrm{cm}}^3$ at the center to $(26\pm 2)\times {10}^9/{\mathrm{cm}}^3$ at the edge. This impurity density profile was then used to characterize systematic effects in proton time-of-flight measurements due to detector pulse-shape effects; the resultant proton timing systematic uncertainties were below 0.3 ns, which is sufficient for the Nab experiment.