In this work we study ordinary muon capture (OMC) on ${}^{24}\mathrm{Mg}$ from a first-principles perspective. Starting from a particular two- and three-nucleon interaction derived from chiral effective field theory, we use the valence-space in-medium similarity renormalization group (VS-IMSRG) framework to construct effective Hamiltonians and muon-capture operators, which nonperturbatively account for many-body physics outside the valence space. The obtained nuclear matrix elements are compared against those from the phenomenological shell model. The impact of including the correlations from the nuclear shell model (NSM) as well as including the induced two-body part is studied in detail. Furthermore, the effects of realistic bound-muon wave function on the operators is studied. Finally, predictions for capture rates to the lowest excited states in ${}^{24}\mathrm{Na}$ are given and compared with available data. It is found that the spectroscopic properties of ${}^{24}\mathrm{Mg}$ and its OMC daughter ${}^{24}\mathrm{Na}$ are fairly well described by both the NSM and VS-IMSRG, and that the effect of the hadronic two-body currents significantly reduces the OMC rates. Both models have some difficulties in matching the measured OMC rates, especially for the $2^{+}$ final states. This calls for further studies in other light nuclei with available OMC data.

Background: The Xe isotopic chain with four valence protons above the $Z=50$ shell closure is an ideal laboratory for the study of the evolution of nuclear deformation. At the $N=82$ shell closure, ${}^{136}\mathrm{Xe}$ presents all characteristics of a doubly closed shell nucleus with a spherical shape. In the very neutron-deficient isotopes close to $N=50$, the $\alpha$-decay chain of Xe was investigated to probe the radioactive decay properties near the drip-line and the magicity of ${}^{100}\mathrm{Sn}$. Additionally, the Xe isotopes present higher order symmetries in the nuclear deformation such as the octupole degree of freedom near $N=60$ and $N=90$ or O(6) symmetry in stable isotopes.

Purpose: The relevance of the O(6) symmetry has been investigated by measuring the spectroscopic quadrupole moment of the first excited states in ${}^{124}\mathrm{Xe}$. In the O(6) symmetry limit, the spectroscopic quadrupole moment of collective states is expected to be null.

Method: A stable ${}^{124}\mathrm{Xe}$ beam with energies of $4.03A$ MeV and $4.11A$ MeV was used to bombard a ${}^{\mathrm{nat}}\mathrm{W}$ target at the GANIL facility. Excited states were populated via the safe Coulomb excitation reaction. The collision of the heavy ions with a large $Z$ at low energy make this reaction sensitive to the diagonal $E2$ matrix element of the excited states. The recoils were detected in the $\mathrm{VAMOS}++$ magnetic spectrometer and the $\gamma$ rays in the AGATA tracking array. The least squares fitting code gosia was used for the analysis to extract both $E2$ and $M1$ transitional and $E2$ diagonal matrix elements.

Results: The rotational ground state band was populated up to the $8_1^{+}$ state as well as the $2_2^{+}$ and $4_2^{+}$ states. Using high precision spectroscopic data to constrain the gosia fit, the spectroscopic quadrupole moments of the $2_1^{+}$, $4_1^{+}$, and $6_1^{+}$ states were determined for the first time.

Conclusions: The spectroscopic quadrupole moments were found to be negative, large, and constant in the ground state band underlining the prolate axially deformed ground state band of ${}^{124}\mathrm{Xe}$. The present experimental data confirm that the O(6) symmetry is substantially broken in ${}^{124}\mathrm{Xe}$.

The $\beta$-decay half-lives of four semimagic and magic nuclei, ${}^{34}\mathrm{Si}, {}^{68,78}\mathrm{Ni}$, and ${}^{132}\mathrm{Sn}$, have been investigated using the self-consistent Hartree-Fock (HF) plus subtracted second random-phase approximation (SSRPA) model with Skyrme energy density functions (EDFs). The inclusion of the two-particle–two-hole (2p-2h) configurations in SSRPA model shifts low-lying Gamow-Teller (GT) states downward. It leads to an increase of the $\beta$-decay phase space, which ensures the half-lives of the four nuclei are finite and reduces the $\beta$-decay half-lives dramatically. The effect of tensor interaction on the $\beta$-decay half-life in the SSRPA model is to change the half-lives greatly by about one to two orders of magnitude with respect to the ones obtained without tensor force.

Detailed assessments of the ability of recent theoretical approaches to modeling existing experimental data for ternary fission confirm earlier indications that the dominant mode of cluster formation in ternary fission is clusterization in very neutron-rich, very low-density, essentially chemically equilibrated nucleonic matter. An extended study and comparison of these approaches applied to ternary fission yields in the thermal neutron induced reaction ${}^{241}\mathrm{Pu}(n_{\mathrm{th}},\mathrm{f})$ has been undertaken to refine the characterization of the source matter. The resonance-gas approximation has been improved taking in-medium effects on the binding energies into account. A temperature of 1.29 MeV, density of $6.7\times {10}^{-5}\mathrm{nucleons}/{\mathrm{fm}}^3$ and proton fraction $Y_p=0.035$ are found to provide a good representation of yields of the ternary emitted light particles and clusters. In particular, results for $Z=1$ and 2 isotopes are presented. Isotopes with larger $Z$ are discussed, and the roles of medium and continuum effects, even at very low density, are illustrated.

We measured multinucleon transfer reactions for the ${}^{206}\mathrm{Pb}+{}^{118}\mathrm{Sn}$ system at $E_{\mathrm{lab}}=1200$ MeV by employing the large solid angle magnetic spectrometer PRISMA. Differential and total cross sections and $Q$-value distributions have been obtained for a variety of neutron and proton pick-up and stripping channels. The $Q$-value distributions show how the quasielastic and deep inelastic processes depend on the mass and charge of the transfer products. The corresponding cross sections have been compared with calculations performed with the grazing code. An overall good agreement is found for most of the few nucleon transfer channels. The underestimation of the data for channels involving a large number of transferred nucleons indicates that more complicated processes populate the given isotopes.

Nuclear reactions with intermediate-energy beams in which three, four, and five nucleons are removed are expected to proceed through a combination of nondissipative and statistical processes. In an experiment at the National Superconducting Cyclotron Laboratory, in-beam $\gamma$-ray spectroscopy was utilized to study few-nucleon removal reactions from incoming beams of ${}^{24}\mathrm{Mg}, {}^{25}\mathrm{Al}$, and ${}^{26}\mathrm{Si}$ projectiles to the same reaction product, ${}^{21}\mathrm{Mg}$. New $\gamma$-ray transitions and $\gamma \text{−}\gamma$ coincidences in ${}^{21}\mathrm{Mg}$ were established using the CsI(Na) array CAESAR and the inclusive cross section for three-neutron removal from ${}^{24}\mathrm{Mg}$ was measured. Significant differences in the relative population of states in ${}^{21}\mathrm{Mg}$ from ${}^{25}\mathrm{Al}$ compared to ${}^{26}\mathrm{Si}$ were observed and found to be correlated with the spins of the ${}^{21}\mathrm{Mg}$ states. As a result, this intermediate regime between direct and statistical nucleon removal may have potential as a tool to deliver unique patterns of level populations in fast-beam experiments and alter isomer to ground state ratios in the production of exotic beams.

“Ultralow” $Q$-value $\beta$ decays are referred to as such due to their low decay energies of less than $\approx 1$ keV. Such a low energy decay is possible when the parent nucleus decays to an excited state in the daughter, with an energy close to that of the $Q$ value. These decays are of interest as potential new candidates for neutrino mass determination experiments and as a testing ground for studies of atomic interference effects in the nuclear decay process. In this paper, we provide an updated evaluation of atomic mass data and nuclear energy-level data to identify potential ultralow $Q$-value $\beta$-decay candidates. For many of these candidates, more precise and accurate atomic mass data is needed to determine if the $Q$ value of the potential ultralow decay branch is energetically allowed and in fact ultralow. The relevant precise atomic mass measurements can be achieved via Penning trap mass spectrometry.

The lifetime of the $11/2_1^{+}$ state in the ${}^{131}\mathrm{Sb}$ nucleus was measured at the LOHENGRIN spectrometer of the Institut Laue-Langevin via neutron-induced fission of ${}^{235}\mathrm{U}$ using $\gamma$-ray fast-timing techniques. The obtained value of $T_{1/2}=3$(2) ps, at the edge of the sensitivity of the experimental method, is the first result for the $11/2_1^{+}$ state half-life in neutron-rich Sb isotopes. The corresponding quadrupole reduced transition probability to the ground state is $B\left(E2\right)=1.4_{-0.6}^{+1.5}$W.u., indicating a noncollective nature of this state. Realistic shell-model calculations performed in a large valence space reproduce well the experimental value and point to a dominant $2^{+}\left({}^{130}\mathrm{Sn}\right)\otimes \pi {\mathrm{g}}_{7/2}$ configuration for the $11/2_1^{+}$ state, as expected in a weak-coupling scenario. At the same time, the sum of the quadrupole strength of the multiplet states is predicted to exceed the one of the ${}^{130}\mathrm{Sn}$ core as a consequence of the equal contribution of the proton and the proton-neutron quadrupole matrix elements, pointing to possible development of collectivity already in the close neighborhood of ${}^{132}\mathrm{Sn}$.

We quantify the posterior predictive distributions (PPDs) of elastic neutron-deuteron ($nd$) scattering cross sections using nucleon-nucleon ($NN$) interactions from chiral effective field theory ($\chi \mathrm{EFT}$) up to and including next-to-next-to-next-to-leading order ($\mathrm{N}{}^3\mathrm{LO}$). These PPDs quantify the spread in $nd$ predictions due to the variability of the low-energy constants (LECs) inferred from $NN$ scattering data. We use the wave-packet continuum discretization method to solve the Alt-Grassberger-Sandhas form of the Faddeev equations for elastic scattering. We draw 100 samples from the PPDs of $nd$ cross sections up to 67 MeV in scattering energy, i.e., in the energy region where the effects of three-nucleon forces are expected to be small. We find that the uncertainty about $NN$ LECs inferred from $NN$ scattering data, when assuming uncorrelated errors, does not translate to significant uncertainty in the low-energy $nd$ continuum. Based on our estimates, the uncertainty of $nd$ predictions are dominated by the $\chi \mathrm{EFT}$ truncation error, at least below $\mathrm{N}{}^3\mathrm{LO}$. At this order, the 90% credible interval of the PPD and the truncation error are comparable, although both are very small on an absolute scale.

The excitation spectra above the breakup threshold of ${}^{11}\mathrm{C}$ were measured using the invariant mass method with a 25.0-MeV/nucleon beam bombarding a carbon target for the first time. This measurement was performed with a zero-degree double-sided silicon strip detector together with four CsI(Tl) detectors, which could detect breakup fragments with low relative kinetic energy. Some resonances in ${}^{11}\mathrm{C}$ were clearly observed in the excitation energy range of 8–14 MeV proceeding through the ${}^7\mathrm{Be}$ $+$ $\alpha$ channel. Among them, a resonance with the largest yield was observed around 8.10 MeV. We assign it as the head of the $K^{\pi }=3/2^{-}$ rotational band, and suggest the 9.38-MeV state as the second member of this band.

The Majorana Demonstrator is a leading experiment searching for neutrinoless double-beta decay with high purity germanium (HPGe) detectors. Machine learning provides a new way to maximize the amount of information provided by these detectors, but the data-driven nature makes it less interpretable compared to traditional analysis. An interpretability study reveals the machine's decision-making logic, allowing us to learn from the machine to feed back to the traditional analysis. In this work, we present the first machine learning analysis of the data from the Majorana Demonstrator; this is also the first interpretable machine learning analysis of any germanium detector experiment. Two gradient boosted decision tree models are trained to learn from the data, and a game-theory-based model interpretability study is conducted to understand the origin of the classification power. By learning from data, this analysis recognizes the correlations among reconstruction parameters to further enhance the background rejection performance. By learning from the machine, this analysis reveals the importance of new background categories to reciprocally benefit the standard Majorana analysis. This model is highly compatible with next-generation germanium detector experiments like LEGEND since it can be simultaneously trained on a large number of detectors.

Two actinide isotopes, ${}^{241}\mathrm{Am}$ and ${}^{244}\mathrm{Cm}$, produced and chemically purified by the HFIR/REDC complex at ORNL are candidates for target materials of heavy-ion fusion reaction experiments for the synthesis of new superheavy elements (SHEs) with $Z>118$. In the framework of the dinuclear system model with a dynamical potential energy surface (DNS-DyPES model), we systematically study the ${}^{48}\mathrm{Ca}$-induced reactions that have been applied to synthesize SHEs with $Z=112$–118, as well as the hot-fusion reactions with ${}^{241}\mathrm{Am}$ and ${}^{244}\mathrm{Cm}$ as targets, which are promising for synthesizing new SHEs with $Z=119$–122. Detailed results including the maximal evaporation residue cross section and the optimal incident energy for each reaction are presented and discussed.

We calculate the $E1$ breakup of the $2n$ halo nucleus ${}^{11}\mathrm{Li}$ in halo effective field theory (Halo EFT) at leading order. In Halo EFT, ${}^{11}\mathrm{Li}$ is treated as a three-body system of a ${}^9\mathrm{Li}$ core and two neutrons. We present a detailed investigation of final-state interactions (FSIs) in the neutron-neutron $\left(nn\right)$ and neutron-core $\left(nc\right)$ channels. We employ Møller operators to formulate an expansion scheme that satisfies the non-energy-weighted cluster sum rule and successively includes higher-order terms in the multiple-scattering series for the FSI. Computing the $E1$ strength up to third order in this scheme, we observe apparent convergence and good agreement with experiment. The neutron-neutron FSI is by far the most important contribution and largely determines the maximum value of the $E1$ distribution. However, inclusion of $nc$ FSI does shift the peak position to slightly lower energies. Moreover, we investigate the sensitivity of the $E1$ response to the spin structure of the neutron-${}^9\mathrm{Li}$ interaction. We contrast results for an interaction that is the same in the spin-1 and spin-2 channels with one that is only operative in the spin-2 channel, and find that good agreement with experimental data is only obtained if the interaction is present in both spin channels. The latter case is shown to be equivalent to a calculation in which the spin of ${}^9\mathrm{Li}$ is neglected.

We present a detailed study of the kinematical and dynamical conditions necessary for probing highly elusive three-nucleon short-range correlations (3N-SRCs) in nuclei through inclusive electron scattering. The kinematic requirements that should be satisfied in order to isolate 3N-SRCs in inclusive processes are derived. We demonstrate that a sequence of two short-range NN interactions is the main mechanism for 3N-SRCs in such processes. With this mechanism we predict a quadratic dependence of the cross section ratios of nuclei to ${}^3\mathrm{He}$ in the 3N-SRC region to the same ratio measured in the 2N-SRC domain. An extended analysis of the available data which satisfies the required 3N-SRC kinematical conditions is presented. This analysis reveals tantalizing signatures of the scaling associated with the onset of 3N-SRC dominance. The same data are also consistent with the prediction of the quadratic relation between the ratios measured in the 3N- and 2N-SRC regions for nuclei ranging $4\le A\le 197$. This agreement made it possible to extract $a_3\left(A\right)$, the probability of 3N-SRCs relative to the $A=3$ nucleus. We find $a_3\left(A\right)$ to be significantly larger in magnitude than the analogous parameter, $a_2\left(A\right)$, for 2N-SRCs.

The dynamics of neutron-rich light-mass compound nuclei ${}^{24,25,26,27}\mathrm{Mg}^{*}$ formed in ${}^{12,13,14,15}\mathrm{C}+{}^{12}\mathrm{C}$ fusion reactions, respectively, is explored at different $E_{\mathrm{c}.\mathrm{m}.}$ values within the dynamical cluster decay model (DCM). DCM is based on the quantum mechanical fragmentation theory, which treats the binary fragmentation of emitting compound nucleus as light particles (LPs), intermediate mass fragments (IMFs), as well as symmetric mass fragments (SMFs), on equal footing, which is not the case with other fission and statistical models. All calculations are made for spherical considerations and angular momenta taken up to the $\ell$-critical value for the respective reactions. A fusion enhancement is observed as we go from compound nuclei (CN) having an even number of neutrons (${}^{24,26}\mathrm{Mg}^{*}$) to CN with the odd number of neutrons (${}^{25,27}\mathrm{Mg}^{*}$). Interestingly, we find that the only parameter of the DCM, the neck-length parameter $\mathrm{\Delta }R$ related to the barrier lowering, is in linear relation with ${\sigma }_{\mathrm{Fusion}}$ at chosen incident laboratory energy. The fusion enhancement is found to be larger for odd neutron number nuclei, which indicates the influence of unpaired neutrons on fusion cross sections. Within the formalism of DCM, the phenomenon of fusion enhancement finds its base in the process of collective clusterization, which is quite evident from the larger values of summed-up preformation probability for the reactions having odd mass projectiles or forming odd mass CN. The DCM calculated fusion cross sections are in good agreement with the available experimental data for the given reactions.

The dynamics of the charge equilibration (CE) and the effects on the production of the neutron-rich isotopes around $N=126$ in multinucleon transfer reactions are still not well understood. In this work, we investigate the mechanism of the CE from different viewpoints by using the extended version of the dinuclear system model (DNS-sysu) and the improved quantum molecular dynamics (ImQMD) model. From the macroscopic and microscopic dynamical viewpoints, we find incomplete CE for the mass asymmetry reaction systems even in very deep collisions, and the behavior of “inverse CE” that the tendency of the fragments is away from the $N/Z$ value of the compound system in the reaction ${}^{140}\mathrm{Xe}+{}^{198}\mathrm{Pt}$. Unlike the slow process presented in the ImQMD model, the behavior of fast equilibration with the characteristic time $\approx 0.52$ zs is obtained based on the DNS-sysu model, which is consistent with the experimental data. By performing a systematic calculation, the correlation between the CE and the mass asymmetry of the reaction systems is clarified, which not only accounts for the observed intriguing phenomena of the CE but also sheds light on the optimal combinations for producing the neutron-rich isotopes around $N=126$.

We perform an extensive study of the correlations between the neutrino-nucleon inverse mean free paths (IMFPs) and the underlying equation of states (EoSs). Strong interaction uncertainties in the neutrino mean free path are investigated in different density regimes. The nucleon effective mass, the nucleon chemical potentials, and the residual interactions in the medium play an important role in determining neutrino-nucleon interactions in a density-dependent manner. We study how the above quantities are constrained by an EoS consistent with (i) nuclear mass measurements, (ii) proton-proton scattering phase shifts, and (iii) neutron star observations. We then study the uncertainties of both the charged current and the neutral current neutrino-nucleon inverse mean free paths due to the variation of these quantities, using the $\text{Hartree-Fock}+\text{random}$ phase approximation method. Finally, we calculate the Pearson correlation coefficients between (i) the EoS-based quantities and the EoS-based quantities; (ii) the EoS-based quantities and the IMFPs; (iii) the IMFPs and the IMFPs. We find a strong impact of residual interactions on neutrino opacity in the spin and spin-isospin channels, which are not well constrained by current nuclear modelings.