We analyze a recent study of the one-proton knockout reaction on ${}^{19}\mathrm{N}$ in the framework of a time-dependent two-level model. Focusing on the specific case of ${}^{18}\mathrm{C}$, we quantify the validity of the so-called “piston” mechanism in terms of the timescales involved in the process, namely, the reaction time, the period of oscillation between the mixed states, and the lifetime of the excited unbound state.

The spectroscopic quadrupole moment of the first excited $2_1^{+}$ state, $Q_S\left(2_1^{+}\right)$, at 1.970 MeV in ${}^{36}\mathrm{Ar}$ was determined at energies well below the Coulomb barrier—where nuclear interference effects are negligible—using the ${}^{194}\mathrm{Pt}({}^{36}\mathrm{Ar},{}^{36}\mathrm{Ar}^{*}){}^{194}\mathrm{Pt}^{*}$ Coulomb-excitation reaction at 134.2 MeV. Particle-gamma coincidence data were collected using the AFRODITE array—composed of eight high-purity germanium clover detectors—and an upstream double-sided silicon detector at iThemba LABS. A large diagonal matrix element of $\langle 2_1^{+}\parallel \widehat{E2}\parallel 2_1^{+}\rangle =0.163\left(42\right)$ $e\mathrm{b}$ was determined, which yields a more accurate value of $Q_S\left(2_1^{+}\right)=+0.12\left(3\right)$ $e\mathrm{b}$ as compared with previous work, $Q_S\left(2_1^{+}\right)=+0.11\left(6\right)$ $e\mathrm{b}$, in agreement with modern beyond mean-field and large-scale shell-model calculations. This value is consistent with the ratio of electric quadrupole moments found for other $A=4n$ self-conjugate nuclei extracted from the reorientation effect and the rotor model, which are surprisingly equivalent to those observed in good rotors in the mass $A\approx 160\text{–}180$ region.

We present and discuss predictions for a cross section of bulk and single-particle properties in symmetric nuclear matter based on recent high-quality nucleon-nucleon potentials at ${\mathrm{N}}^3\mathrm{LO}$ and including all subleading three-nucleon forces. We begin with the equation of state and its saturation properties and proceed to the single-nucleon potential. We also explore short-range correlations as seen through the defect function. The various predictions which we present have a common foundation in an internally consistent ab initio approach.

Lifetimes of low-spin excited states in ${}^{102}\mathrm{Mo}$ populated in a ${}^{100}\mathrm{Mo}({}^{18}\mathrm{O},{}^{16}\mathrm{O}){}^{102}\mathrm{Mo}$ two-neutron transfer reaction were measured using the recoil-distance Doppler-shift technique at the Cologne FN Tandem accelerator. Lifetimes of the $2_1^{+}$, $4_1^{+}$, $6_1^{+}$, $0_2^{+}$, $2_{\gamma }^{+}$, $3_{\gamma }^{+}$ states and one upper limit for the lifetime of the $4_{\gamma }^{+}$ state were obtained. The energy levels and deduced electromagnetic transition probabilities are compared with those obtained within the mapped interacting boson model framework with microscopic input from Gogny mean-field calculations. With the newly obtained signatures a more detailed insight in the $\gamma$ softness and shape coexistence in ${}^{102}\mathrm{Mo}$ is possible and discussed in the context of the $Z\approx 40$ and $N\approx 60$ region. The nucleus of ${}^{102}\mathrm{Mo}$ follows the $\gamma$ soft trend of the Mo isotopes. The properties of the $0_2^{+}$ state indicate, in contrast with the microscopic predictions, shape coexistence which also occurs in other $N=60$ isotones.

The symmetry energy and its density dependence are pivotal for many nuclear physics and astrophysics applications, as they determine properties ranging from the neutron-skin thickness of nuclei to the crust thickness and the radius of neutron stars. Recently, PREX-II reported a value of $0.283\pm 0.071$ fm for the neutron-skin thickness of ${}^{208}\mathrm{Pb}$, $R_{\mathrm{skin}}^{{}^{208}\mathrm{Pb}}$, implying a symmetry-energy slope parameter $L$ of $106\pm 37$ MeV, larger than most ranges obtained from microscopic calculations and other nuclear experiments. We use a nonparametric equation of state representation based on Gaussian processes to constrain the symmetry energy $S_0$, $L$, and $R_{\mathrm{skin}}^{{}^{208}\mathrm{Pb}}$ directly from observations of neutron stars with minimal modeling assumptions. The resulting astrophysical constraints from heavy pulsar masses, LIGO/Virgo, and NICER favor smaller values of the neutron skin and $L$, as well as negative symmetry incompressibilities. Combining astrophysical data with chiral effective field theory ($\chi \mathrm{EFT}$) and PREX-II constraints yields $S_0=33.0_{-1.8}^{+2.0}$ MeV, $L={53}_{-15}^{+14}$ MeV, and $R_{\mathrm{skin}}^{{}^{208}\mathrm{Pb}}=0.{17}_{-0.04}^{+0.04}$ fm. We also examine the consistency of several individual $\chi \mathrm{EFT}$ calculations with astrophysical observations and terrestrial experiments. We find that there is only mild tension between $\chi \mathrm{EFT}$, astrophysical data, and PREX-II's $R_{\mathrm{skin}}^{{}^{208}\mathrm{Pb}}$ measurement ($p$ value $=12.3\%$) and that there is excellent agreement between $\chi \mathrm{EFT}$, astrophysical data, and other nuclear experiments.

We construct an effective shell-model interaction for the valence space spanned by single-particle neutron and single-hole proton states in ${}^{100}\mathrm{Sn}$. Starting from chiral nucleon-nucleon and three-nucleon forces and single-reference coupled-cluster theory for ${}^{100}\mathrm{Sn}$ we apply a second similarity transformation that decouples the valence space. The particle-particle components of the resulting effective interaction can be used in shell model calculations for neutron deficient tin isotopes. The hole-hole interaction can be used to calculate the $N=50$ isotones south of ${}^{100}\mathrm{Sn}$, and the full particle-hole interaction describes nuclei in the region southeast of ${}^{100}\mathrm{Sn}$. We compute low-lying excited states in selected nuclei southeast of ${}^{100}\mathrm{Sn}$, and find reasonable agreement with data. The presented techniques can also be applied to construct effective shell-model interactions for other regions of the nuclear chart.

We extend an effective field theory developed to describe rotational bands in even-even nuclei to the odd-mass case. This organizes Bohr and Mottelson's treatment of a particle coupled to a rotor as a model-independent expansion in powers of the angular velocity of the overall system. We carry out this expansion up to fourth order in the angular velocity and present results for ${}^{99}\mathrm{Tc}$, ${}^{159}\mathrm{Dy}$, ${}^{167,169}\mathrm{Er}$, ${}^{167,169}\mathrm{Tm}$, ${}^{183}\mathrm{W}$, ${}^{235}\mathrm{U},$ and ${}^{239}\mathrm{Pu}$. In each case, the accuracy and breakdown scale of the effective field theory can be understood based on the single-particle and vibrational energy scales in that nucleus.

It is often stated that heavy-ion nucleon knockout reactions are mostly sensitive to the tails of the bound-state wave functions. In contrast, $(p,2p)$ and $(p,pn)$ reactions are known to access information on the full overlap functions within the nucleus. We analyze the oxygen isotopic chain and explore the differences between single-particle wave functions generated with potential models, used in the experimental analysis of knockout reactions, and ab initio computations from self-consistent Green's function theory. Contrary to common belief, we find that not only the tail of the overlap functions, but also their internal part is assessed in both reaction mechanisms, which are crucial to yield accurately determined spectroscopic information.

Large scheme shell-model calculations are conducted for the two-neutrino double-$\beta$ $\left(2\nu \beta \beta \right)$ decay of the $fp$ $(0f_{7/2},0f_{5/2},1p_{3/2},1p_{1/2})$ shell nuclei. 25 $2\nu \beta \beta$ processes are considered, of which seven $2\nu \beta \beta$ processes are either observed or candidates. The calculated half-lives, nuclear matrix elements (NMEs), strength function (SF) distributions, and phase space factors are shown. The calculated results agree with the experimental data and reveal that for the transitions involving a doubly, semimagic nucleus or only the nonmagic nuclei, the SF distributions are visibly different. This outcome indicates that the NMEs of the $2\nu \beta \beta$ processes are significantly influenced by the closed-shell effect.

Besides the direct comparison with the experimental mass values, the $\alpha$ decay energy $\left(Q_{\alpha }\right)$, as one type of the mass difference, can be considered as another factor to judge the accuracy and validity of modern nuclear mass models. In the present study, the Duflo-Zuker (DZ) mass model is employed to match the measured $Q_{\alpha }$ value besides the mass data. This procedure can not only provide us a new way to evaluate and predict the $\alpha$ decay energy, but also raise one more constraint on the theoretical mass scheme. It is found that all the experimental $\alpha$ decay energies, from the ground state (g.s.) to g.s. transition of even-even nuclei above $A=100$, can be well reproduced in a quite improved accuracy. Moreover, the symmetry term, involved in the macroscopic part of the DZ model, is refined further to regulate the behavior of the ambiguous symmetry energy coefficient in the nuclear equation of state. Through the relationship between the slope parameter of the symmetry energy and the neutron skin thickness, the neutron thickness $\mathrm{\Delta }{R}_{np}$ of ${}^{208}\mathrm{Pb}$ is determined in the vicinity of 0.201 fm, which is compatible to the very recent measurement.

Excited levels in ${}^{90}\mathrm{Sr}$, ${}^{92}\mathrm{Sr}$, ${}^{94}\mathrm{Sr}$, and ${}^{96}\mathrm{Sr}$ nuclei were reinvestigated using high-statistics multiple-$\gamma$ coincidence data from neutron-induced fission of ${}^{235}\mathrm{U}$ and spontaneous fission of ${}^{252}\mathrm{Cf}$, measured using Exogam at Institut Laue Langevin and Gammasphere arrays, respectively. The experimental goal was the search for new excited levels and firm spin-parity assignments to known levels. A total of 23 new levels with 30 new or corrected decays and 39 new or improved spin-parity assignments were obtained in the four nuclei. Negative-parity structures on top of $3^{-}$ excitation were firmly identified and extended to higher spins. New positive-parity structures in ${}^{94}\mathrm{Sr}$ and ${}^{96}\mathrm{Sr}$ were observed with $3^{+}$ excitations characteristic of $\gamma$ collectivity. The 277.7-keV, $E2$ decay from the 1507.0-keV level to the second $0^{+}$ level in ${}^{96}\mathrm{Sr}$, found in this paper, completes the coexisting deformed band in this nucleus. To learn about the microscopic structure of levels in the ${}^{88-96}\mathrm{Sr}$ nuclei, we performed large-scale shell-model calculations. The calculations compared to the experiment, helped the discussion of the evolution of collectivity in strontium isotopes, highlighting the important role of various single-particle excitations in phase transitions and shape coexistence in the region. The special role of the neutron $9/2^{+}\left[404\right]$ extruder as a catalyst of the deformation change in the region is highlighted.

Background: Modern statistical tools provide the ability to compare the information content of observables and provide a path to explore which experiments would be most useful to give insight into and constrain theoretical models.

Purpose: In this work we study three such tools in the context of nuclear reactions with the goal of constraining the optical potential.

Method: The three statistical tools examined are (i) the principal component analysis, (ii) the sensitivity analysis based on derivatives, and (iii) the Bayesian evidence. We first apply these tools to a toy-model case, comparing the form of the imaginary part of the optical potential. Then we consider two different reaction observables, elastic angular distributions and polarization data for reactions on ${}^{48}\mathrm{Ca}$ and ${}^{208}\mathrm{Pb}$ at two different beam energies.

Results: For the toy-model case, we find significant discrimination power in the sensitivities and the Bayesian evidence, showing clearly that the volume imaginary term is more useful to describe scattering at higher energies. When comparing between elastic cross sections and polarization data using realistic optical models, sensitivity studies indicate that both observables are roughly equally sensitive but the variability of the optical model parameters is strongly angle dependent. The Bayesian evidence shows some variability between the two observables, but the Bayes factor obtained is not sufficient to discriminate between angular distributions and polarization.

Conclusions: From the cases considered, we conclude that, in general, elastic scattering angular distributions have similar impact in constraining the optical potential parameters compared with the polarization data. The angular ranges for the optimum experimental constraints can vary significantly with the observable considered.

I present a new formalism of the $R$-matrix theory where the formal parameters for the resonance energies and widths are identical to the observed values. By allowing the boundary condition parameters to vary from level to level, the freedom required to adjust the formal parameters for the pole positions to the observed values is obtained. The basis of the resulting theory becomes nonorthogonal, and I describe the procedure to construct a consistent $R$-matrix theory with such a nonorthogonal basis. And by adjusting the normalization of the states that form the basis, the formal parameters for the reduced decay widths also become the same as those observed, leaving no formal parameters that are different from the observed ones. A demonstration of the developed theory to the elastic ${}^{12}\mathrm{C}+p$ scattering data is presented.

The data on transverse momentum integrated hadron yields in different multiplicity classes of $p+p$ collisions at $\sqrt{s}=7$ TeV have been analyzed to extract the chemical freeze-out parameters using a thermal model. The chemical freeze-out parameters have been extracted for three different freeze-out schemes: (i) unified freeze-out for all hadrons in complete thermal equilibrium (1CFO), (ii) unified freeze-out for all hadrons with an additional parameter ${\gamma }_S$ which accounts for possible out-of-equilibrium production of strange hadrons ($1\mathrm{CFO}+{\gamma }_S$), and (iii) separate freeze-out for hadrons with and without strangeness content (2CFO). It has been observed that the $1\mathrm{CFO}+{\gamma }_S$ scheme gives the best description of the hadronic yields at midrapidity when multiplicity ($\langle d{N}_{ch}/d\eta \rangle$) of the collision is less than 10. This indicates that the strangeness is out of equilibrium in most of the multiplicity classes of $p+p$ collisions. All three parameters of this CFO scheme, temperature $T$, radius $R$ of the fireball, and strangeness suppression factor ${\gamma }_S$ increase with the increase of $\langle d{N}_{ch}/d\eta \rangle$. Furthermore, we have compared applicability of different CFO schemes considering two more colliding systems $p+\text{Pb}$ at $\sqrt{s_{\mathrm{NN}}}=5.02$ and $\text{Pb}+\text{Pb}$ at $\sqrt{s_{\mathrm{NN}}}=2.76$ TeV along with $p+p$ collisions at $\sqrt{s}=7$ TeV. We observe a freeze-out volume (or multiplicity) dependence of CFO schemes regardless of colliding ions. The $1\text{CFO}+{\gamma }_S$, 1CFO, and 2CFO schemes provide the best description of the data when the dimensionless quantity $V{T}^3$ approximately satisfies the conditions $V{T}^3<50, 50<V{T}^3<100$, and $V{T}^3>100$, respectively, or the corresponding multiplicity satisfies the conditions $\langle d{N}_{ch}/d\eta \rangle <30, 30<d{N}_{ch}/d\eta <60$, and $\langle d{N}_{ch}/d\eta \rangle >100$, respectively.

We utilize an isobar model to investigate the $K^{+}{\mathrm{\Sigma }}^{-}$ photoproduction off a neutron in the resonance region. Except for the Born terms, we include high-spin (spin-3/2 and spin-5/2) nucleon resonances in the consistent formalism together with a few $\mathrm{\Delta }$ and kaon resonances to achieve an acceptable agreement with data. Interestingly, we reveal that no hyperon resonances are needed to achieve a reasonable description of data. On the other hand the $N\left(1720\right)3/2^{+}$ resonance was found to be very important for correct description of data. The free parameters of the model were fitted to experimental data from the LEPS and CLAS Collaborations on either differential cross sections or photon beam asymmetry. The novel feature of the fitting procedure is the use of a regularization method, the least absolute shrinkage selection operator, and information criteria in order to choose the best fit.

We report precision mass measurements of neutron-deficient gallium isotopes approaching the proton drip line. The measurements of ${}^{60\text{–}63}\mathrm{Ga}$ performed with the TITAN multiple-reflection time-of-flight mass spectrometer provide a more than threefold improvement over the current literature mass uncertainty of ${}^{61}\mathrm{Ga}$ and mark the first direct mass measurement of ${}^{60}\mathrm{Ga}$. The improved precision of the ${}^{61}\mathrm{Ga}$ mass has important implications for the astrophysical $rp$ process, as it constrains essential reaction $Q$ values near the ${}^{60}\mathrm{Zn}$ waiting point. Based on calculations with a one-zone model, we demonstrate the impact of the improved mass data on prediction uncertainties of x-ray burst models. The first-time measurement of the ${}^{60}\mathrm{Ga}$ ground-state mass establishes the proton-bound nature of this nuclide, thus constraining the location of the proton drip line along this isotopic chain. Including the measured mass of ${}^{60}\mathrm{Ga}$ further enables us to extend the evaluated $T=1$ isobaric multiplet mass equation up to $A=60$.

Closed shell charmed hypernuclei ${}_{{\mathrm{\Lambda }}_c}{}^5\mathrm{Li}, {}_{{\mathrm{\Lambda }}_c}{}^{17}\mathrm{F}, {}_{{\mathrm{\Lambda }}_c}{}^{41}\mathrm{Sc}, {}_{{\mathrm{\Lambda }}_c}{}^{57}\mathrm{Cu}, {}_{{\mathrm{\Lambda }}_c}{}^{133}\mathrm{Sb}$, and ${}_{{\mathrm{\Lambda }}_c}{}^{209}\mathrm{Bi}$ are calculated within the Hartree-Fock approach by using three different force sets derived from microscopic Brueckner-Hartree-Fock calculations of $\mathrm{\Lambda }$ hypernuclei. Ground state properties (binding energies, ${\mathrm{\Lambda }}_c$ separation energies, ${\mathrm{\Lambda }}_c$ single particle energies, and ${\mathrm{\Lambda }}_c$ densities) of charmed nuclei are examined. We confirm the results and conclusions of different models from the literature, related to ${\mathrm{\Lambda }}_c$ hypernuclei. Due to the Coulomb repulsion between protons and the ${\mathrm{\Lambda }}_c$ baryon, charmed hypernuclei are most bound for $16\le A\le 41$, where ${}_{{\mathrm{\Lambda }}_c}{}^{17}\mathrm{F}$ can be considered as an excellent candidate to determine charmed hypernuclei properties. The competition between the attractive nucleon-${\mathrm{\Lambda }}_c$ interaction and the Coulomb repulsion is discussed, and we compare $\mathrm{\Lambda }$ and ${\mathrm{\Lambda }}_c$ hypernuclei properties.

Bayesian machine learning is a promising tool for the evaluation of nuclear fission data but its potential capability has not been fully realized. We attempt to optimize the performances of the multilayer Bayesian neural networks for evaluations of fission yields. The influences of adjustments of learning data, activation functions, and network structures have been studied. In particular, negative values of net functions have been penalized to avoid nonphysical inferences of fission yields. Presently the network with double hidden layers has optimal performances compared to the single-layer or deeper networks. These studies are essential for further developments of precise evaluation methods.