Baryonic matter close to the saturation density is very likely to present complex inhomogeneous structures collectively known under the name of nuclear pasta phase. At finite temperature, the different geometric structures are expected to coexist with potential consequences on the neutron star crust conductivity and neutrino transport in supernova matter. In the framework of a statistical multicomponent approach, we calculate the composition of matter in the pasta phase considering density, proton fraction, and geometry fluctuations. Using a realistic energy functional from relativistic mean-field theory and a temperature- and isospin-dependent surface tension fitted from Thomas-Fermi calculations, we show that different geometries can coexist in a large fraction of the pasta phase, down to temperatures of the order of the crystallization temperature of the neutron star crust. Quantitative estimates of the charge fluctuations are given.

The astrophysical ${}^{25}\mathrm{Al}(p,\gamma ){}^{26}\mathrm{Si}$ reaction represents one of the key remaining uncertainties in accurately modeling the abundance of radiogenic ${}^{26}\mathrm{Al}$ ejected from classical novae. Specifically, the strengths of key proton-unbound resonances in ${}^{26}\mathrm{Si}$, that govern the rate of the ${}^{25}\mathrm{Al}(p,\gamma )$ reaction under explosive astrophysical conditions, remain unsettled. Here, we present a detailed spectroscopy study of the ${}^{26}\mathrm{Si}$ mirror nucleus ${}^{26}\mathrm{Mg}$. We have measured the lifetime of the $3^{+}$, 6.125-MeV state in ${}^{26}\mathrm{Mg}$ to be $19\left(3\right)\mathrm{fs}$ and provide compelling evidence for the existence of a $1^{-}$ state in the $T=1,A=26$ system, indicating a previously unaccounted for $\ell =1$ resonance in the ${}^{25}\mathrm{Al}(p,\gamma )$ reaction. Using the presently measured lifetime, together with the assumption that the likely $1^{-}$ state corresponds to a resonance in the ${}^{25}\mathrm{Al}+p$ system at 435.7(53) keV, we find considerable differences in the ${}^{25}\mathrm{Al}(p,\gamma )$ reaction rate compared to previous works. Based on current nova models, we estimate that classical novae may be responsible for up to $\approx 15\%$ of the observed galactic abundance of ${}^{26}\mathrm{Al}$.

The gyromagnetic factor of the low-lying $E_x=684.10\left(19\right)\mathrm{keV}$ isomeric state of the nucleus ${}^{99}\mathrm{Mo}$ was measured using the time-dependent perturbed angular distribution technique. This level is assigned a spin and parity of $J^{\pi }=11/2^{-}$, with a half-life of $T_{1/2}=742\left(13\right)\mathrm{ns}$. The state of interest was populated and spin-aligned via a single-neutron transfer on a highly enriched ${}^{98}\mathrm{Mo}$ target. A magnetic moment ${\mu }_{\mathrm{expt}.}=-0.627\left(20\right){\mu }_{\mathrm{N}}$ was obtained. This result is far from the Schmidt value expected for a pure single-particle $\nu h_{11/2}$ state. A comparison of experimental spectroscopic properties of this nucleus is made with results of multishell Interacting boson-fermion Model (IBFM-1) calculations. In this approach, the $J^{\pi }=11/2^{-}$ isomeric state in ${}^{99}\mathrm{Mo}$ has a pure $\nu h_{11/2}$ configuration. Its magnetic moment, as well as that of other two excited states could be reasonably well reproduced by reducing the free neutron spin $g$ factor with a quenching factor of 0.45. This low value is not appropriate only for this case, similar values for the quenching factor being also required in order to describe magnetic moments in other nuclei from the same mass region.

Background: Investigation of the ${}_{62}{}^{140}\mathrm{Sm}_{78}$ nucleus, situated in the area close to the magic $N=82$ neutron shell, offers the opportunity to find and study interesting phenomena resulting from the interplay of collective and other degrees of freedom.

Purpose: Experimental identification of low-spin low-energy levels, particularly $0^{+}$, in ${}^{140}\mathrm{Sm}$ and theoretical interpretation within the collective general Bohr Hamiltonian (GBH) model.

Method: The $\gamma \text{−}\gamma$ angular correlation technique for $\gamma$ radiation after the $\beta$/EC decay of ${}^{140}\mathrm{Eu}\to {}^{140}\mathrm{Sm}$ and ${}^{140}\mathrm{Gd}\to {}^{140}\mathrm{Eu}\to {}^{140}\mathrm{Sm}$ was used to determine spins of excited states of ${}^{140}\mathrm{Sm}$. The ${}^{140}\mathrm{Gd}$ and ${}^{140}\mathrm{Eu}$ nuclei were produced in the ${}^{104}\mathrm{Pd}+{}^{40}\mathrm{Ar}$ reaction at the HIL UW cyclotron. In the theoretical part the full five-dimensional GBH model was applied in two variants: the simple phenomenological Warsaw model and the microscopic version with six inertial functions and a potential calculated from mean-field theory.

Results: The spin and parity of six low spin (0,1,2) low lying excited levels of ${}^{140}\mathrm{Sm}$ were measured. Two new states at around 2 MeV were identified. A analysis of the consequences of possible admixtures on the determination of the spin of a level was performed. The theoretical models applied successfully describe most of the spectrum of ${}^{140}\mathrm{Sm}$ giving hints on the origin of the states observed in the experiment.

Conclusions: Significant softness against nonaxial deformation seems to be essential to interpret the properties of ${}^{140}\mathrm{Sm}$. Further experimental studies are needed to check if some low-energy excitations are not deformation driven.

The $R$-matrix analysis of $A=5$ nuclear systems has been partially validated by applying the technique to the ${}^5\mathrm{Li}$ system and comparing the predicted $\gamma$-ray spectrum with historical data. $R$-matrix analysis of the similar ${}^5\mathrm{He}$ system was then used to predict the $\gamma$-ray spectral shape for the deuterium-tritium (DT) reaction. The resulting spectra have been used in the analysis of DT implosions on the Omega laser where the $\gamma$-ray interaction rate was measured by a gas Cherenkov detector. Comparison of predictions to experiment confirmed the presence of both 16.75 and $\approx 13$ MeV $\gamma$-ray contributions; analysis, using $R$-matrix spectra, yielded a ratio of $\gamma$-ray emission from a transition to the intermediate excited state to that from a transition to the ground state of $(2.1\pm 0.4):1$, substantiating the first spectral measurement of the DT fusion $\gamma$ ray in an inertial fusion environment.

In the standard effective $V-A$ theory of low-energy weak interactions [i.e., in the standard model (SM)] we analyze the structure of the correlation coefficients $S\left(E_e\right)$ and $U\left(E_e\right)$, where $E_e$ is the electron energy. These correlation coefficients were introduced to the electron-energy and angular distribution of the neutron beta decay by Ebel and Feldman [Nucl. Phys. 4, 213 (1957)] in addition to the set of correlation coefficients proposed by Jackson et al. [Phys. Rev. 106, 517 (1957)]. The correlation coefficients $S\left(E_e\right)$ and $U\left(E_e\right)$ are induced by simultaneous correlations of the neutron and electron spins and electron and antineutrino three-momenta. These correlation structures do no violate discrete P, C, and T symmetries. We analyze the contributions of the radiative corrections of order $O(\alpha /\pi )$, taken to leading order in the large nucleon mass $m_N$ expansion, and corrections of order $O(E_e/m_N)$, caused by weak magnetism and proton recoil. In addition to the radiative $O(\alpha /\pi )$ and $O(E_e/m_N)$ corrections we take into account the contributions of the second class currents by Weinberg [Phys. Rev. 112, 1375 (1958)]. The contributions of interactions beyond the SM (BSM) are calculated in terms of the phenomenological coupling constants of BSM interactions by Lee and Yang [Phys. Rev. 104, 254 (1956)].

The $A=4$ nuclei, i.e., ${}^4\mathrm{H}, {}^4\mathrm{He}$, and ${}^4\mathrm{Li}$, establish an interesting isospin $T=1$ isobaric system. ${}^4\mathrm{H}$ and ${}^4\mathrm{Li}$ are unbound broad resonances, whereas ${}^4\mathrm{He}$ is deeply bound in its ground state but unbound in all its excited states. The present situation is that experiments so far have not given consistent data on the resonances. Few-body calculations have well studied the scatterings of the $4N$ systems. In the present work, we provide many-body calculations of the broad resonance structures, in an ab initio framework with modern realistic interactions. It occurs that, indeed, ${}^4\mathrm{H}, {}^4\mathrm{Li}$, and excited ${}^4\mathrm{He}$ are broad resonances, which is in accordance with experimental observations. The calculations also show that the first $1^{-}$ excited state almost degenerates with the $2^{-}$ ground state in the pair of mirror isobars of ${}^4\mathrm{H}$ and ${}^4\mathrm{Li}$, which may suggest that the experimental data on energy and width are the mixture of the ground state and the first excited state. The $T=1$ isospin triplet formed with an excited state of ${}^4\mathrm{He}$ and ground states of ${}^4\mathrm{H}$ and ${}^4\mathrm{Li}$ is studied, focusing on the effect of isospin symmetry breaking.

Lifetimes are measured for low lying states of ${}^{150}\mathrm{Sm}$, populated from ${\beta }^{-}$ decay of ${}^{150}\mathrm{Pm}$ produced through $(p,n)$ reactions with a ${}^{150}\mathrm{Nd}$ target. The VENTURE array comprising of eight fast ${\mathrm{CeBr}}_3$ detectors is used for lifetime measurement with $\gamma \text{−}\gamma$ fast timing technique. The lifetime of $0_3^{+}$ level of ${}^{150}\mathrm{Sm}$ is measured for the first time to be 36(10) ps. The $0_3^{+}$ level is found to have enhanced decay strengths to the $K^{\pi }=0_2^{+}$ structure compared with $K^{\pi }=0_1^{+}$. A high ${\rho }^2\left(E0\right)$ strength for the $0_3^{+}\to 0_2^{+}$ decay confirms shape coexistence and shape mixing in $N=88{}^{150}\mathrm{Sm}$.

In the present work we study the effects of strongly quantizing magnetic fields and finite temperature on the properties of inner crusts of hot neutron stars. In particular, we study the effects of Landau quantization of electrons on the composition of the NS inner crusts. The inner crust of a neutron star contains neutron-rich nuclei arranged in a lattice and embedded in gases of free neutrons and electrons. We describe the system within the Wigner-Seitz (WS) cell approximation. The nuclear energy is calculated using Skyrme model with SkM* interaction. To isolate the properties of nuclei we follow the subtraction procedure presented by Bonche, Levit, and Vautherin [Nuc. Phys. A 427, 278 (1984); Nuc. Phys. A 436, 265 (1985)], within the Thomas-Fermi approximation. We obtain the equilibrium properties of the inner crust for various density, temperatures, and magnetic fields by minimizing the free energy of the WS cell satisfying the charge neutrality and $\beta$-equilibrium conditions. We infer that at a fixed baryon density and temperature, a strong quantizing magnetic field reduces the cell radii, neutron, and proton numbers in the cell compared with the field free case. However, the nucleon number in the nucleus increases in the presence of a magnetic field. The free energy per nucleon also decreases in the magnetized inner crust. On the other hand, we find that finite temperature tends to smear out the effects of magnetic field. Our results can be important in the context of $r$-process nucleosynthesis in the binary neutron star mergers.

Background: Rotational bands have been measured around ${}^{250}\mathrm{Fm}$ associated with strong deformed-shell closures. The $K^{\pi }=2^{-}$ excited band emerges systematically in $N=150$ isotones raging from plutonium to nobelium with even-$Z$ numbers, and a sharp drop in energies was observed in californium.

Purpose: I attempt to uncover the microscopic mechanism for the appearance of such a low-energy $2^{-}$ state in ${}^{248}\mathrm{Cf}$. Furthermore, I investigate the possible occurrence of the low-energy $K^{\pi }=2^{+}$ state, the $\gamma$ vibration, to elucidate the mechanism that prefers the simultaneous breaking of the reflection and axial symmetry to the breaking of the axial symmetry alone in this mass region.

Method: I employ a nuclear energy-density functional (EDF) method: the Skyrme-Kohn-Sham-Bogoliubov and the quasiparticle random-phase approximation are used to describe the ground state and the transition to excited states.

Results: The Skyrme-type SkM* and SLy4 functionals reproduce the fall in energy but not the absolute value of the $K^{\pi }=2^{-}$ state at $Z=98$ where the proton two-quasiparticle excitation $\left[633\right]7/2\otimes \left[521\right]3/2$ plays a decisive role for the peculiar isotonic dependence. I find interweaving roles by the pairing correlation of protons and the deformed-shell closure at $Z=98$. The SkM* model predicts the $K^{\pi }=2^{-}$ state appears lower in energy in ${}^{246}\mathrm{Cf}$ than in ${}^{248}\mathrm{Cf}$ as the Fermi level of neutrons is located in between the [622]5/2 and the [734]9/2 orbitals. Except for ${}^{250}\mathrm{Fm}$ in the SkM* calculation, the $K^{\pi }=2^{+}$ state is predicted to appear higher in energy than the $K^{\pi }=2^{-}$ state because the quasiproton [521]1/2 orbital is located above the [633]7/2 orbital.

Conclusions: A systematic study of low-lying collective states in heavy actinide nuclei provides a rigorous testing ground for microscopic nuclear models. The present paper shows a need for improvements in the EDFs to describe pairing correlations and shell structures in heavy nuclei, that are indispensable in predicting the heaviest nuclei.

In this work we have reexamined the shape isomer in ${}^{235}\mathrm{U}$. Reanalyzing data from a previous experiment gave a half-life of $T_{1/2}=(11\pm 3)\mathrm{ms}$ and a cross section for populating the isomer of ${\sigma }_{\mathrm{iso}}=(12\pm 1)\mu \mathrm{b}$. Combining these new results with measured properties of fission fragments from the reaction ${}^{234}\mathrm{U}(n,f)$ allowed extracting parameters describing the outer fission barrier. The deduced barrier parameters are $E_B=(5.7\pm 0.6)$ MeV and $\hslash {\omega }_B=(0.5\pm 0.1)$ MeV for the height and curvature, respectively, as well as the energy of the superdeformed ground state $E_{II}=(2.4\pm 0.6)$ MeV. Separate barrier parameters for the standard-1 and standard-2 fission modes have been estimated, too. Finally, the results obtained in this work have been successfully tested for their plausibility.

We report a new determination of $\widehat{q}$, the jet transport coefficient of the quark-gluon plasma. We use the JETSCAPE framework, which incorporates a novel multistage theoretical approach to in-medium jet evolution and Bayesian inference for parameter extraction. The calculations, based on the Matter and Lbt jet quenching models, are compared to experimental measurements of inclusive hadron suppression in $\mathrm{Au}+\mathrm{Au}$ collisions at the BNL Relativistic Heavy Ion Collider (RHIC) and $\mathrm{Pb}+\mathrm{Pb}$ collisions at the CERN Large Hadron Collider (LHC). The correlation of experimental systematic uncertainties is accounted for in the parameter extraction. The functional dependence of $\widehat{q}$ on jet energy or virtuality and medium temperature is based on a perturbative picture of in-medium scattering, with components reflecting the different regimes of applicability of Matter and Lbt. In the multistage approach, the switch between Matter and Lbt is governed by a virtuality scale $Q_0$. Comparison of the posterior model predictions to the RHIC and LHC hadron suppression data shows reasonable agreement, with moderate tension in limited regions of phase space. The distribution of $\widehat{q}/T^3$ extracted from the posterior distributions exhibits weak dependence on jet momentum and medium temperature $T$, with 90% credible region (CR) depending on the specific choice of model configuration. The choice of Matter$+$Lbt, with switching at virtuality $Q_0$, has 90% CR of $2<\widehat{q}/T^3<4$ for $p_{T,\mathrm{jet}}>40 \mathrm{GeV}/c$. The value of $Q_0$, determined here for the first time, is in the range 2.0–2.7 GeV.

We report on the measurement of the beam spin asymmetry in the deeply virtual Compton scattering off ${}^4\mathrm{He}$ using the CEBAF Large Acceptance Spectrometer (CLAS) at Jefferson Lab using a 6 GeV longitudinally polarized electron beam incident on a pressurized ${}^4\mathrm{He}$ gaseous target. We detail the method used to ensure the exclusivity of the measured reactions, in particular the upgrade of CLAS with a radial time projection chamber to detect the low-energy recoiling ${}^4\mathrm{He}$ nuclei and an inner calorimeter to extend the photon detection acceptance at forward angles. Our results confirm the theoretically predicted enhancement of the coherent ($e{}^4\mathrm{He}\to e^{\prime }\stackrel{\prime }{{}^4\mathrm{He}}{\gamma }^{\prime }$) beam spin asymmetries compared to those observed on the free proton, while the incoherent ($e{}^4\mathrm{He}\to e^{\prime }{p}^{\prime }{\gamma }^{\prime }{X}^{\prime }$) asymmetries exhibit a $30\%$ suppression. From the coherent data, we were able to extract, in a model-independent way, the real and imaginary parts of the only ${}^4\mathrm{He}$ Compton form factor, ${\mathcal{H}}_A$, leading the way toward 3D imaging of the partonic structure of nuclei.

In any finite system, the presence of a nonzero permanent electric dipole moment (EDM) would indicate CP violation beyond the small violation predicted in the standard model. Here, we use the ab initio no-core shell model framework to theoretically investigate the magnitude of the nuclear EDM. We calculate EDMs of several light nuclei using chiral two- and three-body interactions and a PT-violating Hamiltonian based on a one-meson-exchange model. We present a benchmark calculation for ${}^3\mathrm{He}$, as well as results for the more complex nuclei ${}^{6,7}\mathrm{Li}, {}^9\mathrm{Be}, {}^{10,11}\mathrm{B}, {}^{13}\mathrm{C}, {}^{14,15}\mathrm{N}$, and ${}^{19}\mathrm{F}$. Our results suggest that different nuclei can be used to probe different terms of the PT-violating interaction. These calculations allow us to suggest which nuclei may be good candidates in the search for a measurable permanent electric dipole moment.

Background: Shell hydrogen burning during the asymptotic giant branch (AGB) phase through the oxygen isotopes has been indicated as a key process that is needed to understand the observed ${}^{18}\mathrm{O}/{}^{16}\mathrm{O}$ relative abundance in presolar grains and in stellar atmospheres. This ratio is strongly influenced by the relative strengths of the reactions ${}^{18}\mathrm{O}(p,\alpha ){}^{15}\mathrm{N}$ and ${}^{18}\mathrm{O}(p,\gamma ){}^{19}\mathrm{F}$ in low-mass AGB stars. While the former channel has been the focus of a large number of measurements, the $(p,\gamma )$ reaction path has only recently received some attention and its stellar reaction rate over a wide temperature range rests on only one measurement.

Purpose: Our aim is the direct measurement of states in ${}^{19}\mathrm{F}$ as populated through the reaction ${}^{18}\mathrm{O}(p,\gamma ){}^{19}\mathrm{F}$ to better determine their influence on the astrophysical reaction rate, and more generally to improve the understanding of the nuclear structure of ${}^{19}\mathrm{F}$.

Method: Branchings and resonance strengths were measured in the proton energy range $E_{\mathrm{p}}^{\mathrm{lab}}=150–400\mathrm{keV}$, using a high-purity germanium detector inside a massive lead shield. The measurement took place in the ultra-low-background environment of the Laboratory for Underground Nuclear Astrophysics (LUNA) experiment at the Gran Sasso National Laboratory, leading to a highly increased sensitivity.

Results: The uncertainty of the $\gamma$ branchings and strengths was improved for all four resonances in the studied energy range; many new transitions were observed in the case of the $334\mathrm{keV}$ resonance, and individual $\gamma$ decays of the $215\mathrm{keV}$ resonance were measured for the first time. In addition a number of transitions to intermediate states that decay through $\alpha$ emission were identified. The strengths of the observed resonances are generally in agreement with literature values.

Conclusions: Our measurements substantially confirm previous determinations of the relevant resonance strengths. Therefore the ${}^{18}\mathrm{O}(p,\gamma ){}^{19}\mathrm{F}$ reaction rate does not change with respect to the reaction rate reported in the compilations commonly adopted in the extant computations of red-giant branch and AGB stellar models. Nevertheless, our measurements definitely exclude a nonstandard scenario for the fluorine nucleosynthesis and a nuclear physics solution for the ${}^{18}\mathrm{O}$ depletion observed in Group 2 oxygen-rich stardust grains.

The structure of ${}^{80}\mathrm{Ge}$ has been investigated at the ISOLDE facility at CERN. A previous study reported for the first time a low-lying $0_2^{+}$ intruder state at 639 keV, based on the coincidence with a previously unobserved 1764-keV $\gamma$ ray, and suggested it as evidence for shape coexistence in ${}^{80}\mathrm{Ge}$. We used the $\beta$ decay from the $3^{-}$ 22.4-keV state in ${}^{80}\mathrm{Ga}$ to enhance the population of low-spin states in ${}^{80}\mathrm{Ge}$, including any excited $0^{+}$ level, and $\gamma \gamma$ coincidences to investigate it. We observed a 1764-keV $\gamma$ ray in coincidence with strong transitions in ${}^{80}\mathrm{Ge}$, thus not feeding the proposed 639-keV $0_2^{+}$. No connecting transitions from previously known levels to the 639-keV and 2403-keV $2_3^{+}$ states could be established either. Shell-model calculations for Ge isotopes and $N=48$ isotones were performed. They succeed to explain most of the experimental levels, but fail to reproduce the presence of a $0_2^{+}$ state below $\approx 1200$ keV in ${}^{80}\mathrm{Ge}$. Our experimental findings and shell-model calculations are difficult to reconcile with a very low-lying $0_2^{+}$ state in ${}^{80}\mathrm{Ge}$.

Excited states in the neutron-rich nucleus ${}^{68}\mathrm{Fe}$ were populated using a ${}^9\mathrm{Be}$(${}^{68}\mathrm{Co}, {}^{68}\mathrm{Fe}+\gamma )\mathrm{X}$ charge-exchange reaction at 95 MeV/u. The new $\gamma$-ray transitions reported here for the first time complement data from $\beta$-decay studies and nucleon knockout reactions. In comparison to shell-model calculations with the LNPS effective interaction, two candidate states for the $6_1^{+}$ level emerge. The distinct population pattern of excited states and the magnitude of the cross section, ${\sigma }_{\mathrm{inc}}=0.51\left(6\right)$ mb, make this reaction a promising one for future in-beam $\gamma$-ray spectroscopy. Reaction calculations with nuclear structure input from a new, locally optimized Hamiltonian, $f7j4a$, together with general considerations for heavy-ion-induced charge-exchange reactions appear consistent with most of the observations, although challenges remain.

The $\beta$ decay of the isomeric and ground state of ${}^{50}\mathrm{Sc}$ to the semimagic nucleus ${}_{22}{}^{50}\mathrm{Ti}_{28}$ has been studied using a ${}^{50}\mathrm{Ca}$ beam delivered to the GRIFFIN $\gamma$-ray spectrometer at the TRIUMF-ISAC facility. $\beta$-decay branching ratios are reported to 16 excited states with a total of 38 $\gamma$-ray transitions linking them. These new data significantly expand the information available over previous studies. Relative intensities are measured to less than 0.001 $\%$ that of the strongest transition with the majority of $\gamma$-ray transitions observed here in $\beta$ decay for the first time. The data are compared with shell-model calculations utilizing both phenomenologically derived interactions employed in the $pf$ shell as well as a state-of-the-art ab initio-based interaction built in the valence-space in-medium similarity renormalization-group framework.

We discuss the construction of a nuclear energy density functional (EDF) from ab initio computations and advocate the need for a methodical approach that is free from ad hoc assumptions. The equations of state (EoSs) of symmetric nuclear and pure neutron matter are computed using the chiral ${\mathrm{NNLO}}_{\mathrm{sat}}$ and the phenomenological ${\mathrm{AV4}}^{\prime }+{\mathrm{UIX}}_c$ Hamiltonians as inputs to self-consistent Green's function (SCGF) and auxiliary field diffusion Monte Carlo (AFDMC) methods. We propose a convenient parametrization of the EoS as a function of the Fermi momentum and fit it on the SCGF and AFDMC calculations. We apply the ab initio based EDF to carry out an analysis of the binding energies and charge radii of different nuclei in the local density approximation. The ${\mathrm{NNLO}}_{\mathrm{sat}}$-based EDF produces encouraging results, whereas the ${\mathrm{AV4}}^{\prime }+{\mathrm{UIX}}_c$-based one is farther from experiment. Possible explanations of these different behaviors are suggested, and the importance of gradient and spin-orbit terms is analyzed. Our paper paves the way for a practical and systematic way to merge ab initio nuclear theory and density functional theory, while shedding light on some critical aspects of this procedure.