Free nucleons propagating in water are known to produce $\gamma$ rays, which form a background to the searches for diffuse supernova neutrinos and sterile neutrinos carried out with Cherenkov detectors. As a consequence, the process of nucleon knockout induced by neutral-current quasielastic interactions of atmospheric (anti)neutrinos with oxygen needs to be under control at the quantitative level in the background simulations of ongoing and future experiments. In this paper, we provide a quantitative assessment of the uncertainty associated with the theoretical description of the nuclear cross sections, estimating it from the discrepancies between the predictions of different models.

The half-life of the superallowed Fermi ${\beta }^{+}$ emitter ${}^{18}\mathrm{Ne}$ has been determined via two high-precision $\beta$ counting experiments at TRIUMF's Isotope Separator and Accelerator facility. Using two different $4\pi$ continuous-flow gas-proportional counters, two independent measurements were made, yielding a weighted average of $T_{1/2}=1.{66400}_{-0.00048}^{+0.00057}$ s, which is consistent with but approximately 2 times more precise than a previous high-precision measurement based on $\gamma$-ray counting. The present work achieves $\pm 0.034\%$ precision for the ${}^{18}\mathrm{Ne}$ half-life and will enable the inclusion of ${}^{18}\mathrm{Ne}$ among the set of precisely measured superallowed Fermi $\beta$-decay $ft$ values once improved measurements are made for its $Q$ value and superallowed branching ratio. As a test of systematic uncertainties, the half-life of ${}^{23}\mathrm{Ne}$ was measured and the world average has been improved, by a factor of 1.7, to $37.148\pm 0.032$ s.

Differential cross sections for elastic scattering of photons from the deuteron have recently been measured at the Tagged-Photon Facility at the MAX IV Laboratory in Lund, Sweden. These first new measurements in more than a decade further constrain the isoscalar electromagnetic polarizabilities of the nucleon and provide the first-ever results above 100 MeV, where the sensitivity to the polarizabilities is increased. We add 23 points between 70 and 112 MeV, at angles ${60}^{\circ }$, ${120}^{\circ }$, and ${150}^{\circ }$. Analysis of these data using a chiral effective field theory indicates that the cross sections are both self-consistent and consistent with previous measurements. Extracted values of ${\alpha }_s=[12.1\pm 0.8(\mathrm{stat})\pm 0.2(\mathrm{BSR})\pm 0.8\left(\mathrm{th}\right)]\times {10}^{-4}{\mathrm{fm}}^3$ and ${\beta }_s=[2.4\pm 0.8(\mathrm{stat})\pm 0.2(\mathrm{BSR})\pm 0.8\left(\mathrm{th}\right)]\times {10}^{-4}{\mathrm{fm}}^3$ are obtained from a fit to these 23 new data points. This paper presents in detail the experimental conditions and the data analysis used to extract the cross sections.

We explore the thermal properties of hot and dense matter using a model that reproduces the empirical properties of isospin symmetric and asymmetric bulk nuclear matter, optical-model fits to nucleon-nucleus scattering data, heavy-ion flow data in the energy range 0.5–2 GeV/$A$, and the largest well-measured neutron star mass of $2M_{\odot }$. This model, which incorporates finite range interactions through a Yukawa-type finite range force, is contrasted with a conventional zero range Skyrme model. Both models predict nearly identical zero-temperature properties at all densities and proton fractions, including the neutron star maximum mass, but differ in their predictions for heavy-ion flow data. We contrast their predictions of thermal properties, including their specific heats, and provide analytical formulas for the strongly degenerate and nondegenerate limits. We find significant differences in the results of the two models for quantities that depend on the density derivatives of nucleon effective masses. We show that a constant value for the ratio of the thermal components of pressure and energy density expressed as ${\mathrm{\Gamma }}_{\text{th}}=1+(P_{\text{th}}/{\varepsilon }_{\text{th}})$, often used in simulations of proto-neutron stars and merging compact object binaries, fails to adequately describe results of either nuclear model. The region of greatest discrepancy extends from subsaturation densities to a few times the saturation density of symmetric nuclear matter. Our results suggest alternate approximations for the thermal properties of dense matter that are more realistic.

We systematize the available experimental material concerning $\alpha$-decay transitions to low-lying excited states in even-even and odd-mass emitters. We generalize our previous theoretical prediction concerning the linear dependence between hindrance factors and the excitation energy for transitions in even-even $\alpha$ emitters. Thus, we show that $\alpha$ intensities for transitions to excited states depend linearly upon the excitation energy for all known even-even and odd-mass $\alpha$ emitters. It turns out that the well-known Viola-Seaborg law for $\alpha$-decay transitions between ground states can be generalized for transitions to excited states. This rule can be used to predict any $\alpha$-decay half-life to a low-lying excited state.

Background: The deviation between different model calculations that may occur when one goes toward regions where the masses are unknown is getting increased attention. This is related to the uncertainties of the different models which may have not been fully understood.

Purpose: To explore in detail the effect of the isospin dependence of the spin-orbital force in the Woods-Saxon potential on global binding energy and deformation calculations.

Method: The microscopic energies and nuclear deformations of about 1850 even-even nuclei are calculated systematically within the macroscopic-microscopic framework using three Woods-Saxon parametrizations, with different isospin dependencies, which were constructed mainly for nuclear spectroscopy calculations. Calculations are performed in the deformation space $({\beta }_2,\gamma ,{\beta }_4)$. Both the monopole and doubly stretched quadrupole interactions are considered for the pairing channel.

Results: The ground-state deformations obtained by the three calculations are quite similar to each other. Large differences are seen mainly in neutron-rich nuclei and in superheavy nuclei. Systematic calculations on the shape-coexisting second minima are also presented. As for the microscopic energies of the ground states, the results are also very close to each other. Only in a few cases the difference is larger than 2 MeV. The total binding energy is estimated by adding the macroscopic energy provided by the usual liquid drop model with its parameters fitted through the least square root and minimax criteria. Calculations are also compared with the results of other macroscopic-microscopic mass models.

Conclusions: All the three calculations give similar values for the deformations, microscopic energies, and binding energies of most nuclei. One may expect to have a better understanding of the isospin dependence of the spin-orbital force with more data on proton- and neutron-rich nuclei.

Accurate isotopic molybdenum nuclear data are important because molybdenum can exist in nuclear reactor components including fuel, cladding, or as a high yield fission product. High-resolution time-of-flight neutron transmission measurements on highly enriched isotopic metallic samples of ${}^{95}\mathrm{Mo}$, ${}^{96}\mathrm{Mo}$, ${}^{98}\mathrm{Mo}$, and ${}^{100}\mathrm{Mo}$ were performed in the resonance energy range from 1 to $620\mathrm{keV}$. The measurements were taken with the newly developed modular ${}^6\mathrm{Li}$-glass transmission detector positioned at the 100-m experimental flight station. In the unresolved energy region (URR), new comprehensive methods of analysis were developed and validated in order to obtain accurate neutron total cross-section data from the measurement by correcting for background and transmission enhancement effects. Average parameters and fits to the total cross section for ${}^{95}\mathrm{Mo}$ were obtained using the Hauser-Feshbach statistical model code fitacs, which is currently incorporated into the sammy code. The fits to the experimental data deviate from the current evaluated nuclear data file/B-VII.1 isotopic Mo evaluations by several percent in the URR.

We have studied the dissociation of quarkonia states in a deconfined medium of quarks and gluons at the large baryon chemical potential and small temperature region. The aim of this study is to probe the dense baryonic medium expected to be produced at the Facility for Anti-proton and Ion Research, GSI Darmstadt. This is done by correcting both the short- and long-distance terms of the Cornell potential by a dielectric function, embodying the effects of deconfined quarks and gluons, at finite baryon chemical potential and temperature. It is found that $J/\psi$ is dissociated approximately at 1.4 ${\mu }_c$ in the temperature range 20–50 MeV, which can indirectly help to locate the point on the quantum chromodynamics phase diagram at the large chemical potential and low-temperature zone.

A study using UrQMD is presented concerning the higher moments of net protons from Au + Au collisions at 7.7, 11.5, 14.6, 19.6, 27, 39, 62.4, and 200 GeV, concentrating on $C_4/C_2=\kappa {\sigma }^2$. Higher moments of net protons are predicted to be a sensitive probe of the critical point of QCD. At the QCD critical point, particular ratios of the moments of net protons are predicted to differ from the Poisson baseline. Recently the STAR Collaboration has published the higher moments of net protons for Au + Au collisions at $\sqrt{s_{NN}}=7.7$, 11.5, 19.6, 27, 39, 62.4, and 200 GeV. UrQMD quantitatively reproduces STAR's measured $C_4/C_2=\kappa {\sigma }^2$ for net protons for all Au + Au collisions more central than 30% and at all centralities for $\sqrt{s_{NN}}=7.7$ and 11.5 GeV. The effects are investigated of three different centrality definitions on the values of $C_4/C_2=\kappa {\sigma }^2$ from UrQMD calculations including the impact parameter given by UrQMD. It is shown that using a centrality definition based on multiplicity to calculate the higher moments of net protons gives a biased answer for $C_4/C_2=\kappa {\sigma }^2$, except in the most central bin (0–5%).

The relativistic interacting quark-diquark model, constructed in the framework of point form dynamics, is extended to strange baryons. The strange and nonstrange baryon spectra are calculated and compared with the experimental data.

Forty-six decay chains, assigned to the decay of ${}^{288}115$, were produced using the ${}^{243}\mathrm{Am}({}^{48}\mathrm{Ca},3n){}^{288}115$ reaction at the Lawrence Berkeley National Laboratory 88-in. cyclotron. The resulting series of $\alpha$ decays were studied using $\alpha$-photon and $\alpha$-x-ray spectroscopies. Multiple $\alpha$-photon coincidences were observed in the element 115 decay chain members, particularly in the third- and fourth-generation decays (presumed to be ${}^{280}\mathrm{Rg}$ and ${}^{276}\mathrm{Mt}$, respectively). Upon combining these data with those from 22 ${}^{288}115$ decay chains observed in a similar experiment, updated level schemes in ${}^{276}\mathrm{Mt}$ and ${}^{272}\mathrm{Bh}$ (populated by the $\alpha$ decay of ${}^{280}\mathrm{Rg}$ and ${}^{276}\mathrm{Mt}$, respectively) are proposed. Photons were observed in the energy range expected for $K$ x rays coincident with the $\alpha$ decay of both ${}^{280}\mathrm{Rg}$ and ${}^{276}\mathrm{Mt}\mathrm{.}$ However, Compton scattering of higher-energy $\gamma$ rays and discrete transitions are present in the $K$ x-ray region preventing a definitive $Z$ identification to be made based on observation of characteristic $K$ x-ray energies.

The excited states in ${}^{12}\mathrm{C}$ are investigated by using an extended version of the so-called Tohsaki-Horiuchi-Schuck-Röpke (THSR) wave function, where both the $3\alpha$ condensate and ${}^8\mathrm{Be}+\alpha$ cluster asymptotic configurations are included. A new method is also used to resolve spurious continuum coupling with physical states. I focus on the structures of the “Hoyle band” states ($0_2^{+},2_2^{+}$, and $4_2^{+}$), which were recently observed above the Hoyle state, and of the $0_3^{+}$ and $0_4^{+}$ states, which were also quite recently identified in experiment. Their resonance parameters and decay properties are reasonably reproduced. All these states have dilute density structure of the $3\alpha$ or ${}^8\mathrm{Be}+\alpha$ clusters with larger root mean square radii than that of the Hoyle state. The Hoyle band is not simply considered to be the ${}^8\mathrm{Be}\left(0^{+}\right)+\alpha$ rotation as suggested by previous cluster model calculations, nor to be a rotation of a rigid-body triangle-shaped object composed of the $3\alpha$ particles. This is mainly due to the specificity of the Hoyle state, which has the $3\alpha$ condensate structure and gives rise to the $0_3^{+}$ state with a prominent ${}^8\mathrm{Be}\left(0^{+}\right)+\alpha$ structure as a result of very strong monopole excitation from the Hoyle state.

In this paper, the electron screening effects on $\alpha$-decay half-lives are investigated in different external environments, including $\alpha$ decays in neutral atoms, in metal, and in extremely strong magnetic-field environments. Systematic calculations of $\alpha$-decay half-lives are performed for $\alpha$ emitters with proton number $Z=52$–105. By taking into account the electron screening effects, the interaction potential between $\alpha$ particle and daughter nucleus, and the decay energy are both changed in external environments. From the numerical results, it is found that the $\alpha$-decay half-lives in external environments are changed by a factor of from $5\times {10}^{-4}$% to 11.46% due to the electron screening effects. Moreover, we find that the electron screening effect is closely related to the decay energy of the bare nucleus and its proton number. To measure the electron screening effects in experiments, it is suggested to select the $\alpha$-decay candidates with relatively low decay energies and proper decay half-lives.

Elements of nuclear symmetry energy evaluated from different energy density functionals parametrized by fitting selective bulk properties of few representative nuclei are seen to vary widely. Those obtained from experimental data on nuclear masses across the periodic table, however, show that they are better constrained. A possible direction in reconciling this paradox may be gleaned from comparison of results obtained from use of the binding energies in the fitting protocol within a microscopic model with two sets of nuclei, one a representative standard set and another where very highly asymmetric nuclei are additionally included. A covariance analysis reveals that the additional fitting protocol reduces the uncertainties in the nuclear symmetry energy coefficient, its slope parameter, as well as the neutron-skin thickness in ${}^{208}\mathrm{Pb}$ nucleus by $\sim 50\%\mathrm{.}$ The central values of these entities are also seen to be slightly reduced.

Quadrupole and octupole stiffnesses in the ground states of even-even ${}^{112-150}\mathrm{Ba}$ isotopes have been systematically investigated by means of potential-energy-surface calculations. The calculations are carried out in both $\left({\beta }_2,\gamma ,{\beta }_4\right)$ and (${\beta }_2,{\beta }_3,{\beta }_4,{\beta }_5$) deformation spaces with the inclusion of triaxial and reflection-asymmetric shape degrees of freedom, respectively. The present results are compared with previous calculations and available experiments. The shape instabilities are evaluated by analyzing the potential energy curves with respect to both the quadrupole and octupole deformations, which is consistent with the previous discussions predicting the $\gamma$ softness or triaxiality and octupole instability. In addition, taking the near-drip-line ${}^{114}\mathrm{Ba}$ nucleus as an example, we briefly investigate the effects of potential parameters (e.g., the strength of the spin-orbit potential $\lambda$, and the nuclear surface diffuseness $a$) on the deformation energy curve, showing almost negligible modifications of nuclear shape and stiffness but considerable changes in the depth of the minimum and the height of the fission barrier (which may be very important for the study of heavy and superheavy nuclei).

We report new data on the ${}^{136}\mathrm{Sb}{6}^{-}$ yrast isomer with $T_{1/2}=489\left(40\right) \mathrm{ns}$ and $\pi g_{7/2}^1\times \nu f_{7/2}^3$ configuration, populated in the projectile fission of ${}^{238}\mathrm{U}$ on a ${}^9\mathrm{Be}$ target. The analysis confirms the lifetime, providing a good accuracy measurement. In addition, the decay of the isomer to the ground state is newly suggested. Our result for the isomeric decay scheme is in a good agreement with shell-model calculations.

Background: It has been recently shown that some Skyrme functionals can lead to nonconverging results in the calculation of some properties of atomic nuclei. A previous study has pointed out a possible link between these convergence problems and the appearance of finite-size instabilities in symmetric nuclear matter (SNM) around saturation density.

Purpose: We show that the finite-size instabilities not only affect the ground-state properties of atomic nuclei, but they can also influence the calculations of vibrational excited states in finite nuclei.

Method: We perform systematic fully-self consistent random phase approximation (RPA) calculations in spherical doubly magic nuclei. We employ several Skyrme functionals and vary the isoscalar and isovector coupling constants of the time-odd term $\mathbf{s}·\mathrm{\Delta }\mathbf{s}$. We determine critical values of these coupling constants beyond which the RPA calculations do not converge because the RPA stability matrix becomes nonpositive.

Results: By comparing the RPA calculations of atomic nuclei with those performed for SNM we establish a correspondence between the critical densities in the infinite system and the critical coupling constants for which the RPA calculations do not converge.

Conclusions: We find a quantitative stability criterion to detect finite-size instabilities related to the spin $\mathbf{s}·\mathrm{\Delta }\mathbf{s}$ term of a functional. This criterion could be easily implemented in the standard fitting protocols to fix the coupling constants of the Skyrme functional.

We construct a model to describe dense hadronic matter at zero and finite temperatures, based on the parity doublet model of DeTar and Kunihiro [C. E. DeTar and T. Kunihiro, Phys. Rev. D 39, 2805 (1989)], including the isosinglet scalar meson $\sigma$ as well as $\rho$ and $\omega$ mesons. We show that, by including a six-point interaction of the $\sigma$ meson, the model reasonably reproduces the properties of normal nuclear matter with the chiral invariant nucleon mass $m_0$ in the range from 500 to 900 MeV. Furthermore, we study the phase diagram based on the model, which shows that the value of the chiral condensate drops at the liquid-gas phase transition point and at the chiral phase transition point. We also study asymmetric nuclear matter and find that the first-order phase transition for the liquid-gas phase transition disappears in asymmetric matter and that the critical density for the chiral phase transition at nonzero density becomes smaller for larger asymmetry.

A multitude of discrete $2^{+}$ states in ${}^{124}\text{Sn}$ with energy up to 5 MeV were populated and identified with the $({}^{17}\text{O}$, ${}^{17}\mathrm{O}^{\prime }\gamma )$ reaction at 340 MeV. Cross sections were compared with distorted wave Born approximation predictions and in general a good agreement was found. The measured energy and intensity distributions of the $2^{+}$ states are very similar to the predictions based on self-consistent density functional theory and extended QRPA approach accounting for multiphonon degrees of freedom. This provides evidence of the excitation of the pygmy quadrupole resonance in skin nuclei.