We investigated the probability distribution of thermal neutron capture cross sections (${\sigma }_{\mathrm{th}}$) deduced stochastically with the resonance parameters randomly sampled from Wigner and Porter-Thomas distributions. We found that the typical probability distribution has an asymmetric shape. While there is a long tail on the large ${\sigma }_{\mathrm{th}}$ side due to a resonance happening to be close to the thermal energy, the multiresonance contribution considerably reduces the probability on the small ${\sigma }_{\mathrm{th}}$ side. We also found that the probability distributions have a similar shape if nuclei have an average resonance spacing sufficiently larger than an average radiation width. We compared the typical probability distribution with the distribution of the experimental values of 193 nuclei and found a good agreement between them.

We calculate for the first time the shear viscosity of ultrarelativistic Boson systems in the presence of a Bose-Einstein condensate (BEC). Two different methods are used. One is the Grad's method of moments and another is the Green-Kubo relation within a kinetic transport approach. In this work we consider a Boson system with isotropic elastic collisions and a gluon system with elastic scatterings described by perturbation QCD (pQCD). The results show that the presence of a BEC lowers the shear viscosity. This effect becomes stronger for the increasing proportion of the BEC in the Boson system and is insensitive to the detail of interactions.

The baryon-quark phase transition is studied for the equation of state (EOS) of neutron star (NS) matter. The Thomas-Fermi (TF) approximation is employed in a semiclassical mean-field (MF) model for the EOS of baryonic matter including hyperons. The EOS of quark matter is also extracted from the Nambu–Jona-Lasinio (NJL) model. The phase transition from baryons to quarks is considered in the NS structure under the Maxwell and Gibbs constructions. Our findings for the maximum mass of NSs, as compared with the almost $2M_{\odot }$ pulsars $\mathrm{J}1614-2230$ and $\mathrm{J}0348+0432$, indicate that a region of baryon-quark mixed phase can exist in the inner core of NSs, while the existence of a pure phase is not allowed.

High-spin states in ${}^{193}\mathrm{Tl}$ were studied and the level scheme was revised and extended including the observation of new rotational bands. A surprising competition between bands built on the same $\pi h_{9/2}\otimes \nu {i_{13/2}}^{-2}$ nucleon configurations is observed. It is suggested that it is generated by two different rotational modes of this triaxial nucleus: (i) a rotation around the intermediate nuclear axis, producing a pair of chiral symmetry bands, and (ii) a rotation around the long nuclear axis, producing a third band with lower alignment.

In this paper, we reexamine the formulas of one-nucleon separation energies proposed and studied by Vogt [Phys. Lett. B 517, 255 (2001)] and by Bao [Phys. Rev. C. 87, 044313 (2013)], by considering the parities for both neutron number and proton number, and more sophisticated treatments of the shell effect and the fourth-order correction of the symmetry energy. The root-mean-squared deviation (RMSD) is 272 keV for one-neutron separation energy $S_n$ and 301 keV for one-proton separation energy $S_p$, in comparison with experimental data compiled in the AME2016 database, for nuclei with mass number $A>40$. With corrections of the radial basis function method, the RMSD is reduced to 147 and 151 keV for $S_n$ and $S_p$, respectively. We demonstrate, by numerical experiments of extrapolation from earlier versions of the AME databases to the AME2016 database, that our new formulas are very competitive in predicting one-nucleon separation energies as well as binding energies.

Background: High-accuracy and self-consistent fission product yield (FPY) data are needed to advance microscopic/macroscopic descriptions of the nuclear fission process, to improve the predictive power of phenomenological models, and for applications in nuclear energy, nuclear forensics, and homeland security.

Purpose: In a collaboration between the Triangle Universities Nuclear Laboratory (TUNL), Los Alamos National Laboratory (LANL), and Lawrence Livermore National Laboratory (LLNL), the dependence of a number of cumulative FPYs on the incoming neutron energy has been measured and unexpected energy dependencies of certain fission products have been reported [M. E. Gooden, Nucl. Data Sheets 131, 319 (2016)]. To investigate whether this observation is unique to neutron-induced fission, a program has been initiated to measure FPYs in photon-induced fission.

Method: The photon-induced FPYs were measured by a combination of fission counting using a specially designed dual-fission chamber and $\gamma$-ray counting. The measurements were carried out with a monoenergetic photon beam at the $\mathrm{HI}\gamma \mathrm{S}$ facility. Gamma-ray counting of the activated targets was performed with well-shielded high-purity germanium (HPGe) detectors over a period of two months after irradiation to properly identify the decay history of fission products.

Results: We report on our photofission product yield measurements on ${}^{235}\mathrm{U}$, ${}^{238}\mathrm{U}$, and ${}^{239}\mathrm{Pu}$ using a monoenergetic photon beam of $E_{\gamma }=13\mathrm{MeV}$. More than 40 fission products were uniquely identified, and their yield values were computed. The use of the fission chamber with post-activation measurements has provided absolute fission product yield data with minimal uncertainties.

Conclusion: The photon-induced cumulative fission product yields of ${}^{235}\mathrm{U}$, ${}^{238}\mathrm{U}$, and ${}^{239}\mathrm{Pu}$ are compared with previous photon- and neutron-induced fission measurements. In the near future data will be obtained at lower and higher photon energies.

Background: In the framework of the newly developed generalized energy density functional (EDF) called KIDS, the nuclear equation of state (EoS) is expressed as an expansion in powers of the Fermi momentum or the cubic root of the density (${\rho }^{1/3}$). Although an optimal number of converging terms was obtained in specific cases of fits to empirical data and pseudodata, the degree of convergence remains to be examined not only for homogeneous matter but also for finite nuclei. Furthermore, even for homogeneous matter, the convergence should be investigated with widely adopted various EoS properties at saturation.

Purpose: The first goal is to validate the minimal and optimal number of EoS parameters required for the description of homogeneous nuclear matter over a wide range of densities relevant for astrophysical applications. The major goal is to examine the validity of the adopted expansion scheme for an accurate description of finite nuclei.

Method: We vary the values of the high-order density derivatives of the nuclear EoS, such as the skewness of the energy of symmetric nuclear matter and the kurtosis of the symmetry energy, at saturation and examine the relative importance of each term in ${\rho }^{1/3}$ expansion for homogeneous matter. For given sets of EoS parameters determined in this way, we define equivalent Skyrme-type functionals and examine the convergence in the description of finite nuclei focusing on the masses and charge radii of closed-shell nuclei.

Results: The EoS of symmetric nuclear matter is found to be efficiently parameterized with only three parameters and the symmetry energy (or the energy of pure neutron matter) with four parameters when the EoS is expanded in the power series of the Fermi momentum. Higher-order EoS parameters do not produce any improvement, in practice, in the description of nuclear ground-state energies and charge radii, which means that they cannot be constrained by bulk properties of nuclei.

Conclusions: The minimal nuclear EDF obtained in the present work is found to reasonably describe the properties of closed-shell nuclei and the mass-radius relation of neutron stars. Attempts at refining the nuclear EDF beyond the minimal formula must focus on parameters which are not active (or strongly active) in unpolarized homogeneous matter, for example, effective tensor terms and time-odd terms.

In the first part of this paper, we use a nonlocal extension of the three-flavor Polyakov-Nambu-Jona-Lasinio model, which takes into account flavor-mixing, momentum dependent quark masses, and vector interactions among quarks, to investigate the possible existence of a spinodal region (determined by the vanishing of the speed of sound) in the QCD phase diagram and determine the temperature and chemical potential of the critical end point. In the second part of the paper, we investigate the quark-hadron composition of baryonic matter at zero as well as nonzero temperature. This is of great topical interest for the analysis and interpretation of neutron star merger events such as GW170817. With this in mind, we determine the composition of proto-neutron star matter for entropies and lepton fractions that are typical of such matter. These compositions are used to delineate the evolution of proto-neutron stars to neutron stars in the baryon-mass versus gravitational-mass diagram. The hot stellar models turn out to contain significant fractions of hyperons and $\mathrm{\Delta }$ isobars but no deconfined quarks. The latter are found to exist only in cold neutron stars.

The cumulative yields of 48 fission products in the mass range of 77–153 have been measured for the ${}^{232}\mathrm{Th}\left(n,f\right)$ reaction with the average neutron energies of 7.46, 13.4, and 18.0 MeV using an off-line γ-ray spectrometric technique. Fast neutron beams were generated using the ${}^9\mathrm{Be}\left(p,n\right)$ reaction with the proton energies of 25, 35, and 45 MeV from the MC-50 Cyclotron at the Korea Institute of Radiological and Medical Sciences. Post-neutron mass chain yields were obtained from the cumulative fission yields using the charge distribution correction of the medium energy. From the mass yield data, the peak-to-valley ratio, average light mass, and heavy mass, as well as the average neutron numbers were obtained. The fine structure of the mass yield distribution in the ${}^{232}\mathrm{Th}\left(n,f\right)$ reaction is explained by considering the nuclear structure effects such as the even–odd effect and shell closure proximity. The effect of deformed shells closure proximity arising due to the octupole deformation of fragments is discussed. The difference in the mass yield distribution between the ${}^{232}\mathrm{Th}\left(n,f\right)$ and ${}^{238}\mathrm{U}\left(n,f\right)$ reactions at various excitation energies is explained based on the different types of potential energy surfaces between the two fissioning systems. The role of excitation energy on the standard I and standard II asymmetric mode of fission is also discussed. In the ${}^{232}\mathrm{Th}\left(n,f\right)$ reaction with the excitation energies of 11–13 MeV, the onset of symmetric product yields, peak-to-valley ratio, average light mass, and heavy mass, as well as the average neutrons number have been observed, which are explained from the point of second chance fission.

A new formalism for the nonadiabatic collective inertia from time-dependent pairing equations for odd numbers of nucleons is described in detail. The effective masses and the moments of inertia result from the occurrence of matrix elements of the time derivatives and of the angular couplings, respectively, between states of different seniority configurations. For low collective velocities, the formulas for the inertia reduce to the known cranking expressions available for quasitationary states. The effective mass and the perpendicular moment of inertia are evaluated for the ${}^{230–232}\mathrm{Th}$ parent nuclei along the fission path. The inertia for the even-odd system is larger than those of the even-even ones and exhibits fluctuations due to the intrinsic nuclear structure. The ground state theoretical value of the moment of inertia for ${}^{231}\mathrm{Th}$ agrees well with the evaluated experimental data if the blocking effect is neglected.

High-spin states in ${}^{39}\mathrm{Ar}$ were populated using the ${}^{27}\mathrm{Al}({}^{14}\mathrm{C},pn)$ reaction at 25.6 MeV. The de-exciting $\gamma$ rays were measured with the FSU $\gamma$ detector array along with evaporation protons in a Si $E\text{−}\mathrm{\Delta }E$ telescope. The known high-spin level scheme was extended up to over 11 MeV with a dozen new levels above the neutron decay threshold. The decay pattern appears somewhat atypical for heavy-ion fusion-evaporation reactions. The structure of ${}^{39}\mathrm{Ar}$ is discussed in terms of the new FSU cross-shell $spsdpf$ interaction fitted to a wide range of nuclei. This interaction has proved quite successful in accounting for the level scheme of ${}^{39}\mathrm{Ar}$, including the previously suggested fully aligned $\pi f_{7/2}\otimes \nu f_{7/2}17/2^{+}$ state and previously discovered analogs of the lowest states in ${}^{39}\mathrm{Cl}$.

Lifetimes of intermediate-spin states in two rotational bands of ${}^{99}\mathrm{Zr}$ have been measured. These states were populated following the neutron-induced fission of ${}^{235}\mathrm{U}$ at the PF1B beamline of the Institut Laue-Langevin, Grenoble, during the EXILL-FATIMA campaign. The nucleus ${{}^{99}\mathrm{Zr}}_{59}$ exhibits shape coexistence and lies precisely on the border of an abrupt change in ground-state deformation when going from $N=58$ to $N=60$, making its study interesting for understanding the mechanisms involved in the rapid onset of deformation here. The $B\left(E2\right)$ values extracted for decays in the $\nu 3/2\left[541\right]$ band allow quadrupole deformations of ${\beta }_2=0.34\left(1\right)$ and 0.26(3) to be determined for the 821.6- and 1236.6-keV members, whereas ${\beta }_2=0.32\left(3\right)$ was found for the 850.5-keV member of the $\nu 3/2\left[411\right]$ band. Some of the excited states known in ${}^{99}\mathrm{Zr}$ have been reasonably described with interacting boson-fermion model (IBFM) calculations. Type-II shell evolution is proposed to play a major role in modifying single-particle energies in ${}^{99}\mathrm{Zr}$.

Neutron spin rotation is expected from quark-quark weak interactions in the standard model, which induce weak interactions among nucleons that violate parity. We present the results from an experiment searching for the effect of parity violation via the spin rotation of polarized neutrons in a liquid ${}^4\mathrm{He}$ medium. The value for the neutron spin rotation angle per unit length in ${}^4\mathrm{He}$, $d\varphi /dz=[+2.1\pm 8.3(\text{stat}.){}_{-0.2}^{+2.9}(\text{sys}.)]\times {10}^{-7}$ rad/m, is consistent with zero. The result agrees with the best current theoretical estimates of the size of nucleon-nucleon weak amplitudes from other experiments and with the expectations from recent theoretical approaches to weak nucleon-nucleon interactions. In this paper we review the theoretical status of parity violation in the $\vec{n}+{}^4\mathrm{He}$ system and discuss details of the data analysis leading to the quoted result. Analysis tools are presented that quantify systematic uncertainties in this measurement and that are expected to be essential for future measurements.

Half-lives of ${\beta }^{+}$ decay and electron capture are studied in some selected superheavy nuclei produced in hot-fusion reactions, namely, ${}^{290}\mathrm{Fl}$, ${}^{293}\mathrm{Mc}$, ${}^{294}\mathrm{Lv}$, and ${}^{295}\mathrm{Ts}$. The nuclear structure is described microscopically from deformed self-consistent Skyrme Hartree-Fock mean-field calculations that include pairing correlations. The sensitivity of the half-lives to deformation and to the $Q_{\mathrm{EC}}$ energies, which are still not determined experimentally, are studied. The results are compared with phenomenological $\alpha$-decay half-lives, showing that the latter decay mode is dominant in this mass region.

Background: Spontaneous fission events emit prompt neutrons correlated with one another in emission angle and energy. Measurements of these correlations can shed light on the partitioning of the excitation energy between the fragments, even if they are not directly measured.

Purpose: We explore the relationship in energy and angle between correlated prompt neutrons emitted from ${}^{252}\mathrm{Cf}$ spontaneous fission.

Methods: Measurements with the Chi-Nu array provide experimental data for coincident neutrons tagged with a fission chamber signal with ${10}^{\circ }$ angular resolution and 1-ns timing resolution for time-of-flight energy calculations. The experimental results are compared to simulations produced by the fission event generators cgmf, freya, and mcnpx-polimi ipol(1) = 1.

Results: We find that the measurements and the simulations all exhibit anisotropic neutron emission, although differences between fission event generators are evident.

Conclusions: This work shows that the dependence of detected neutron energy on the energy of another neutron detected in coincidence, although weak, is non-negligible, indicating that there may be correlations in energy between two neutrons emitted in the same fission event.

The fluid dynamics of a relativistic fireball with longitudinal and transverse expansion is described using a background-fluctuation splitting. Symmetry representations of azimuthal rotations and longitudinal boosts are used for a classification of initial state configurations and their fluid dynamic propagation in terms of a mode expansion. We develop an accurate and efficient numerical scheme based on the pseudospectral method to solve the resulting hyperbolic partial differential equations. Comparison to the analytically known Gubser solution underlines the high accuracy of this technique. We also present first applications of fluid dynamics with mode expansion (Fluidum) to central heavy ion collisions at the LHC energies featuring a realistic thermodynamic equations of state as well as shear and bulk viscous dissipation.

We report on high-precision $Q_{\mathrm{EC}}$ values of the ${}^{21}\mathrm{Na}\to {}^{21}\mathrm{Ne}$ and ${}^{23}\mathrm{Mg}\to {}^{23}\mathrm{Na}$ mirror $\beta$ transitions from mass measurements with ISOLTRAP at the CERN ISOLDE facility. A precision of $\delta m/m=9\times {10}^{-10}$ and $\delta m/m=1.5\times {10}^{-9}$ was reached for the masses of ${}^{21}\mathrm{Na}$ and ${}^{23}\mathrm{Mg}$, respectively. We reduce the uncertainty of the $Q_{\mathrm{EC}}$ values by a factor of 5, making them the most precise experimental input data for the calculation of the corrected $\mathcal{F}t$ value of these mixed Fermi and Gamow-Teller transitions. For the ${}^{21}\mathrm{Na}\to {}^{21}\mathrm{Ne}{Q}_{\mathrm{EC}}$ value, a $2.3\sigma$ deviation from the literature $Q_{\mathrm{EC}}$ value was found.

The equation of state (EOS) of infinite nuclear matter with a small proton or neutron fraction is a crucial input to determine the properties of neutron stars and compare model predictions to astronomical observations. The so-called symmetry energy is the part of the EOS accounting for the difference in the number of neutrons and protons. Numerous experiments have been devised to assess the symmetry energy and constrain its functional dependence with the nucleon density. Further constraints follow from a stellar modeling using the EOS to reproduce astronomical observations such as neutron star masses and radii. The recent detection of gravitational waves emitted from neutron star mergers and the nucleosynthesis ensuing from these events caused a surge of interest for such studies. Several types of nuclear reactions have been proposed to study the symmetry energy part of the EOS. Some of them consist in determining the neutron skin in nuclei and exploit its correlation with the slope parameter of the symmetry energy. In this article, we explore a particular set of reactions using high-energy ($E_{\mathrm{lab}}\sim 1$ GeV/nucleon) neutron-rich projectiles. We explore measurements of all reaction fragments (a) in the same isotopic chain, i.e., only by removal of neutrons, (b) in all charge-changing channels, and (c) total interaction cross sections. Using Hartree-Fock-Bogoliubov (HBF) predictions for neutron and proton densities with Skyrme interactions, we explore the sensitivity of these cross sections with the neutron skin in nuclei.

The high-spin states of the neutron-rich ${}^{81}\mathrm{Ga}$, with three valence protons outside a ${}^{78}\mathrm{Ni}$ core, were measured. The measurement involved prompt $\gamma$-ray spectroscopy of fission fragments isotopically identified using the combination of the variable mode spectrometer ($\mathrm{VAMOS}++$) and the advanced gamma tracking array (AGATA). The new $\gamma$-ray transitions, observed in coincidence with ${}^{81}\mathrm{Ga}$ ions, and the corresponding level scheme do not confirm the high-spin levels reported earlier. The newly observed high-spin states in ${}^{81}\mathrm{Ga}$ are interpreted using the results of state-of-the-art large-scale shell model (LSSM) calculations. The lower excitation energy levels are understood as resulting from the recoupling of three valence protons to the closed doubly magic core, while the highest excitation energy levels correspond to excitations of the magic $N=50$ neutron core. These results support the doubly magic character of ${}^{78}\mathrm{Ni}$ and the persistence of the $N=50$ shell closure but also highlight the presence of strong proton-neutron correlations associated with the promotion of neutrons across the magic $N=50$ shell gap, only few nucleons away from ${}^{78}\mathrm{Ni}$.

In this paper we present a method for efficiently including the effects of off-diagonal local rest frame momentum anisotropies in leading-order anisotropic hydrodynamics. The method relies on diagonalization of the spacelike block of the anisotropy tensor and allows one to reduce the necessary moments of the distribution function in the off-diagonal case to a linear combination of diagonal-anisotropy integrals. Once reduced to diagonal-anisotropy integrals, the results can be computed efficiently using techniques described previously in the literature. We present a general framework for how to accomplish this and provide examples for off-diagonal anisotropy moments entering into the energy-momentum tensor and viscous update equations which emerge when performing anisotropic pressure matching.