The ${}^{155}$Gd($n$,$\gamma$) reaction was measured with the DANCE $\gamma$-ray calorimeter at the Los Alamos Neutron Science Center. Spins were determined for the $s$-wave resonances by analysis of the $\gamma$-ray multiplicity distributions. The analysis was performed with a pattern recognition method. The resulting level densities for the $J=1$ and 2 resonances are in qualitative agreement with the expected 2$J$ $+$ 1 dependence. The average $s$-wave resonance spacing was determined to be $D_0=1.62$ $\pm$ 0.15 eV. Analysis of the neutron resonances with the code sammy yielded the $s$-wave strength function $S_0=1.99\pm 0.28\times {10}^{-4}$ and the average total radiative width ${\Gamma }_{\gamma }$ $=$ 120 $\pm$ 3 meV.

The postneutron yields of various fission products in the mass regions of 77–153 have been determined in the 50-, 60-, and 70-MeV bremsstrahlung-induced fission of ${}^{232}$Th by using a recoil catcher and an off-line γ-ray spectrometric technique in the electron linac at the Pohang Accelerator Laboratory, Korea. The mass-yield distributions were obtained from the fission-product yield data using charge-distribution corrections. The fission yields of the present paper and the existing data from the ${}^{232}$Th(γ,$f$) reaction at various energies are compared with those from the ${}^{232}$Th($n$,$f$), the ${}^{238}$U($n$,$f$), and the ${}^{238}$U(γ,$f$) reactions. We observe that the yields of fission products for $A$ = 133-134, $A$ = 138-139, $A$ = 143-144, and their complementary products in the above fissioning systems are higher than those of other fission products, which is explained based on the nuclear-structure effect. However, we observed that the yields of fission products for $A$ = 133-134 were lower than those for $A$ = 143-144 in the ${}^{232}$Th(γ,$f$) reaction compared to those of the ${}^{232}$Th($n$,$f$), ${}^{238}$U($n$,$f$), and ${}^{238}$U(γ,$f$) reactions. The yields of fission products for $A$ = 133-134 increase, but those for $A$ = 143-144 decrease with an increase in the excitation energy in the ${}^{232}$Th(γ,$f$) and ${}^{232}$Th($n$,$f$) reactions; however, those trends are reversed in the ${}^{238}$U(γ,$f$) and ${}^{238}$U($n$,$f$) reactions. The increasing or decreasing trends for the yields of fission products for $A$ = 133-134 and $A$ = 143-144 with the excitation energy in the ${}^{232}$Th(γ,$f$), ${}^{232}$Th($n$,$f$), ${}^{238}$U($n$,$f$), and ${}^{238}$U(γ,$f$) reactions are explained from the shell effect of the complementary products based on the static scission-point model and the standard I and II channels of bimodal fission. The peak-to-valley (P/V) ratio for the above fissioning systems also was obtained from the mass-yield distribution. The P/V ratio for the ${}^{232}$Th(γ,$f$) and ${}^{238}$U(γ,$f$) reactions at different energies from the present data and the existing literature data are interpreted to examine the role of excitation energy.

Well-known examples of shears bands in the nuclei ${}^{198}\mathrm{Pb}$ and ${}^{199}\mathrm{Pb}$ are investigated within tilted axis cranking relativistic mean-field theory. Energy spectra, the relation between spin and rotational frequency, deformation parameters and reduced $M1$ and $E2$ transition probabilities are calculated. The results are in good agreement with available data and with calculations based on the phenomenological pairing plus-quadrupole-quadrupole tilted-axis cranking model. It is shown that covariant density functional theory provides a successful microscopic and fully self-consistent description of magnetic rotation in the Pb region showing the characteristic properties as the shears mechanism and relatively large $B\left(M1\right)$ transitions decreasing with increasing spin.

Background: Antineutrino monitoring of reactors is an enhanced nuclear safeguard that is being explored by several international groups. A key question is whether such a scheme could be used to verify the destruction of plutonium loaded in a reactor as mixed oxide (MOX) fuel.

Purpose: To explore the effectiveness of antineutrino monitoring for the purposes of nuclear accountability and safeguarding of MOX plutonium, we examine the magnitude and temporal variation in the antineutrino signals expected for different loadings of MOX fuels.

Methods: Reactor burn simulations are carried out for four different MOX fuel loadings and the antineutrino signals as a function of fuel burnup are computed and compared.

Results: The antineutrino signals from reactor-grade and weapons-grade MOX are shown to be distinct from those from burning low enriched uranium, and this signal difference increases as the MOX plutonium fraction of the reactor core increases.

Conclusion: Antineutrino monitoring could be used to verify the destruction of plutonium in reactors, although verifying the grade of the plutonium being burned is found to be more challenging.

Hard photons emitted from energetic heavy-ion collisions are very interesting since they do not experience nuclear interaction, and therefore they are useful to explore properties of nuclear matter. We investigated hard-photon production and its properties in intermediate-energy heavy-ion collisions with the help of the Blotzmann-Uehling-Ulenbeck model. Two components of hard photons are discussed: direct and thermal. The positive directed flow parameter and negative elliptic flow parameter of direct photons are demonstrated and they are anticorrelated to the flows of free protons. The dependencies of hard-photon production and anisotropic parameters on impact parameter, beam energy, nuclear equation of state, and symmetry energy are also discussed. Furthermore, we investigated the two-photon momentum correlation function, from which the space-time structure information of the photon source could be extracted, as well as the two-photon azimuthal correlation, which could provide another good method to determine the elliptic flow parameter $v_2$ of direct hard photons.

We investigate how the initial geometry of a heavy-ion collision is transformed into final flow observables by solving event-by-event ideal hydrodynamics with realistic fluctuating initial conditions. We study quantitatively to what extent anisotropic flow ($v_n$) is determined by the initial eccentricity ${\varepsilon }_n$ for a set of realistic simulations, and we discuss which definition of ${\varepsilon }_n$ gives the best estimator of $v_n$. We find that the common practice of using an $r^2$ weight in the definition of ${\varepsilon }_n$ in general results in a poorer predictor of $v_n$ than when using $r^n$ weight, for $n>2$. We similarly study the importance of additional properties of the initial state. For example, we show that in order to correctly predict $v_4$ and $v_5$ for noncentral collisions, one must take into account nonlinear terms proportional to ${\varepsilon }_2^2$ and ${\varepsilon }_2{\varepsilon }_3$, respectively. We find that it makes no difference whether one calculates the eccentricities over a range of rapidity or in a single slice at $z=0$, nor is it important whether one uses an energy or entropy density weight. This knowledge will be important for making a more direct link between experimental observables and hydrodynamic initial conditions, the latter being poorly constrained at present.

The neutron-rich zirconium isotopes are a key testing ground for nuclear models due to their sensitivity to shape changes, and because they cross the $r$-process path of explosive nucleosynthesis. Furthermore, recent experimental data have revealed a high-spin isomer in ${}^{108}$Zr. Here we report the results of configuration-constrained potential-energy-surface calculations of ground states and high-$K$ states in ${}^{104–110}$Zr, restricted to quadrupole and hexadecapole shapes. These calculations enable the existing isomer data to be understood, and predictions are made for ${}^{110}$Zr.

The role of neutron transfer with positive $Q$-value in sub-barrier capture reactions ${}^{132}$Sn,${}^{130}$Te+${}^{58,64}$Ni, and ${}^{60}$Ni+${}^{100}$Mo, measured recently by Z. Kohley et al. [Phys. Rev. Lett. 107, 202701 (2011)] and F. Scarlassara et al. [EPJ Web Conf. 17, 05002 (2011)], is studied and explained within the quantum diffusion approach. It is shown that the transfer of two neutrons influences the sub-barrier capture through the change of the deformations of the colliding nuclei. Based on our analysis, one can understand why the influence of the neutron transfer is strong in some capture reactions, but is weak in others.

A dynamically constrained phase-space coalescence model was proposed and was used first to predict the light nuclei (antinuclei) yield, transverse momentum distribution, and the rapidity distribution in nonsingle diffractive $pp$ collisions at $\sqrt{s}=7$ and 14 TeV. This calculation was based on the $1.2\times {10}^8$ hadronic final states generated with the pythia and paciae models. The pythia and paciae model results of antideuteron yields of $4.852\times {10}^{-5}$ and $6.247\times {10}^{-5}$ at $\sqrt{s}=7\mathrm{TeV}$ are compatible with the ALICE preliminary datum of $5.456\times {10}^{-5}$ (or $\sim 6\times {10}^{-5}$).

We explore the interplay between renormalization, charge independence and charge symmetry breaking (CIB and CSB) in $S$-wave nucleon-nucleon scattering. The renormalizability requirement generates universality functions, that is, correlations between the low-energy scattering observables in the neutron-neutron, neutron-proton, and proton-proton systems. The universality functions only depend on the (known) form of the nucleon-nucleon potential at long distances and, in particular, they do not require any assumptions about short-range CIB and CSB effects. In addition, the inclusion of Coulomb effects is trivial for the particular case of proton-proton scattering, allowing us to relate strong and Coulomb scattering observables. Within this approach, and using a one-boson-exchange potential, the previous correlations are shown to be phenomenologically satisfied without the need to introduce further parameters.

A new generation of local three-body potentials providing an excellent description of the properties of light nuclei, as well as of the neutron-deuteron doublet scattering length, has been recently derived. We have performed a comparative analysis of the equations of state of both pure neutron matter (PNM) and symmetric nuclear matter (SNM) at zero temperature obtained using these models of three-nucleon forces. In particular, we have carried out both variational and auxiliary field diffusion Monte Carlo calculations of the equation of state of PNM, while in the case of SNM we have only the variational approach has been considered. None of the considered potentials simultaneously explains the empirical equilibrium density and binding energy of symmetric nuclear matter. However, two of them provide reasonable values of the saturation density. The ambiguity concerning the treatment of the contact term of the chiral inspired potentials is discussed.

Systematic calculations of fission barriers allowing for triaxial deformation are performed for even-even superheavy nuclei with charge number $Z=112–120$ using three classes of covariant density functional models. The softness of nuclei in the triaxial plane leads to an emergence of several competing fission paths in the region of the inner fission barrier in some of these nuclei. The outer fission barriers are considerably affected by triaxiality and octupole deformation. General trends of the evolution of the inner and the outer fission barrier heights are discussed as a function of the particle numbers.

There is a possibility that small traces of long-lived superheavy elements ($Z⩾104$) still exist in nature. An ultrasensitive search for such superheavy elements has been conducted at the Maier-Leibnitz Laboratory in Garching (Germany) by means of accelerator mass spectrometry. A sample of raw platinum has been scanned for 13 different masses in the range $292⩽A⩽310$. The masses $A=292$ and 298 were scanned in pure osmium and pure lead fluoride, respectively. For each mass, several hours of background-free data were recorded. Since no events could be attributed to superheavy elements, upper limits on their abundances in the sample materials on the order of ${10}^{-14}$–${10}^{-16}$ were established.

Using the Hartree-Fock plus random phase approximation ($\mathrm{HF}+\mathrm{RPA}$), we study the impurity effect of $\Lambda$ hyperon on the collective vibrational excitations of double-$\Lambda$ hypernuclei. To this end, we employ Skyrme-type $\Lambda N$ and $\Lambda \Lambda$ interactions for the HF calculations, and the residual interactions for the RPA are derived with the same interactions. We find that the inclusion of two $\Lambda$ hyperons in ${}^{16}$O shifts the collective states toward higher energies. In particular, the energy of the giant monopole resonance of ${}_{\Lambda \Lambda }^{18}$O, as well as that of ${}_{\Lambda \Lambda }^{210}$Pb, becomes higher. This implies that the effective incompressibility modulus increases owing to the impurity effect of $\Lambda$ particles, if the $\beta$-stability condition is not imposed.

We present Penning-trap mass measurements of neutron-rich ${}^{44,47-50}$K and ${}^{49,50}$Ca isotopes carried out at the TITAN facility at TRIUMF-ISAC. The ${}^{44}$K mass measurement was performed with a charge-bred 4$+$ ion utilizing the TITAN electron beam ion trap and agrees with the literature. The mass excesses obtained for ${}^{47}$K and ${}^{49,50}$Ca are more precise and agree with the values published in the 2003 Atomic Mass Evaluation (AME’03). The ${}^{48,49,50}$K mass excesses are more precise than the AME’03 values by more than 1 order of magnitude. For ${}^{48,49}$K, we find deviations of 7$\sigma$ and 10$\sigma$, respectively. The new ${}^{49}$K mass excess lowers significantly the two-neutron separation energy at the neutron number $N=30$ compared with the separation energy calculated from the AME’03 mass-excess values and thus increases the $N=28$ neutron-shell gap energy at $Z=19$ by approximately 1 MeV.

We study the strangeness production in antiproton-nucleus collisions at beam momenta from 200 MeV/$c$ to 15 GeV/$c$ and in $\overline{p}$ annihilation at rest within the Giessen Boltzmann-Uehling-Uhlenbeck (GiBUU) transport model. The GiBUU model contains a very detailed description of underlying antinucleon-nucleon cross sections, in particular, of the strangeness production channels. We compare our calculations with experimental data on $\Lambda$, $K_S^0$, and $\overline{\Lambda }$ production in $\overline{p}$A collisions and with earlier intranuclear cascade calculations. The contributions of various partial channels to the hyperon production are reported and systematic differences with the experiment are discussed. The possible formation of bound $\Lambda$- and $\Lambda \Lambda$-nucleus systems is also considered. Finally, results on the $\Xi$ hyperon production are presented in view of forthcoming experiments with antiproton beams at the Facility for Antiproton and Ion Research.

The dependence of the fusion-fission process on Skyrme forces is studied by using the dynamical cluster-decay model (DCM) and the $\ell$-summed extended-Wong model in the ${}^{132}\mathrm{Sn}+{}^{64}\mathrm{Ni}\to {{}^{196}\mathrm{Pt}}^{*}$ reaction, where the nuclear proximity potential is obtained by using the semiclassical extended Thomas-Fermi (ETF) approach in the Skyrme energy density formalism (SEDF) under the frozen density approximation. The DCM gives an excellent fit to the measured fusion evaporation residue (ER) and the fission cross sections below and above barrier energies, with ER data needing “barrier lowering” at below-barrier energies for each Skyrme force (an in-built property of the DCM). The fission cross sections show a contribution of quasifission (qf) at the above-barrier two or three highest energies, depending on the Skyrme force. Calculations are illustrated for three Skyrme forces, GSkI, SSk, and SIII. Another interesting result is that there is a change of fission mass distribution from a predominantly asymmetric one to a symmetric one with a decrease in the $N/Z$ ratio of the compound nucleus, independent of the choice of nuclear interaction potential, which gives an opportunity to address the isospin effects in the Pt${}^{*}$ nucleus. Within the $\ell$-summed extended-Wong model we find that the GSkI and SSk forces fit the total fusion cross-section data exactly, whereas the SIII force needs “barrier modification” in order to fit the data at below-barrier energies. This happens because the isospin and neutron-proton asymmetry nature of GSkI and SSk forces is different from that of the SIII force, and because the center-of-mass energy $E_{\mathrm{c}.\mathrm{m}.}$ dependence of the barrier height for the SIII force and that of Blocki et al. [Ann. Phys. (NY) 105, 427 (1977)] differs strongly (by a constant amount of $\sim$7 MeV) from those for GSKI and SSk forces. Note that, because of the associated preformation factor with each fragment, the DCM has the advantage of treating various decay processes separately, whereas the Wong model describes only the total fusion cross section, a sum of cross sections due to all contributing processes.

In this paper we study the influence of hadronic resonances on the phase diagram calculated with an effective chiral flavor SU(3) model. We show that varying the couplings of the baryonic resonances to the attractive scalar and the repulsive vector fields has a major impact on the order and location of the chiral phase transition and the possible existence of a critical end point, as well as on the thermodynamic properties of the model. Furthermore, we study (strange) quark number fluctuations and show the related susceptibilities both at zero baryochemical potential and when crossing the phase transition line at three different points in the $T$–$\mu$ plane. We obtain the best agreement with current lattice data if we choose a rather strong vector coupling, which in our model limits the phase transition to a smooth crossover and implies the nonexistence of a critical end point.

We compute nucleon and Roper electromagnetic elastic and transition form factors using a Poincaré-covariant, symmetry-preserving treatment of a $\mathrm{vector}\times \mathrm{vector}$ contact interaction. Obtained thereby, the electromagnetic interactions of baryons are typically described by hard form factors. In contrasting this behavior with that produced by a momentum-dependent interaction, one achieves comparisons which highlight that elastic scattering and resonance electroproduction experiments probe the evolution of the strong interaction's running masses and coupling to infrared momenta. For example, the existence, and location if so, of a zero in the ratio of nucleon Sachs form factors are strongly influenced by the running of the dressed-quark mass. In our description of the nucleon and its first excited state, diquark correlations are important. These composite and fully interacting correlations are instrumental in producing a zero in the Dirac form factor of the proton's $d$ quark and in determining the ratio of $d$-to-$u$ valence-quark distributions at $x=1$, as we show via a simple formula that expresses $d_v/u_v(x=1)$ in terms of the nucleon's diquark content. The contact interaction produces a first excitation of the nucleon that is constituted predominantly from axial-vector diquark correlations. This impacts greatly on the ${\gamma }^{*}p\to P_{11}\left(1440\right)$ form factors, our results for which are qualitatively in agreement with the trend of available data. Notably, our dressed-quark core contribution to $F_{2*}\left(Q^2\right)$ exhibits a zero at $Q^2\approx 0.5m_N^2$. Faddeev equation treatments of a hadron's dressed-quark core usually underestimate its magnetic properties; hence, we consider the effect produced by a dressed-quark anomalous electromagnetic moment. Its inclusion much improves agreement with experiment. On the domain $0<Q^2\lesssim 2$GeV${}^2$, meson-cloud effects are conjectured to be important in making a realistic comparison between experiment and hadron structure calculations. We find that our computed helicity amplitudes are similar to the bare amplitudes inferred via coupled-channels analyses of the electroproduction process. This supports a view that extant hadron structure calculations, which typically omit meson-cloud effects, should directly be compared with the bare masses, couplings, etc., determined via coupled-channels analyses.