The $N=20$ and $N=28$ “islands of inversion” are described by large scale shell model calculations with an extension of the interaction SDPF-U that makes it possible to mix configurations with different $\mathrm{N}\hslash \omega$ or equivalently with different numbers of particles promoted from the $sd$ shell to the $pf$ shell. It allows to connect the classical $sd$-shell calculations below $N=18$ with the $sd$ (protons)-$pf$ (neutrons) calculations beyond $N=24–26$, for all the isotopes from oxygen to sulfur, using the same interaction. For some isotopes this range contains all the nuclei between the proton and the neutron drip lines and includes the $N=20$ and $N=28$ islands of inversion. We pay particular attention to the properties of the states at fixed $\mathrm{N}\hslash \omega$ which turn out to be the real protagonists of the physics at $N=20$. The existence of islands of inversion or deformation are explained as the result of the competition between the spherical mean field which favors the $0\hslash \omega$ configurations and the nuclear correlations which favor the deformed $N\hslash \omega$ configurations. The magnesium chain is exceptional because in it the $N=20$ and $N=28$ islands of inversion merge, enclosing all the isotopes between $N=19$ and $N=30$. Indeed, this would be also the case for the neon and sodium chains if their drip lines would reach $N=28$.

The radial basis function (RBF) is a powerful tool to improve mass predictions of nuclear models. By combining the RBF approach with the relativistic mean-field (RMF) model, the systematic deviations between mass predictions of the RMF model and the experimental data are eliminated to a large extent and the resulting rms deviation is reduced from $2.217$ to $0.488$ MeV. Furthermore, it is found that the RBF approach has a relatively reliable extrapolative power along the distance from the $\beta$-stability line except for a large uncertainty around the region at magic number. From the deduced neutron separation energies, we found that the description of the nuclear shell structure and shape transition is also significantly improved by the RBF approach, thus improving agreement with the solar $r$-process abundances before $A=130$ and speeding up the $r$-matter flow. Therefore, a shorter irradiation time is enough to reproduce the solar $r$-process abundance distribution for the improved RMF mass model, which is closer to the irradiation time for those sophisticated mass models.

The ${}^{236}\mathrm{Pu}(n,f)$, ${}^{237}\mathrm{Pu}(n,f)$ and ${}^{238}\mathrm{Pu}(n,f)$ cross sections have been inferred by utilizing the surrogate ratio method. Targets of ${}^{239}\mathrm{Pu}$ and ${}^{235}\mathrm{U}$ were bombarded with 28.5-MeV protons, and the light ion recoils, as well as fission fragments, were detected using the STARS detector array at the K150 Cyclotron at the Texas A&M cyclotron facility. The ($p$, $tf$) reaction on ${}^{239}\mathrm{Pu}$ and ${}^{235}\mathrm{U}$ targets was used to deduce the $\sigma$ $\left({}^{236}\mathrm{Pu}\right(n,f\left)\right)/\sigma$$\left({}^{232}\mathrm{U}\right(n,f\left)\right)$ ratio, and the ${}^{236}\mathrm{Pu}(n,f)$ cross section was subsequently determined for $E_n=0.5–7.5$ MeV. Similarly, the $(p,df$) reaction on the same two targets was used to deduce the $\sigma$$\left({}^{237}\mathrm{Pu}\right(n,f\left)\right)/\sigma$$\left({}^{233}\mathrm{U}\right(n,f\left)\right)$ ratio, and the ${}^{237}\mathrm{Pu}(n,f)$ cross section was extracted in the energy range $E_n=0.5–7$ MeV. The ${}^{238}\mathrm{Pu}(n,f)$ cross section was also deduced by utilizing the $(p,p^{\prime })$ reaction channel on the same targets. There is good agreement with the recent ENDF/B-VII.1 evaluated cross section data for ${}^{238}\mathrm{Pu}(n,f)$ in the range $E_n=0.5–10.5$ MeV and for ${}^{237}\mathrm{Pu}(n,f)$ in the range $E_n=0.5–7$ MeV; however, the ${}^{236}\mathrm{Pu}(n,f)$ cross section deduced in the present work is higher than the evaluation between 2 and 7 MeV.

Background: Fission-fragment charge-yield distributions exhibit a pronounced odd-even staggering. For actinide nuclei the staggering decreases with increasing proton number and with increasing excitation energy. In our calculations of fission yields [Phys. Rev. Lett. 106, 132503 (2011)] we obtained charge-yield distributions for a number of actinide nuclides by means of random walks on tabulated five-dimensional potential-energy surfaces. However, because the potential-energy model treats the system as a single, compound system during all stages of the fission process, in which individual fragment properties do not appear, no odd-even staggering appeared in the calculated yield curves.

Purpose: We have recently become aware that in the experimental data displayed in Fig. 1 in the above paper, there is a remarkable similarity in the odd-even staggering in fission of ${}^{240}\mathrm{Pu}$ at thermal neutron energy and fission of ${}^{234}\mathrm{U}$ in photon-induced fission at around 11 MeV. We discuss how this similarity and how the variation in the magnitude of the odd-even staggering for three Th isotopes with charge asymmetry and isotope can be qualitatively understood based on strongly damped shape evolution on our calculated five-dimensional potential-energy surfaces.

Methods: We conduct random walks on our tabulated five-dimensional potential-energy surfaces and study the difference between the total compound-nucleus energy and the potential energy for the different systems from saddle to scission. Under the strong-damping assumption this difference is the internal excitation energy. We also determine this quantity for different charge splits, symmetric and asymmetric.

Results: We find that the magnitude of the odd-even staggering in the charge distribution in the several cases studied here correlates well, inversely, with the excitation energy above the potential-energy surface in the postsaddle region.

Conclusions: Because the observed magnitude of the odd-even staggering correlates well with excitation energy over the region where the individual character of the fission fragments emerges, the Brownian shape-motion method can be expected to reproduce this feature, provided a potential-energy model is developed that accounts for how the nascent fragment properties are expressed in the calculated potential-energy surfaces.

The measurement of $1.97\pm 0.04M_{\mathrm{solar}}$ for PSR J1614-2230 and $2.01\pm 0.04M_{\mathrm{solar}}$ for PSR J0348 + 0432 puts a strong constraint on the neutron star equation of state and its exotic composition at higher densities. In this paper, we investigate the possibility of an exotic equation of state within the observational mass constraint of $2M_{\mathrm{solar}}$ in the framework of relativistic mean field model with density-dependent couplings. We particularly study the effect of antikaon condensates in the presence of hyperons on the mass-radius relationship of the neutron star.

We study the effects of density-dependent electromagnetic, axial, and weak vector form factors on the inclusive $(e,e^{\prime })$ reaction and the charged-current neutrino-nucleus scattering in the quasi-elastic region within the framework of a relativistic single-particle model. The density-dependent form factors obtained from a quark-meson coupling model are applied into the $(e,e^{\prime })$ reaction and the neutrino-nucleus scattering via charged current. The effects of the density-dependent form factors increase the $(e,e^{\prime })$ cross sections by a few percent. However, the effects may reduce the differential cross sections up to 20% (60%) at $\rho =1.0{\rho }_0\left(2.0{\rho }_0\right)$ for the antineutrino scattering and also reduce the cross section up to 20% (30%) at $\rho =1.0{\rho }_0\left(2.0{\rho }_0\right)$ for the neutrino scattering around the peak positions, where the normal density is ${\rho }_0\sim 0.15$ ${\mathrm{fm}}^{-3}$. For the density of finite nuclei such as ${}^{12}\mathrm{C}$, ${}^{40}\mathrm{Ca}$, and ${}^{208}\mathrm{Pb}$ as 0.6, 0.7, and 1.0 of ${\rho }_0$, the in-medium effects are 20% to 30%, even in the antineutrino case. Our theoretical double-differential and total cross sections are compared with the recent MiniBooNE data for ${}^{12}\mathrm{C}({\nu }_{\mu },{\mu }^{-})$ scattering.

By using two theoretical models (the postform finite range distorted wave Born approximation and the adiabatic model) we calculate the parallel momentum distribution of the charged core in the Coulomb breakup of Be isotopes on a heavy target at 100 MeV/nucleon. We show that the full width at half maxima of the parallel momentum distribution can be used to study the breakdown of the $N=8$ magic number away from the valley of stability.

An exclusive analysis of the four-body final states $\Lambda +p+{\pi }^{+}+K^0$ and ${\Sigma }^0+p+{\pi }^{+}+K^0$ measured with HADES for $p+p$ collisions at a beam kinetic energy of 3.5 GeV is presented. The analysis uses various phase space variables, such as missing mass and invariant mass distributions, in the four-particle event selection $(p$,${\pi }^{+}$,${\pi }^{+}$,${\pi }^{-})$ to find cross sections of the different production channels, contributions of the intermediate resonances ${\Delta }^{++}$ and $\Sigma {\left(1385\right)}^{+}$, and corresponding angular distributions. A dominant resonant production is seen, where the reaction $\Lambda +{\Delta }^{++}+K^0$ has a cross section about ten times higher $\left(29.45\pm 0.{08}_{-1.46}^{+1.67}\pm 2.06\mu \text{b}\right)$ than the analogous nonresonant reaction $\left(2.57\pm 0.{02}_{-1.98}^{+0.21}\pm 0.18\mu \text{b}\right)$. A similar result is obtained in the corresponding ${\Sigma }^0$ channels with $9.26\pm 0.{05}_{-0.31}^{+1.41}\pm 0.65\mu \text{b}$ in the resonant and $1.35\pm 0.{02}_{-1.35}^{+0.10}\pm 0.09\mu \text{b}$ in the nonresonant reactions.

The dependence of the spectral shape of produced charged hadrons on the size of a colliding system is discussed using a two-component model. As a result, the system-size hierarchy in spectral shape is observed. Next, a hydrodynamic extension of a two-component model for hadroproduction using recent theoretical calculations is suggested to describe the spectra of charged particles produced in heavy-ion collisions in the full range of transverse momenta $p_T$. Data from heavy-ion collisions measured at the Relativistic Heavy Ion Collider and the Large Hadron Collider are analyzed using the introduced approach and are combined in terms of energy density. The observed regularities might be explained by the formation of a quark-gluon plasma during the collision.

Ternary fission yields in the reaction ${}^{241}\mathrm{Pu}$$(n_{th},f)$ are calculated using a new model which assumes a nucleation-time-moderated chemical equilibrium in the low-density matter which constitutes the neck region of the scissioning system. The temperature, density, proton fraction, and fission time required to fit the experimental data are derived and discussed. A reasonably good fit to the experimental data is obtained. This model provides a natural explanation for the observed yields of heavier isotopes relative to those of the lighter isotopes, the observation of low proton yields relative to ${}^2\mathrm{H}$ and ${}^3\mathrm{H}$ yields, and the nonobservation of ${}^3\mathrm{He}$, all features which are shared by similar thermal neutron-induced and spontaneous fissioning systems.

The ground state two-proton decay lifetime of ${}^{19}\mathrm{Mg}$, populated by the one-neutron knockout of an intermediate-energy ${}^{20}\mathrm{Mg}$ radioactive beam, was measured utilizing a new experimental technique. A thin silicon detector positioned at varying distances (0.0–1.0 mm) downstream of the reaction target measured the energy loss of ${}^{19}\mathrm{Mg}$ and the two-proton decay product ${}^{17}\mathrm{Ne}$. The lifetime was deduced from fits to the measured energy-loss line shapes and depended upon the contribution of prompt reaction processes to the yield of ${}^{17}\mathrm{Ne}$. For relative ${}^{17}\mathrm{Ne}$ prompt contributions from 82% to 92%, the extracted lifetimes ranged from $1.{75}_{-0.42}^{+0.43}$ to $6.4_{-2.7}^{+2.4}$ ps. The results are consistent with the previously reported ${}^{19}\mathrm{Mg}$ lifetime measurement and serve as both an important complementary study and a validation of this new technique, which can provide lifetime information for short-lived states beyond the proton drip line.

The centrality dependence of midrapidity charged-particle multiplicities at a nucleon-nucleon center-of-mass energy of 2.76 TeV from CMS are compared to PHOBOS data at 200 and 19.6 GeV. The results are first fitted with a two-component model which parameterizes the separate contributions of nucleon participants and nucleon-nucleon collisions. A more direct comparison involves ratios of multiplicity densities per participant pair between the different collision energies. The results support and extend earlier indications that the influences of centrality and collision energy on midrapidity charged-particle multiplicities are to a large degree independent.

We analyze the form factors of the electromagnetic nucleon-to-Roper-resonance transition in the framework of a low-energy phenomenological field theory. A systematic power-counting procedure is generated by applying the complex-mass scheme. Within this power counting we calculate the form factors to next-to-next-to-leading order and fit the results to empirical data.

The past two decades have seen a revolution in ab initio calculations of nuclear properties. One key element has been the development of a rigorous effective interaction theory, applying unitary transformations to soften the nuclear Hamiltonian and hence accelerate the convergence as a function of the model space size. For consistency, however, one ought to apply the same transformation to other operators when calculating transitions and mean values from the eigenstates of the renormalized Hamiltonian. Working in a translationally invariant harmonic oscillator basis for the two- and three-nucleon systems, we evolve the Hamiltonian, square radius, and total dipole strength operators by the similarity renormalization group (SRG). The inclusion of up to three-body matrix elements in the ${}^4$He nucleus all but completely restores the invariance of the expectation values under the transformation. We also consider a Gaussian operator with adjustable range; short ranges have the largest absolute renormalization when including two- and three-body induced terms, while at long ranges the induced three-body contribution takes on increased relative importance.

We study the early stages of “central” $pA$ and peripheral $AA$ collisions. Several observables indicate that at a sufficiently large number of participant nucleons the system undergoes a transition into a new “explosive” regime. By defining a string-string interaction through the $\sigma$ meson exchange and performing molecular dynamics simulation, we argue that one should expect a strong collective implosion of the multistring “spaghetti” state, creating significant compression of the system in the transverse plane. Another consequence is the collectivization of the “$\sigma$ clouds” of all strings into a chirally symmetric fireball. We find that these effects happen provided the number of strings $N_s>30$ or so, as only such a number can compensate a small $\sigma$-string coupling. These findings should help us to understand the subsequent explosive behavior observed for the particle multiplicities roughly corresponding to this number of strings.

We comment on a recently published paper that has demonstrated that the increase in the electron-capture nuclear decay rate of ${}^7\mathrm{Be}$ in ${}^7\mathrm{BeO}$ under compression can be accounted for by the phase transformation of BeO from the wurtzite to the rock-salt structure.

The thermonuclear rate of the reaction ${}^{30}\mathrm{P}(p,\gamma ){}^{31}\mathrm{S}$ is important for interpreting nova nucleosynthesis in the $A\ge 30$ region. Estimates based on shell-model calculations are complicated by high level density and the presence of negative-parity states in the resonance region near the proton-emission threshold. We present results for the first time of calculations in a full $1\hslash \omega$ model space for the negative-parity states. Spectroscopic factors and proton-decay widths are calculated for input into the reaction rate. Available experimental data are used in conjunction with the calculations to obtain an estimate for the reaction rate. We show that the reaction rate will be uncertain to within about an order of magnitude until the position and decay widths of several of the key states in the region of 6.0 to 6.6 MeV are experimentally determined.