We continue our previous study of level dynamics in the [O(6)–U(5)]⊃O(5) transition of the interacting boson model [Phys. Rev. C 73, 014306 (2006)] by using the semiclassical theory of spectral fluctuations. We find classical monodromy, related to a singular bundle of orbits with infinite period at energy $E=0$, and bifurcations of numerous periodic orbits for $E>0$. The spectrum of allowed ratios of periods associated with β and γ vibrations exhibits an abrupt change around zero energy. These findings explain anomalous bunching of quantum states in the $E\approx 0$ region, which is responsible for the redistribution of levels between O(6) and U(5) multiplets.

Momentum correlation functions of nucleon-nucleon pairs are presented for reactions with C isotopes bombarding a ${}^{12}C$ target within the framework of the isospin-dependent quantum molecular dynamics model. The binding-energy dependence of the momentum correlation functions is also explored, and other factors that have an influence on momentum correlation functions are investigated. These factors include momentum-dependent nuclear equations of state, in-medium nucleon-nucleon cross sections, impact parameters, total pair momenta, and beam energy. In particular, the rise and the fall of the strength of momentum correlation functions at lower relative momentum are shown with an increase in beam energy.

The random phase approximation (RPA) long-range correlations are known to play a significant role in understanding the depletion of single particle-hole states observed in ($e,e^{\text{'}}$) and ($e,e^{\text{'}}p$) measurements. Here the RPA theory, implemented using the D1S force is considered for the specific purpose of building correlated ground states and related one-body density matrix elements. These may be implemented and tested in a fully microscopic optical model for NA scattering off doubly closed-shell nuclei. A method is presented to correct for the correlations overcounting inherent to the RPA formalism. One-body density matrix elements in the uncorrelated (i.e., Hartree-Fock) and correlated (i.e., RPA) ground states are then challenged in proton scattering studies based on the Melbourne microscopic optical model to highlight the role played by the RPA correlations. Agreement between the parameter free scattering predictions and measurements is good for incident proton energies ranging from 200 MeV down to approximately 60 MeV and becomes gradually worse in the lower energy range. Those features point unambiguously to the relevance of the g-matrix method to build microscopic optical model potentials at medium energies, and emphasize the need to include nucleon-phonon coupling, that is, a second-order component of the Feshbach type in the potential at lower energies. Illustrations are given for proton scattering observables measured up to 201 MeV for the ${}^{16}\mathrm{O}$, ${}^{40}\mathrm{Ca}$, ${}^{48}\mathrm{Ca}$, and ${}^{208}\mathrm{Pb}$ target nuclei.

The reaction ${\pi }^{-}d\to \mathit{nn}\gamma$ is calculated in chiral perturbation theory so as to facilitate an extraction of the neutron-neutron scattering length ($a_{\mathit{nn}}$). We include all diagrams up to $O(Q^3)$. This includes loop effects in the elementary ${\pi }^{-}p\to \gamma n$ amplitude and two-body diagrams, both of which were ignored in previous calculations. We find that the chiral expansion for the ratio of the quasi-free (QF) to final-state-interaction (FSI) peaks in the final-state neutron spectrum converges well. Our third-order calculation of the full spectrum is already accurate to better than 5%. Extracting $a_{\mathit{nn}}$ from the shape of the entire ${\pi }^{-}d\to \mathit{nn}\gamma$ spectrum by using our calculation in its present stage would thus be possible at the $\pm 0.8$ fm level. A fit to the FSI peak only would allow an extraction of $a_{\mathit{nn}}$ with a theoretical uncertainty of $\pm 0.2$ fm. The effects that contribute to these error bars are investigated. The uncertainty in the nn rescattering wave function dominates. This suggests that the quoted theoretical error of $\pm 0.3$ fm for the most recent ${\pi }^{-}d\to \mathit{nn}\gamma$ measurement may be optimistic. The possibility of constraining the nn rescattering wave function used in our calculation more tightly—and thus reducing the error—is briefly discussed.

We have calculated the ground-state energy of the doubly magic nuclei ${}^4\mathrm{He}$, ${}^{16}\mathrm{O}$, and ${}^{40}\mathrm{Ca}$ within the framework of the Goldstone expansion starting from various modern nucleon-nucleon potentials. The short-range repulsion of these potentials has been renormalized by constructing a low-momentum potential $V_{\mathrm{low}-k}$. We have studied the connection between the cutoff momentum Λ and the size of the harmonic oscillator space employed in the calculations. We have found a fast convergence of the results with a limited number of oscillator quanta.

Experimental data of the nuclear β-decay half-lives are systematically analyzed and investigated. We have discovered a new formula for the ${\beta }^{+}$-decay half-lives of nuclei far from the β-stable line. It is stated that the logarithm of the half-life of ${\beta }^{+}$ decay with a same order depends linearly on the neutron number of parent nuclei along any isotopic chain. This shows that there is a new exponential law between the half-life of the ${\beta }^{+}$ decay and the nucleon number ($Z,N$). The possible physics behind this new law is discussed. Experimental data are well reproduced by this simple and accurate formula with four parameters. This new formula can be used to predict the ${\beta }^{+}$-decay half-lives of nuclei far from stability. It is useful for experimental physicists to analyze the data of ${\beta }^{+}$ decay.

A Monte Carlo simulation of the fission fragment statistical decay based on a sequential neutron followed by γ-ray emission is proposed. The γ-ray energy spectrum is calculated as a function of the mass of the fission fragments and integrated over the whole mass distribution. The prompt γ-ray multiplicity distribution, both the average number of emitted γ rays and the average γ-ray energy as a function of the mass of the fission fragments [respectively, ${\overline{N}}_{\gamma }(A)$ and $\langle {\varepsilon }_{\gamma }\rangle (A)$], are also assessed. The γ-γ correlations emitted from both light and heavy fragments are calculated as well as correlations between γ-ray energies. Results are reported for the neutron-induced fission of ${}^{235}\mathrm{U}$ (at 0.53 MeV neutron energy) and for the spontaneous fission of ${}^{252}\mathrm{Cf}$.

The thermal neutron radiative capture cross section for the K isomeric state in ${}^{177}\mathrm{Lu}$ has been measured for the first time. Several ${}^{177}\mathrm{Lu}$${}^m$ targets have been prepared and irradiated in various neutron fluxes at the Laüe Langevin Institute in Grenoble and at the CEA reactors OSIRIS and ORPHEE in Saclay. The method consists of measuring the ${}^{178}\mathrm{Lu}$ activity by $\gamma$-ray spectroscopy. The values obtained in four different neutron spectra have been used to calculate the resonance integral of the radiative capture cross section for ${}^{177}\mathrm{Lu}$${}^m$. In addition, an indirect method leads to the determination of the ${}^{177}\mathrm{Lu}$${}^g$ neutron radiative capture cross section.

We show that all four of the nucleon form factors can be very well explained using the manifestly covariant spectator theory. The nucleon is modeled as a spherical state of three constituent quarks with electromagnetic form factors, all determined by the fit to the data.

The location of the ($\gamma ,p)/(\gamma ,n$) and ($\gamma ,\alpha )/(\gamma ,n$) line at γ process temperatures is discussed, using updated reaction rates based on global Hauser-Feshbach calculations. The results can be directly compared with classic γ process discussions. The nuclei exhibiting the largest sensitivity to uncertainties in nuclear structure and reaction parameters are specified, and suggestions for experiments are made. Additionally, the effect of employing two recent global α+nucleus potentials is discussed. It is found that branchings at higher mass depend more sensitively on these potentials. The case of ${}^{146}\mathrm{Sm}$/${}^{144}\mathrm{Sm}$ production is addressed separately. Also, in this case the more recent α+nucleus potentials seem to address the issues concerning the production of these Sm isotopes in massive stars. In conclusion, it is found that it is unlikely that the calculated underproduction of p nuclides in the Mo-Ru region is due to nuclear physics deficiencies but that problems at higher mass number may still be solved by improved nuclear input.

The energy and momentum lost by a hard parton propagating through hot and dense matter has to be redistributed in the nuclear medium. Apart from heating the medium, there is the possibility that collective modes are excited. We outline a formalism that can be used to track the propagation of such a mode through the evolving medium if its dispersion relation is known. Under the assumption that a sound wave is created, we track the jet energy loss as a function of spacetime and follow the resulting mach cone throughout the fireball evolution. We compare with the angular correlation pattern of hard hadrons as obtained by the PHENIX Collaboration and find good agreement with the data provided that a substantial fraction of jet energy (∼90%) is deposited into a propagating mode and that the hot matter can be characterized by an equation of state with a soft point (not necessarily a mixed phase).

We calculate nucleon-nucleon cross sections in the nuclear medium with unequal densities of protons and neutrons. We use the Dirac-Brueckner-Hartree-Fock approach together with realistic nucleon-nucleon potentials. We examine the effect of asymmetry in neutron and proton concentrations and find that it can be significant for scattering of identical nucleons. Numerical results are included for potential applications in transport equations.

We report the development of a new shell model Monte Carlo algorithm, which uses the proton-neutron formalism. Shell model Monte Carlo methods, within the isospin formulation, have been succesfully used in large-scale shell model calculations. Motivation for this work is to extend the feasibility of these methods to shell model studies involving nonidentical proton and neutron valence spaces. We show the feasibility of the new approach with some test results. Finally, we use a realistic nucleon-nucleon interaction in the model space described by $(1p_{1/2},0g_{9/2})$ proton and $(1d_{5/2},2s_{1/2},1d_{3/2},0g_{7/2},0h_{11/2})$ neutron orbitals above the ${}^{88}\mathrm{Sr}$ core to calculate ground-state energies, binding energies, $B(E2)$ strengths, and to study pairing properties of the even-even ${}^{90-104}\mathrm{Zr}$ and ${}^{92-106}\mathrm{Mo}$ isotope chains.

The β-decay process of the ${}^6\mathrm{He}$ halo nucleus into the $\alpha +d$ continuum is studied in a three-body model. The ${}^6\mathrm{He}$ nucleus is described as an $\alpha +n+n$ system in hyperspherical coordinates on a Lagrange mesh. The convergence of the Gamow-Teller matrix element requires the knowledge of wave functions up to about 30 fm and of hypermomentum components up to $K=24$. The shape and absolute values of the transition probability per time and energy units of a recent experiment can be reproduced very well with an appropriate $\alpha +d$ potential. A total transition probability of $1.6\times {10}^{-6}$ s${}^{-1}$ is obtained in agreement with that experiment. Halo effects are shown to be very important because of a strong cancellation between the internal and halo components of the matrix element, as observed in previous studies. The forbidden bound state in the $\alpha +d$ potential is found essential to reproduce the order of magnitude of the data. Comments are made on R-matrix fits.

An extensive and consistent coupled-channel analysis of the elastic, inelastic, one- and two-neutron transfer, and fusion experimental cross sections for the ${}^{18}\mathrm{O}$+${}^{58}\mathrm{Ni}$ system, in the energy range $35.1\le E_{\mathrm{LAB}}\le 65.0$ MeV, is described. In the calculations, we have used the São Paulo potential as the bare interaction. Our results show a quite different role played by the peripheral couplings on the fusion process as compared with previous analyses using simplified coupled-channel models. The results reported in the present work are an important tool for understanding the recently reported systematic failure of the Woods-Saxon nuclear potential to describe both fusion and elastic scattering processes.

This is the second of two articles that investigate cold dilute neutron matter on the lattice using pionless effective field theory. In the unitary limit, where the effective range is zero and scattering length is infinite, simple scaling relations relate thermodynamic functions at different temperatures. When the second virial coefficient is properly tuned, we find that the lattice results obey these scaling relations. We compute the energy per particle, pressure, spin susceptibility, dineutron correlation function, and an upper bound for the superfluid critical temperature.

The absolute astrophysical S factor and cross section for the ${}^7\mathrm{Li}$($d,n_0$)${}^8\mathrm{Be}$ and ${}^7\mathrm{Li}$($d,n_1$)${}^8\mathrm{Be}$ reactions have been determined using deuteron beams with energies between 45 and 80 keV. The slope of the S factor is consistent with zero in the $n_0$ case but is slightly negative in the $n_1$ case. The S factor for the sum of both neutron groups at c.m. energies below 70 keV is $S(E)=5400(\pm 1500)-37(\pm 21)E$ keV b, where E is the c.m. energy in keV.

The neutron capture cross sections of the radioactive isotope ${}^{151}\mathrm{Sm}$ and of natural samarium have been measured in the energy range from 3 keV to 225 keV at the Karlsruhe 3.7 MV Van de Graaff accelerator. Neutrons were produced via the ${}^7\mathrm{Li}$($p,n$)${}^7\mathrm{Be}$ reaction by bombarding metallic Li targets with a pulsed proton beam and capture events were registered with the Karlsruhe 4π Barium Fluoride Detector. The cross sections were determined relative to the gold standard using a 206 mg sample of samarium oxide with 90% enrichment in ${}^{151}\mathrm{Sm}$. Over most of the measured energy range uncertainties of ~2–3% could be achieved for the ${}^{151}\mathrm{Sm}$/${}^{197}\mathrm{Au}$ ratio. Maxwellian averaged neutron capture cross sections of ${}^{151}\mathrm{Sm}$ were calculated for thermal energies between kT = 8 keV and 100 keV with due consideration of the stellar enhancement factor and were found to be systematically larger than all previous theoretical predictions used in the analysis of the s-process branching at ${}^{151}\mathrm{Sm}$. In the context of the branching analysis, an experimental determination of the stellar enhancement factor due to captures in thermally excited states is proposed, and the tentative determination of the p-process residual of ${}^{152}\mathrm{Gd}$ and a few other cases is discussed.

The nucleosynthesis of elements beyond iron is dominated by the s and r processes. However, a small amount of stable isotopes on the proton-rich side cannot be made by neutron capture and are thought to be produced by photodisintegration reactions on existing seed nuclei in the so-called “p process.” So far most of the p-process reactions are not yet accessible by experimental techniques and have to be inferred from statistical Hauser-Feshbach model calculations. The parametrization of these models has to be constrained by measurements on stable proton-rich nuclei. A series of (n,γ) activation measurements, related by detailed balance to the respective photodisintegrations, were carried out at the Karlsruhe Van de Graaff accelerator using the ${}^7\mathrm{Li}$(p,n)${}^7\mathrm{Be}$ source for simulating a Maxwellian neutron distribution of kT = 25 keV. First results for the experimental (n,γ) cross sections of the light p nuclei ${}^{74}\mathrm{Se}$ and ${}^{84}\mathrm{Sr}$ are reported. These experimental values were used for an extrapolation to the Maxwellian averaged cross section at 30 keV, $\langle \sigma \rangle {}_{30}$, yielding 271 ± 15 mb for ${}^{74}\mathrm{Se}$, and 300 ± 17 mb for the total capture cross section of ${}^{84}\mathrm{Sr}$. The partial cross section to the isomer in ${}^{85}\mathrm{Sr}$ was found to be 190 ± 10 mb.

From the analysis of $\gamma \text{−}\gamma \text{−}\gamma$ coincidence data taken with Gammasphere of the prompt γ rays in the spontaneous fission of ${}^{252}\mathrm{Cf}$, the $2^{+}\to 0^{+}$ transition in ${}^{88}\mathrm{Se}$ was identified for the first time. Also, the $4^{+}\to 2^{+}$ and $6^{+}\to 4^{+}$ transitions in ${}^{86}\mathrm{Se}$ were identified along with four new states above $4^{+}$ in ${}^{84}\mathrm{Se}$. Surprisingly, the $2^{+}$ energy rises in ${}^{88}\mathrm{Se}$ compared to ${}^{86}\mathrm{Se}$. This increase in energy could arise from the interaction of a low-lying excited $0^{+}$ state with different deformation and the $0^{+}$ ground state to depress the ground-state energy.