A model independent formalism for the electron positron annihilation reaction $e^{+}+e^{-}\to a_1(1260)+\pi$ has been derived. The differential and total cross sections and the elements of the spin-density matrix of the $a_1$-meson were calculated in terms of the electromagnetic form factors of the corresponding ${\gamma }^{*}{a}_1\pi$ current. Simple models of $a_1$ form factors have been fitted to the available cross section data and they allow to give numerical predictions for the different observables.

We calculate the rate of neutron–mirror-neutron oscillations for ultracold neutrons trapped in a storage vessel. Recent experimental bounds on the oscillation time are discussed.

Online measurements of the magnetic dipole moments and isotope shifts of ${}^{58}\mathrm{Cu}$ and ${}^{59}\mathrm{Cu}$ by the in-source laser spectroscopy method are reported. The results for the magnetic moments are $\mu$ (${}^{58}\mathrm{Cu}$) $=+0.52(8)\hspace{0.5em}{\mu }_N,\mu$(${}^{59}\mathrm{Cu}$) $=+1.84(3)\hspace{0.5em}{\mu }_N$ and for the isotope shifts $\delta {\nu }^{59,65}=1.72(22)$ GHz and $\delta {\nu }^{58,65}=1.99(30)$ GHz in the transition from the $3d^{10}4s\hspace{0.17em}$${}^2\mathrm{S}$${}_{1/2}$ ground state to the $3d^{10}4p\hspace{0.17em}$${}^2\mathrm{P}$${}_{1/2}$ state in Cu I. The magnetic moment of ${}^{58}\mathrm{Cu}$ is discussed in the context of the strength of the subshell closure at ${}^{56}\mathrm{Ni}$, additivity rules and large-scale shell model calculations.

The triaxial-octupole $Y_{32}$ correlation in atomic nuclei has long been expected to exist but experimental evidence has not been clear. We find, in order to explain the very low-lying $2^{-}$ bands in the transfermium mass region, that this exotic effect may manifest itself in superheavy elements. Favorable conditions for producing triaxial-octupole correlations are shown to be present in the deformed single-particle spectrum, which is further supported by quantitative Reflection Asymmetric Shell Model calculations. It is predicted that the strong nonaxial-octupole effect may persist up to the element 108. Our result thus represents the first concrete example of spontaneous breaking of both axial and reflection symmetries in the heaviest nuclear systems.

Recent studies of the hot fusion reaction ${}^{248}\mathrm{Cm}$(${}^{26}\mathrm{Mg}$,$\mathit{xn}$)${}^{274\text{−}x}\mathrm{Hs}$ have provided new nuclear decay data on ${}^{265,266}\mathrm{Sg}$ and confirmed the existence of an isomeric state in ${}^{261}\mathrm{Rf}$. The results reported in [J. Dvorak et al., Phys. Rev. Lett. 100, 132503 (2008)] suggest that all decay chains observed in previous studies of the reaction ${}^{248}\mathrm{Cm}$(${}^{22}\mathrm{Ne}$,$\mathit{xn}$)${}^{270\text{−}x}\mathrm{Sg}$, which were originally attributed to ${}^{266}\mathrm{Sg}$, originated from ${}^{265}\mathrm{Sg}$. Here, the decay properties of ${}^{265}\mathrm{Sg}$ are reevaluated. Indications for the existence of an isomeric state in ${}^{265}\mathrm{Sg}$ are found. The half-lives and main $\alpha$ particle energies of the two ${}^{265}\mathrm{Sg}$ states are 8.9 s/8.85 MeV and 16.2 s/8.70 MeV, respectively. Direct production of this isotope as an evaporation residue of a nuclear fusion reaction populates both states with similar intensity while $\alpha$ decay of ${}^{269}\mathrm{Hs}$ into ${}^{265}\mathrm{Sg}$ preferentially populates the longer-lived state, which in turn decays almost exclusively into the short-lived state in ${}^{261}\mathrm{Rf}$. The cross section of the reaction ${}^{248}\mathrm{Cm}$(${}^{22}\mathrm{Ne}$,$5n$)${}^{265}\mathrm{Sg}$ is reanalyzed and found to be of the order of a few hundred pb, assuming that $\alpha$ decay is the only decay mode of ${}^{265}\mathrm{Sg}$. A decay scheme that is consistent with the published data on ${}^{265}\mathrm{Sg}$ and ${}^{261}\mathrm{Rf}$ is proposed, which can serve as a working hypothesis in the design of new experiments dedicated to study the production and decay of these two isotopes.

We argue that selected $S$ wave meson-baryon channels may play a key role in matching poor baryon mass predictions from quark models with data. The identification of these channels with effective inelastic channels in data analysis allows us to derive a prescription that could improve the extraction and identification of baryon resonances.

We derive the long-range contributions to the tree-nucleon force at next-to-next-to-next-to-leading order in the chiral expansion. We give both momentum- and coordinate-space representations.

We investigate the pairing correlations in neutron-rich Mg and Cr isotopes by paying special attention to the roles of continuum states and neutron skins. By performing the coordinate space Hartree-Fock-Bogoliubov calculation with the density-dependent contact pairing force, we show that the predicted pairing properties strongly depend on not only isoscalar but also isovector density dependence of the pairing force. We propose that the moment of inertia of the low-lying rotational excitations can provide desirable information to construct a reliable pairing density functional for exploring the novelty of the pairing correlations in neutron-rich nuclei close to the drip line.

We study the properties of strange quark matter in equilibrium with normal nuclear matter. Instead of using the conventional bag model in quark sector, we achieve the confinement by a density-dependent quark mass derived from in-medium chiral condensates. In nuclear matter, we adopt the equation of state from the Brueckner-Bethe-Goldstone approach with three-body forces. It is found that the mixed phase can occur, for a reasonable confinement parameter, near the normal nuclear saturation density and goes over to pure quark matter at about 5 times the saturation. The onset of mixed and quark phases is compatible with the observed class of low-mass neutron stars, but it hinders the occurrence of kaon condensation.

The PHENIX experiment has measured the suppression of semi-inclusive single high-transverse-momentum ${\pi }^0$'s in Au+Au collisions at $\sqrt{s_{\mathit{NN}}}=200$ GeV. The present understanding of this suppression is in terms of energy loss of the parent (fragmenting) parton in a dense color-charge medium. We have performed a quantitative comparison between various parton energy-loss models and our experimental data. The statistical point-to-point uncorrelated as well as correlated systematic uncertainties are taken into account in the comparison. We detail this methodology and the resulting constraint on the model parameters, such as the initial color-charge density ${\mathit{dN}}^g/\mathit{dy}$, the medium transport coefficient $\langle \widehat{q}\rangle$, or the initial energy-loss parameter ${\epsilon }_0$. We find that high-transverse-momentum ${\pi }^0$ suppression in Au+Au collisions has sufficient precision to constrain these model-dependent parameters at the ±20–25% (one standard deviation) level. These constraints include only the experimental uncertainties, and further studies are needed to compute the corresponding theoretical uncertainties.

We present an optimization scheme that employs a genetic algorithm (GA) to determine the properties of low-lying nucleon excitations within a realistic photo-pion production model based upon an effective Lagrangian. We show that with this modern optimization technique it is possible to reliably assess the parameters of the resonances and the associated error bars as well as to identify weaknesses in the models. To illustrate the problems the optimization process may encounter, we provide results obtained for the nucleon resonances $\Delta (1230)$ and $\Delta (1700)$. The former can be easily isolated and thus has been studied in depth, while the latter is not as well known experimentally.

We determined the absolute branch of the $T=2$ superallowed decay of ${}^{32}\mathrm{Ar}$ by detecting the ${\beta }^{+}$-delayed protons and γ decays of the daughter state. We obtain $b_{\mathrm{SA}}^{\beta }=(22.71\pm 0.16)\%$, which represents the first determination of a proton branch to better than 1%. Using this branch along with the previously determined ${}^{32}\mathrm{Ar}$ half-life and energy release, we determined $\mathit{ft}=(1552\pm 12)$ s for the superallowed decay. This $\mathit{ft}$ value, together with the corrected $\mathcal{F}t$ value extracted from previously known $T=1$ superallowed decays, yields a measurement of the isospin symmetry breaking correction in ${}^{32}\mathrm{Ar}$ decay ${\delta }_C^{\exp }=(2.1\pm 0.8)\%$. This can be compared to a theoretical calculation ${\delta }_C=(2.0\pm 0.4)\%$. As by-products of this work, we determined the γ and proton branches for the decay of the lowest $T=2$ state of ${}^{32}\mathrm{Cl}$, made a precise determination of the total proton branch and relative intensities of proton groups that leave ${}^{31}\mathrm{S}$ in its first excited state and deduced an improved value for the ${}^{32}\mathrm{Cl}$ mass.

Some thermodynamical magnitudes of interest in a pure neutron plasma are studied within the framework of the nonrelativistic Hartree-Fock approximation at finite density and temperature. We use Skyrme and Gogny forces to describe such a neutron plasma and study the main differences that arise in these two effective parametrizations of the nuclear interaction when a strong magnetic field induces a permanent magnetization in the gas. The existence of a nonzero permanent spin polarization in a neutron plasma is explored in the density-temperature parameter space. We find that for moderate temperatures and in the low-density range up to densities $\approx 0.5{\rho }_0$ both parametrizations predict that as density decreases an increasingly strong magnetization is allowed. In the range $0.5{\rho }_0\lesssim \rho \lesssim 3{\rho }_0$ there is an approximately constant polarization that can be as big as $\approx 12\%$ for the maximum allowed interior magnetic field $B\approx {10}^{18}$ G. For higher densities there is a dramatic difference in the polarization trend followed by Skyrme an Gogny forces. Although the former predict a ferromagnetic phase transition, the Gogny forces prevent it keeping the magnetization below $5\%$.

The approximate selection rules for the interband and intraband electromagnetic transitions are predicted referring to two quantum numbers, which are derived from an algebraic solution for the particle-rotor model with one high$-j$ nucleon coupled to a triaxially deformed core. It is shown that the inclusion of angular momentum dependence for moments of inertia reproduces the experimental excitation energies relative to a reference quite well both for positive and negative parity TSD bands in ${}^{161,163,165,167}$Lu.

We investigate the simultaneous explanation of the ${}^6\mathrm{He}+{}^{12}\mathrm{C}$ elastic and inelastic scattering and ${}^6\mathrm{He}+{}^{12}\mathrm{C}\to {}^4\mathrm{He}+{}^{14}\mathrm{C}$ transfer reaction observables at 18.0 MeV within the framework of the coupled-channels Born approximation. In obtaining the microscopic double folding potentials, two different nucleon densities deduced from the no-core shell model and few-body model calculations for the ${}^6\mathrm{He}$ have been used. Although a good agreement between theoretical results and experimental data has been obtained for elastic scattering and transfer reactions data, the theoretical results underestimate the magnitude of the inelastic-$2^{+}$ state data. We present in this article that the deformation of the imaginary part of the optical potential is very important and it overcomes the magnitude problem for the inelastic data for this system.

Recent attempts to determine the pion polarizability by dispersion relations yield values that disagree with the predictions of chiral perturbation theory. These dispersion relations are based on specific forms for the absorptive part of the Compton amplitudes. The analytic properties of these forms are examined, and the strong enhancement of intermediate-meson contributions is shown to be connected with spurious singularities. If the basic requirements of dispersion relations are taken into account, the results of dispersion theory and effective field theory are not inconsistent.

An approach to the equation of state for the inner crust of neutron stars based on Skyrme-type forces is presented. Working within the Wigner-Seitz picture, the energy is calculated by the TETF (temperature-dependent extended Thomas-Fermi) method, with proton shell corrections added self-consistently by the Strutinsky-integral method. Using a Skyrme force that has been fitted to both neutron matter and to essentially all the nuclear mass data, we find strong proton shell effects: proton numbers $Z=50,40$, and 20 are the only values possible in the inner crust, assuming that nuclear equilibrium is maintained in the cooling neutron star right down to the ambient temperature. Convergence problems with the TETF expansion for the entropy, and our way of handling them, are discussed. Full TETF expressions for the specific heat of inhomogeneous nuclear matter are presented. Our treatment of the electron gas, including its specific heat, is essentially exact, and is described in detail.

We discuss relations and differences between two methods for the construction of unitarily transformed effective interactions, the Similarity Renormalization Group (SRG) and Unitary Correlation Operator Method (UCOM). The aim of both methods is to construct a soft phase-shift equivalent effective interaction which is well suited for many-body calculations in limited model spaces. After contrasting the two conceptual frameworks, we establish a formal connection between the initial SRG-generator and the static generators of the UCOM transformation. Furthermore we propose a mapping procedure to extract UCOM correlation functions from the SRG evolution. We compare the effective interactions resulting from the UCOM-transformation and the SRG-evolution on the level of matrix elements, in no-core shell model calculations of light nuclei, and in Hartree-Fock calculations up to ${}^{208}\mathrm{Pb}$. Both interactions exhibit very similar convergence properties in light nuclei but show a different systematic behavior as function of particle number.

High-spin states in the doubly magic $N=Z$ nucleus ${}^{56}\mathrm{Ni}$ have been investigated with three fusion-evaporation reaction experiments. New γ-ray transitions are added, and a confirmation of a previously suggested prompt proton decay from a rotational band in ${}^{56}\mathrm{Ni}$ into the ground state of ${}^{55}\mathrm{Co}$ is presented. The rotational bands in ${}^{56}\mathrm{Ni}$ are discussed within the framework of cranked Nilsson-Strutinsky calculations.