The ground state and low-lying levels of the unbound ${}^{11}\mathrm{N}$ nucleus were investigated with the three-neutron pickup reaction ${}^{14}\mathrm{N}{(}^3\mathrm{He}{,}^6\mathrm{He}{)}^{11}\mathrm{N}.$ The energies and widths of these, experimentally observed, levels are compared with other measurements and calculations. Angular distributions were measured for the first time for this reaction. The distorted-wave Born approximation analysis confirms the spin assignments for the lowest levels.

Fragments from the breakup of 32 MeV/nucleon ${}^{20}\mathrm{Na},$ ${}^{20}\mathrm{Ne},$ and ${}^{20}\mathrm{F}$ projectile nuclei were measured with isotopic resolution using the FAUST detector array. Complete reconstruction of the fragmenting source was performed on an event-by-event basis. Events analyzed in this study were restricted to those with a summed fragment charge equal to the beam in which all fragments were isotopically identified. The change in neutron content of the projectile could be inferred from the complete isotopic reconstruction of the quasiprojectile. The $〈N/Z〉$ present in the fragmenting source is not equal to the $N/Z$ of the initial beam; there has been a shift toward the valley of stability. Additionally, there is now a distribution in the $N/Z$ of the fragmenting system. Multineutron transfer from the neutron-rich target was observed for proton-rich projectiles.

The intensity of positron annihilation radiation emitted by a sample of natural chromium trioxide, ${\mathrm{CrO}}_3,$ containing 4.7 g of ${}^{50}\mathrm{Cr},$ was measured for 30 days. The background was measured with samples of iron, copper, and no sample at all (air), during a similar period of time. From the net intensity of the 511-keV line in the HpGe coincidence spectrum the partial half-life for the positron-electron capture double beta decay of ${}^{50}\mathrm{Cr},$ $T_{1/2}({\beta }^{+}EC,2\mathrm{}\nu +0\mathrm{}\nu )=1.3\mathrm{}\left(12\right)\mathrm{}\times {10}^{18}\mathrm{yr}$ at the 95% CL was deduced. Alternatively, at 95% CL the effect may be considered absent, the resulting lower limit for this half-life of $1.3\times {10}^{18}\mathrm{yr}$ now representing an order of magnitude improvement over the existing result.

The cross sections of the ${}^8\mathrm{Li}(n,\gamma {)}^9\mathrm{Li}$ and ${}^8\mathrm{B}(p,\gamma {)}^9\mathrm{C}$ capture reactions have been analyzed using the direct capture model. At low energies, which are the astrophysically relevant regions, the capture process is dominated by $E1\mathrm{}$ transitions from incoming s waves to bound p states. The cross sections of both mirror reactions can be described simultaneously with consistent potential parameters, whereas previous calculations have overestimated the capture cross sections significantly. However, the parameters of the potential have to be chosen very carefully because the calculated cross section of the ${}^8\mathrm{Li}(n,\gamma {)}^9\mathrm{Li}$ reaction depends sensitively on the potential strength.

A transport approach including a leakage effect for $J/\psi$’s in the transverse phase space is used to calculate the ratios between the $J/\psi$ transverse momentum distributions in several centrality bins for Pb-Pb collisions at $E/A=160\mathrm{}\mathrm{GeV}.$ From the comparison with the CERN-SPS data, where the centrality is characterized by the transverse energy $E_t,$ the leakage effect is extremely important in the region of high transverse momentum and high transverse energy, and both the threshold and the comover models can describe the ratio well for all centrality bins except the most central one ${(E}_t<100\mathrm{}\mathrm{GeV}),$ for which the comover model calculation is considerably better than the threshold one.

Nonanalog Fermi and Gamow-Teller branches in the superallowed β decay of ${}^{74}\mathrm{Rb}$ have been investigated using γ-ray and conversion-electron spectroscopy. Nine observed transitions, in conjunction with a recent shell model calculation, determine the branching ratio of the analog transition to be 99.5(1)%. The experimental upper limits for the Fermi decay to the $0_2^{+}$ and ${(0\mathrm{}}_3^{+})$ levels are in agreement with recent theoretical predictions. The $Q_{\mathrm{EC}}$ value for the ${}^{74}\mathrm{Rb}$ β decay is predicted to be 10405(9) keV.

The wave function of the second $0^{+}$ state of ${}^{12}\mathrm{C},$ which was obtained a long time ago by solving the microscopic $3\alpha$ problem, is shown to be almost completely equivalent to the wave function of the $3\alpha$ condensed state, which has been proposed recently by the present authors. This equivalence of the wave functions is shown to hold in two cases where different effective two-nucleon forces are adopted. This finding gives strong support for interpreting the second $0^{+}$ state of ${}^{12}\mathrm{C},$ which is the key state for the synthesis of ${}^{12}\mathrm{C}$ in stars (“Hoyle” state), and which is one of the typical mysterious $0^{+}$ states in light nuclei, as a gaslike structure of three $\alpha$ particles, Bose condensed into an identical s-wave function.

The neutron-deficient nucleus ${}^{66}\mathrm{Ge}$ was populated at high spin in two experiments using the reaction ${}^{40}\mathrm{Ca}{(}^{32}\mathrm{S},\alpha 2p)$ at beam energies of 105 and 95 MeV. In the first experiment, a self-supporting ${}^{40}\mathrm{Ca}$ target was used, while a gold-backed target of similar thickness was used in the second experiment. $\gamma$ rays were detected with the EUROBALL array, combined with the charged-particle detector array EUCLIDES and the Neutron Wall. The level scheme of ${}^{66}\mathrm{Ge}$ was extended up to $E\approx 18\mathrm{MeV}$ and $I^{\pi }{=(23\mathrm{}}^{-}).\mathrm{}$ Above angular momentum ${10}^{+},$ we found two sequences, connected by energetically staggered $\Delta I=1\mathrm{}\hspace{0.5em}M1\mathrm{}$ transitions. The total Routhian surface calculations describe ${}^{66}\mathrm{Ge}$ at lower spins as a $\gamma$-soft nucleus having a moderate deformation of ${\beta }_2\approx 0.23,$ while a triaxial deformation is predicted for the band structures above $I^{\pi }{=10\mathrm{}}^{+}.$ To our knowledge, this is the first observation of staggered $M1\mathrm{}$ transitions in a deformed four-quasiparticle $\pi {(g}_{9/2}^2\left)\nu {(g}_{9/2}^2\right)$ structure.

Cross sections and analyzing powers for the ${}^{11}\mathrm{B}\left(\overrightarrow{p}{,p}^{\prime }\right)$ reaction have been measured using a 150-MeV polarized proton beam from the AGOR cyclotron at KVI. For the stronger inelastic transitions, also spin-flip probabilities have been extracted. To predict cross sections and spin observables a microscopic (coordinate space) model of elastic scattering has been used, whereas for inelastic scattering calculations were performed in the distorted-wave approximation. In the model calculations a medium-modified two-nucleon effective interaction was used and nuclear structure information was obtained from shell-model calculations in a complete $\mathrm{}(0+2)\mathrm{}ħ\omega$ model space for parity-conserving transitions and a $1ħ\omega$ shell-model description in the case of parity-changing transitions. With the help of these model calculations, spin-isovector parts of the $M1\mathrm{}$ strengths for the negative-parity states at excitation energies of 2.125 MeV ${(J}^{\pi }{=1/2\mathrm{}}^{-}),$ 4.445 MeV ${(J}^{\pi }{=5/2\mathrm{}}^{-}),$ 5.020 MeV ${(J}^{\pi }{=3/2\mathrm{}}^{-}),$ and 8.920 MeV ${(J}^{\pi }{=5/2\mathrm{}}^{-})$ have been extracted and compared to known Gamow-Teller strengths for the analog transitions to ${}^{11}\mathrm{C}.$

The polarization-transfer coefficient $D_{{\mathrm{nn}}^{\prime }}$ in the elastic scattering of 150-MeV protons from ${}^{11}\mathrm{B}$ has been measured in the angular range $5°<{\theta }_{\mathrm{c}.\mathrm{m}.\mathrm{}}<31\mathrm{}°.$ Significant deviations of $D_{{\mathrm{nn}}^{\prime }}$ from unity are observed starting around a center-of-mass scattering angle of $23°.$ The observed angular variation of $D_{{\mathrm{nn}}^{\prime }}$ is analyzed using phenomenological and microscopically generated optical-model potentials to describe the monopole attributes of elastic scattering and to generate the distorted waves used in a distorted-wave approximation evaluation of nonzero multipole contributions to the elastic scattering process. The same approach is used to analyze datasets of $D_{{\mathrm{nn}}^{\prime }}$ in elastic scattering from ${}^{13}\mathrm{C}$ and off ${}^{15}\mathrm{N},$ which are available in the literature. The agreement of the fully microscopic analysis with the data is comparable or, in the case of ${}^{11}\mathrm{B},$ slightly better than what is achieved with conventional phenomenological optical-model calculations.

The intrinsic dynamics of a system with open decay channels is described by a non-Hermitian effective Hamiltonian which at the same time allows one to find the external dynamics—reaction cross sections. We discuss ways of incorporating this approach into the shell model context. The approach is capable of describing a multitude of phenomena in a unified way combining physics of structure and reactions. Self-consistency of calculations for a chain of nuclides and threshold energy dependence of the continuum coupling are crucial for the description of loosely bound states. Schematic and realistic examples of open many-body systems where internal configuration mixing is generated by pairing are presented.

Deformed configuration mixing shell model with isospin projection (DSMT) is applied to study the structure of collective $T=0\mathrm{}$ and $T=1\mathrm{}$ bands in the odd-odd $N=Z$ nuclei ${}^{46}\mathrm{V}$ and ${}^{50}\mathrm{Mn}.$ The $\mathrm{pf}$-shell KB3 interaction is employed in the calculations. The $T=0\mathrm{}$ and $T=1\mathrm{}$ bands in both the nuclei compare well with experiment including the $E2\mathrm{}$ and $M1\mathrm{}$ transition strengths. The DSMT predicted structures of the bands in these nuclei are similar to those in the rotor-plus-quasideuteron model.

A simple model for QCD is presented, which is able to reproduce the meson spectrum at low energy. The model is a Lipkin-type model for quarks coupled to gluons. The basic building blocks are quark-antiquark pairs coupled to a definite flavor and spin. These pairs are coupled to pairs of gluons with spin zero. The multiplicity problem, which dictates that a given experimental state can be described in various manners, is removed when a particle-mixing interaction is turned on. In this first paper of a series we concentrate on the discussion of meson states at low energy, the so-called zero temperature limit of the theory. The treatment of baryonic states is indicated, also.

A schematic model for QCD, developed in a previous paper, is applied to calculate meson properties in the high temperature (up to 0.5 GeV) regime. It is a Lipkin model for quark-antiquark pairs coupled to gluon pairs of spin zero. The partition function is constructed with the obtained meson spectrum and several thermodynamical observables are calculated, such as the energy density, heat capacity, as well as relative production rates of mesons and absolute production rates for pions and kaons. The model predictions show a qualitative agreement with data. Based on these results, we advocate the use of the model as a toy model for QCD.

We propose a simple method to evaluate the lowest energy levels of a given angular momentum using exact Monte Carlo methods. The method relies on an efficient evaluation of quantities such as $〈\psi \mathrm{NZ}|P_{\mathrm{JJ}}^{\mathrm{}\left(J\right)\mathrm{}}Ĥ{\mathrm{e}}^{-\beta Ĥ}|\psi \mathrm{NZ}〉$ where the wave functions are particle number projected Hartree-Fock-Bogoliubov wave functions and $P_{\mathrm{JJ}}^{\mathrm{}\left(J\right)\mathrm{}}$ is the angular momentum projector with $J_z=J.\mathrm{}$ The method has been applied to the evaluation of $0^{+},$ $2^{+},$ $4^{+},$ $6^{+}$ levels of ${}^{166}\mathrm{Er}$ within the $\mathrm{pairing}+\mathrm{quadrupole}$ model and we show that energy eigenvalues can be obtained for small β values.

Supersymmetric or Darboux transformations are used to construct local phase equivalent deep and shallow potentials for $\mathcal{l}\ne 0$ partial waves. We associate the value of the orbital angular momentum with the asymptotic form of the potential at infinity, which allows us to introduce adequate long-distance transformations. The approach is shown to be effective in getting the correct phase shift effective range expansion. Applications are considered for the ${}^1{P}_1$ and ${}^1{D}_2$ partial waves of the neutron-proton scattering.

The rotational bands of ${}^{169,171,173}\mathrm{Lu}$ are studied by deformed Hartree-Fock and angular momentum projection techniques. Energy spectra and other spectroscopic properties (such as matrix elements of electromagnetic operators) are calculated up to high spin values $J=81/2.\mathrm{}$ $B\left(E2\mathrm{}\right)\mathrm{}$ and $B\left(M1\mathrm{}\right)\mathrm{}$ values for all the bands are calculated. Angular momenta carried by nucleons in some of the large j orbits are evaluated for each band, and these are related to the signature splittings, particularly for ${K=1/2\mathrm{}}^{-}$ and ${K=1/2\mathrm{}}^{+}$ bands. Three- and five-quasiparticle bands are also studied. With our model we are able to explain substantially the known spectra and transitions in these nuclei. Besides, we predict many other quantities for future verification; among them are the electric quadrupole and magnetic dipole moments of the bandheads and other states of the bands, excitation energies, and other properties of multi-quasiparticle bands.

The inherent nodal surface structure analysis approach is proposed for six-quark clusters with u, d, and s quarks. The wave functions of the six-quark clusters are classified, and the contribution of the hidden-color channels are discussed. The quantum numbers and configurations of the wave functions of the low-lying dibaryons are obtained. The states $[\Omega \Omega {]}_{{(0,0\mathrm{}}^{+})},$ $[\Omega \Omega {]}_{{(0,2\mathrm{}}^{-})},$ $[{\Xi }^{*}\Omega {]}_{{(1/2,0\mathrm{}}^{+})},$ and $[{\Sigma }^{*}{\Sigma }^{*}{]}_{{(0,4\mathrm{}}^{-})}$ and the hidden-color channel states with the same quantum numbers are proposed to be the candidates of experimentally observable dibaryons.

Associative photoproduction of $\omega$ meson and $N^{*}\mathrm{}\left(1440\right)\mathrm{}$ on nucleons, $\gamma +\overrightarrow{N}\omega {+N}^{*}\mathrm{}\left(1440\right),$ in the near threshold region is investigated in a framework employing effective Lagrangians. Besides $\pi$ exchange in the t channel, baryon exchanges, i.e., N and $N^{*}$ exchanges, in the s and u channels are also taken into account in calculations of differential cross section and beam asymmetry. Important inputs of this model are the vector and tensor coupling constants of $\omega {\mathrm{NN}}^{*}\mathrm{}\left(1440\right)\mathrm{}$ vertex, which are assumed to be equal to the values of these couplings for $\omega \mathrm{NN}$ vertex. Using our previous estimation of $\omega \mathrm{NN}$ coupling constants obtained from a fit to available experimental data on photoproduction of $\omega$ meson in the near threshold region, we produce the necessary numerical predictions for different observables in $\gamma +\overrightarrow{N}\omega {+N}^{*}\mathrm{}\left(1440\right).$ Numerical results show that at low $|t|$ dominant contribution comes from t channel $\pi$ exchange while the effects of nucleon and $N^{*}\mathrm{}\left(1440\right)\mathrm{}$ pole terms can be seen at large $|t|.$ Our predictions for the differential cross section and beam asymmetry for the processes $\gamma +\overrightarrow{N}\omega {+N}^{*}\mathrm{}\left(1440\right),$ where N is proton and neutron, at $E_{\gamma }=2.5\mathrm{}\mathrm{GeV}$ are presented with zero width approximation and also with the inclusion of width effects of $N^{*}\mathrm{}\left(1440\right).$