We study the possible existence of deconfined quark matter in the interior of neutron stars using the Nambu–Jona-Lasinio model to describe the quark phase. We find that typical neutron stars with masses around 1.4 solar masses do not possess any deconfined quark matter in their center. This can be traced back to the property of the NJL model which suggests a large constituent strange quark mass over a wide range of densities.

The decay of ${}^{96}{\mathrm{Tc}}^g$ has been studied using low-temperature nuclear orientation. Multipole mixing ratios have been deduced for several transitions in the daughter nucleus ${}^{96}\mathrm{Mo}$ by measuring γ-ray anisotropies following the decay of the oriented ${}^{96}\mathrm{Tc}$ nuclei. These new mixing ratios are compared with those determined from previous measurements in light of the possible presence of a low-energy $6^{+}$ mixed-symmetry state in ${}^{96}\mathrm{Mo}.$

We continue our studies of a relativistic quark model that includes a covariant model of confinement. [In the absence of the confinement model, our model reduces to the SU(3)-flavor version of the Nambu–Jona-Lasinio (NJL) model.] In previous works we have studied the radial excitations of the pion, $\eta -{\eta }^{\prime }$ mixing, and ω-φ mixing. Here we extend our work to study the K mesons of the pseudoscalar, vector, and scalar nonets. In addition, we provide some preliminary analysis of the ${}^3{P}_1$ and ${}^1{P}_1$ axial-vector nonets and develop a formalism that enables us to consider ${}^3{P}_1{-}^1{P}_1$ mixing of the strange axial-vector mesons. That is accomplished by adding interactions to the NJL Lagrangian that contain gradients of the quark field. Once the parameters of the model are fixed by fitting the energies of the ω(782), ω(1420), $K\left(495\right),$ and φ(1020), we find the model has significant predictive power. For example, the masses of the $K^{*}\mathrm{}\left(892\right),$ $K_0^{*}\mathrm{}\left(1430\right),$ and $a_1\mathrm{}\left(1260\right)\mathrm{}$ are predicted correctly. For the pseudoscalar nonet we find nineteen states below 2 GeV and for the vector nonet we have eleven states with mass less than 2 GeV. On the whole, the pattern of radial excitations of the various mesons is reproduced in our model.

The importance of core contributions to the anapole moment in nuclei is examined. A model of the core-polarization correction is presented. The model is based on the coupling of the valence particles to the spin-dipole ${J=1\mathrm{}}^{-}$ giant resonances of the core. A shell-model calculation of this correction is presented. The single-particle moments are calculated with Woods-Saxon and Skyrme Hartree-Fock radial wave functions, and the general issues associated with nuclear configuration mixing are discussed.

Asymmetries for the $({\pi }^{-},{\pi }^0)$ reaction on polarized ${}^3\mathrm{He}$ were measured using a 200-MeV pion beam at LAMPF. The ${\pi }^0$’s were detected with the neutral meson spectrometer in coincidence with the recoiling tritons. A recoil triton detector, consisting of scintillation-counter telescopes and a wire chamber, was used to measure the time-of-flight, energy loss, and direction of the tritons. The polarized gaseous ${}^3\mathrm{He}$ target, developed at TRIUMF, was modified to run with two diode lasers; the polarization reached 65%. The asymmetries between ${\theta }_{\mathrm{lab}}=60\mathrm{}°$ and $105°$ were found to be strongly angle dependent. The results are compared with theoretical calculations.

Proton-neutron $\mathrm{}(p-n)\mathrm{}$ interactions and their various aspects in $N\approx Z$ nuclei of $g_{9/2}$ and $f_{7/2}$ subshells are studied using a schematic model interaction with four force parameters proposed recently. It is shown that the model interaction reproduces well observed physical quantities: the double differences of binding energies, symmetry energy, Wigner energy, odd-even mass difference, and separation energy, which testifies to the reliability of the model interaction and its $p-n$ interactions. First of all, the double differences of binding energies are used for probing the $p-n$ interactions. The analysis reveals different contributions of the isoscalar and isovector $p-n$ pairing interactions to two types of double differences of binding energies, and also indicates the importance of a unique form of isoscalar $p-n$ pairing force with all J components. Next, it is shown that this p-n force is closely related to the symmetry energy and the Wigner energy. Other calculations demonstrate the significant roles of $p-n$ interactions in the odd-even mass difference and in the separation energy at $N=Z$.

The relative yields of high energy deuterons and tritons as compared to protons have been measured in $p+\mathrm{Kr},$ ${}^{16}\mathrm{O}+\mathrm{Kr}$ and ${}^{20}\mathrm{Ne}+\mathrm{Ar}$ reactions with a continuously varying beam energy up to $500A\mathrm{}\left(400A\right)\mathrm{}\hspace{0.5em}\mathrm{MeV}.$ Statistical (expanding) evaporation models are not able to reproduce these $d/p$ or $t/p$ ratios, which for high particle energy $(>\mathrm{}30\mathrm{}\hspace{0.5em}\mathrm{MeV})$ increase smoothly with beam energy. Models that contain nucleon-nucleon scattering, like cascade or nuclear molecular dynamics models, can only reproduce the ratios if a final-state interaction is introduced via the coalescence prescription. The coalescence radius that best fit the data is rather constant over wide beam energy intervals. Entropy can, however, not be directly determined from these ratios.

The distorted one-body mixed density matrix, which is the basic nuclear quantity appearing in the definition of the cross section for the semi-inclusive ${A(e,e}^{\prime }p)X$ processes, is calculated within a linked cluster expansion based upon correlated wave functions and the Glauber multiple scattering theory to take into account the final state interaction of the ejected nucleon. The nuclear transparency for ${}^{16}\mathrm{O}$ and ${}^{40}\mathrm{Ca}$ is calculated using realistic central and noncentral correlations and the important role played by the latter is illustrated.

High precision measurements of kaonic hydrogen x rays and also, for the first time, of kaonic deuterium are under way within the DEAR project using the $e^{+}{e}^{-}$ storage ring at Frascati. The values of the strong interaction $1s$ level shift and width in kaonic deuterium cannot be simply predicted by relating them, via the Deser-Trueman formula, to the $K^{-}d$ scattering length because the latter is not known experimentally: it cannot be obtained by adding the $K^{-}p$ and $K^{-}n$ scattering lengths but involves the solution of a complicated multichannel three-body problem. We give results of calculations of the kaonic deuterium strong interaction shift and width using an $(N\overline{K},Y\pi )$ interaction $(Y=\Lambda ,\Sigma )$ that fits the available low-energy scattering data. The $1s$ level shift in kaonic deuterium comes out negative and both the shift and the width are estimated to be about 1 keV. The $2p$ capture rate is estimated to be smaller than the $2\overrightarrow{p}1s$ x-ray transition rate. This information is of importance for the planned experiment as it indicates that most of the kaons should reach the lowest $1s$ level.

The phenomenon of shape coexistence is discussed within the self-consistent Hartree-Fock method and the nuclear shell model. The occurrence of the coexisting configurations with different intrinsic shapes is traced back to the properties of the effective Hamiltonian.

The decays ${}^{110}\mathrm{Rh}$ and ${}^{112}\mathrm{Rh}$ have been investigated using on-line mass separation with the ion-guide technique. Extended decay schemes have been constructed for both the low- and high-spin states in ${}^{112}\mathrm{Rh}$. Mixing ratios for the collective transitions from the $2_2^{+}$ and $3_1^{+}$ states in ${}^{112}\mathrm{Pd}$ have been measured by $\gamma -\gamma$ angular correlation. The presence of two sets of $0^{+}$ and $2^{+}$ states in the 1.1–1.4 MeV range suggests the existence of an intruder band, the energy of which is the lowest in ${}^{110}\mathrm{Pd}$ with two neutrons fewer than the midshell. The quasiparticle levels at 2195 and 2755 keV are assigned $I=4\mathrm{}$ and $I=5\mathrm{}$, respectively. The corresponding levels in ${}^{110}\mathrm{Pd}$ are a new level at 2261 keV and the 2805 keV level. Systematics of log$\mathrm{ft}$ values and excitation energies of these quasiparticle levels is remarkably smooth. The strong $\beta$ feeding to the $I=5\mathrm{}$ quasiparticle state can be regarded as similar to the main branch in the decay of odd Rh isotopes, while a neutron is a spectator.

An algorithm for generating Bose-Einstein momentum space correlations in the particle distributions of simulated relativistic heavy-ion collision events is extended for applications to experiments at the Relativistic Heavy Ion Collider. Quality fits to the momentum space correlations for spherical and nonspherical source geometries are obtained for both the like charged pion $\left[\right({\pi }^{+}{\pi }^{+})$ and $\left({\pi }^{-}{\pi }^{-}\right)]$ and unlike charged pion $\left({\pi }^{+}{\pi }^{-}\right)$ two-body distributions predicted for $200A$ GeV Au+Au central collisions. The momentum space correlations not directly constrained in the fitting algorithm are examined, and strong correlations are found for both the like and unlike charged pion spectra indicating that the correlation signals generated by the algorithm are robust. The model is well suited for the simulation needs of present and future heavy-ion experiments.

We study the photoproduction of scalar mesons close to the threshold of $f_0\mathrm{}\left(980\right)\mathrm{}$ and $a_0\mathrm{}\left(980\right)\mathrm{}$ using a unitary chiral model. Peaks for both resonances show up in the invariant mass distributions of pairs of pseudoscalar mesons. A discussion is made on the photoproduction of these resonances in nuclei, which can shed light on their nature, a subject of continuous debate.

Low spin states in the odd-odd nucleus ${}^{46}\mathrm{V}$ were investigated with the ${}^{46}{\mathrm{T}\mathrm{i}(\mathrm{p},\mathrm{n}\mathrm{\gamma })}^{46}\mathrm{V}$ fusion reaction at the FN-TANDEM accelerator in Cologne. Complementary spectroscopic measurements were done, namely: γ-angular distributions, excitation functions, γγ-coincidences, and γγ-angular correlations. 28 states were observed, 19 for the first time. We evaluated seven new spin assignments and eight new multipole mixing ratios. In particular, the lowest $T=0,$ $J=1\mathrm{}$ quasideuteron state was identified as the 993 keV level. The data compare well to shell model calculations with the KB3 and the FPD6 forces in the full pf shell.

It is pointed out that the study of Gamow-Teller ${\beta }^{+}$ decays of highly deformed $Z\approx N$ nuclei close to the proton drip line is very valuable, especially if $\log \mathrm{ft}$ values of the ${\beta }^{+}$ decays to the ground and low-lying states can be measured with good accuracy. Desirable candidates for this purpose are the ${\beta }^{+}$ decay of ${}_{38}^{76}{\mathrm{Sr}}_{38}$ and ${}_{38}^{75}{\mathrm{Sr}}_{37}.$ The possible absence of an appreciable amount of the Gamow-Teller strength of $\Delta K=0\mathrm{}$ ${\beta }^{+}$ decay of the nucleus ${}_{38}^{76}{\mathrm{Sr}}_{38}$ may be used as a measure of large deformation with strong neutron-proton pair correlation.

The leading contribution to the three-pion-exchange nucleon-nucleon potential is calculated in the framework of chiral symmetry. It has pseudoscalar and axial components and is dominated by the former, which has a range of about 1.5 fm and tends to enhance the one-pion-exchange potential. The strength of this force does not depend on the pion mass, and hence it survives in the chiral limit.

The high-spin structure of ${}^{104}\mathrm{Cd}$ has been studied through the ${}^{50}\mathrm{Cr}{(}^{58}\mathrm{Ni},4p)$ reaction at a beam energy of 220 MeV. The level scheme has been extended up to an excitation energy of 11.9 MeV. Four collective structures have been identified based on two-quasineutron configurations. The low-lying states of both parities, as well as the main $\Delta I=2\mathrm{}$ regular structures observed at high spin, are described in the framework of the interacting boson-fermion model with broken pairs.

Positive-parity high-spin states in the odd-proton nuclei ${}^{83}\mathrm{Rb}$ and ${}^{85}\mathrm{Y}$ have been populated via the ${}^{68}\mathrm{Zn}{(}^{18}\mathrm{O},p2n)$ reaction at 56 MeV and the ${}^{59}\mathrm{Co}{(}^{28}\mathrm{Si},2p)$ reaction at 99 MeV up to ${(37/2\mathrm{}}^{+})$ and ${(33/2\mathrm{}}^{+}),$ respectively. In both nuclei band crossings have been observed at a spin of $21/2$ and interpreted as resulting from the alignment of a $g_{9/2}$ neutron pair, as in other odd-proton nuclei with 46 neutrons. In the three-quasiparticle high-spin excitations, the observed signature splitting and total Routhian surface calculations indicate that the ${}^{83}\mathrm{Rb}$ nucleus exhibits a well-deformed near-oblate shape. No second alignment has been observed in the yrast sequence of ${}^{83}\mathrm{Rb}$ up to a rotational frequency of 0.95 MeV, indicating that for $Z=37\mathrm{}$ and an oblate shape the breaking of a $g_{9/2}$ proton pair is energetically expensive.

Using the self-consistent Thomas-Fermi model from our earlier work, backed by the liquid-drop-model scaling rule for fission barriers, we have constructed a simple algebraic equation for Thomas-Fermi fission barriers. The equation is accurate for proton numbers greater than about 70 and for neutron numbers up to at least 20 units on either side of beta stability. This has made it possible to make a comprehensive comparison of the Thomas-Fermi theory with 120 measured fission barriers.

The $E2\mathrm{}$ and $M1\mathrm{}$ components of the ${}^{16}\mathrm{O}(p,\gamma {)}^{17}\mathrm{F}$ and ${}^7\mathrm{Be}(p,\gamma {)}^8\mathrm{B}$ cross sections, which are involved in the analysis of Coulomb breakup data, are studied in a microscopic model. These investigations provide examples of unusual S factor low-energy dependences.