The mirror ${\beta }^{+}$ decay of ${}^{61}\mathrm{Ga}$ was investigated by means of $\beta$- and $\gamma$-ray spectrometry at the ISOLDE-PSB facility using laser ionization and mass separation. The results for the ${}^{61}\mathrm{Ga}$ half-life and the $Q_{\mathrm{EC}}$ value are 168(3) ms and 9255(50) keV, respectively. The β-decay strength to the ground and low-lying excited states of the daughter ${}^{61}\mathrm{Zn}$ was deduced. The experimental results are in a good agreement with large-scale shell-model calculations.

In a recent experimental study [Gómez del Campo et al., Phys. Rev. Lett. 26, 43 (2001)] of the reaction ${}^{17}\mathrm{F}{\mathrm{}(p,2p)\mathrm{}}^{16}\mathrm{O}$ two-proton events were measured from excitations near a $1^{-},$ $E^{*}=6.15\mathrm{}\hspace{0.5em}\mathrm{MeV}$ state in ${}^{18}\mathrm{Ne}.$ We calculate the resonant two-proton production cross section and branching ratios by means of R-matrix theory. We conclude that it is unlikely that two-proton production via population of the $1^{-}$ state is sufficient to explain the observed two-proton events. Alternative sources of such events are discussed.

Complete sets of analyzing powers have been obtained for a large number of inelastic scattering and single-nucleon stripping channels for 34-MeV polarized ${}^7\mathrm{Li}{+}^{12}\mathrm{C}.$ We present data for inelastic excitation to the 0.478-MeV ${1/2}^{-}$ state of ${}^7\mathrm{Li},$ the 4.44-MeV $2^{+},$ 7.65-MeV $0^{+},$ and 9.64-MeV $3^{-}$ states of ${}^{12}\mathrm{C}$ and for mutual excitation of the ${1/2}^{-}$ and $2^{+}$ states, single-neutron stripping to the 0.0-MeV ${1/2}^{-},$ 3.09-MeV ${1/2}^{+},$ and 3.85-MeV ${5/2}^{+}$ states and an unresolved multiplet centered at 7.6 MeV of ${}^{13}\mathrm{C},$ and single-proton stripping to the 0.0-MeV ${1/2}^{-}$ state and an unresolved doublet of the 3.51-MeV ${3/2}^{-}$ and 3.55-MeV ${5/2}^{+}$ states of ${}^{13}\mathrm{N}.$ These data are analyzed with the continuum-discretized-coupled-channels approach using cluster-folding model form factors in a calculation that includes all the known physics for these systems.

A coherent state of pions is introduced to the nonrelativistic quark model. The coherent pair approximation is employed for the pion field in order to maintain the spin-isospin symmetry. In this approximation the pion is localized in the momentum space, and the vertex form factor in the pion-quark interaction is derived from this localization. The nucleon masses and wave functions are calculated using this model, and our results are compared to those of the quark model with the one pion exchange potential. Similar result is obtained for the mass spectrum, but there exists a clear difference in the internal structure of nucleon resonances.

Nuclear anapole moments are parity-odd, time-reversal-even $E1\mathrm{}$ moments of the electromagnetic current operator. Although the existence of this moment was recognized theoretically soon after the discovery of parity nonconservation (PNC), its experimental isolation was achieved only recently, when a new level of precision was reached in a measurement of the hyperfine dependence of atomic PNC in ${}^{133}\mathrm{Cs}.$ An important anapole moment bound in ${}^{205}\mathrm{Tl}$ also exists. In this paper, we present the details of the first calculation of these anapole moments in the framework commonly used in other studies of hadronic PNC, a meson-exchange potential that includes long-range pion exchange and enough degrees of freedom to describe the five independent $S-P$ amplitudes induced by short-range interactions. The resulting contributions of $\pi ,$ $\rho ,$ and $\omega$ exchange to the single-nucleon anapole moment, to parity admixtures in the nuclear ground state, and to PNC exchange currents are evaluated, using configuration-mixed shell-model wave functions. The experimental anapole moment constraints on the PNC meson-nucleon coupling constants are derived and compared with those from other tests of the hadronic weak interaction. While the bounds obtained from the anapole moment results are consistent with the broad “reasonable ranges” defined by theory, they are not in good agreement with the constraints from the other experiments. We explore possible explanations for the discrepancy and comment on the potential importance of new experiments.

We analyze partially conserved axial current in the nonlinear realization of chiral symmetry in nuclear physics. We construct the two-nucleon (meson-exchange) axial currents and associated pion emission and absorption operators and compare them with those derived earlier in the linear $\sigma$ model. We show the absence of necessity of meson-exchange currents in the nonlinear model, in contrast with the linear one.

We present the result of a theoretical study of the quasifree electrofission of ${}^{238}\mathrm{U}.$ The exclusive differential cross sections for the quasifree scattering reaction stage have been calculated in plane wave impulse approximation, using a macroscopic-microscopic approach for the description of the proton bound states. The nuclear shape was parametrized in terms of Cassinian ovoids. The equilibrium deformation parameters have been calculated by minimizing the total nuclear energy. In the calculation the axially deformed Woods-Saxon single-particle potential was used. The obtained single-particle momentum distributions were averaged over the nuclear symmetry axis direction. The occupation numbers were calculated in the BCS approach. The fissility for the single-hole excited states of the residual nucleus ${}^{237}\mathrm{Pa}$ was calculated on the statistical theory grounds, both without taking into account the preequilibrium emission of the particle and with preequilibrium emission in the framework of the exciton model.

The strangeness content of hadronic matter is studied in a string-flip model that reproduces various aspects of the QCD-inspired phenomenology, such as quark clustering at low density and color deconfinement at high density, while avoiding long range van der Waals forces. Hadronic matter is modeled in terms of its quark constituents by taking into account its internal flavor $\mathrm{}(u,d,s)\mathrm{}$ and color (red, blue, green) degrees of freedom. Variational Monte Carlo simulations in three spatial dimensions are performed for the ground-state energy of the system. The onset of the transition to strange matter is found to be influenced by weak, yet not negligible, clustering correlations. The phase diagram of the system displays an interesting structure containing both continuous and discontinuous phase transitions. Strange matter is found to be absolutely stable in the model.

In this work we investigate the effects of different equations of state (EOS) in explaining high density matter properties. We study not only β stable states, pure neutron, and symmetric matter, but also states with different proton fractions. We show that the influence of the parametrization is already felt at not so dense matter while the importance of the hyperon to meson coupling only appears at densities much larger than the nuclear matter saturation density. We have also checked the effects of considering a hyperon to meson coupling larger than the universal coupling. Neutron star properties are obtained with the EOS discussed in the present work.

The quark-delocalization, color-screening model, extended by inclusion of a one-pion-exchange (OPE) tail, is applied to the study of the deuteron and the $d^{*}$ dibaryon. The results show that the properties of the deuteron (an extended object) are well reproduced, greatly improving the agreement with experimental data as compared to our previous study (without OPE). At the same time, the mass and decay width of the $d^{*}$ (a compact object) are, as expected, not altered significantly.

The one-phonon mixed-symmetry $2_{1,\mathrm{ms}}^{+}$ state and two-phonon mixed-symmetry $3_{1,\mathrm{ms}}^{+}$ and $2_{2,\mathrm{ms}}^{+}$ states have been identified in ${}^{96}\mathrm{Ru}$ based on intensity branching ratios, $E2/M1\mathrm{}$ multipole mixing ratios, upper lifetime limits, and a comparison with the experimental data for ${}^{94}\mathrm{Mo}.$ The observables were obtained from Doppler-shift attenuation measurements and $\gamma \gamma$ angular correlation analyses following the ${}^{95}\mathrm{Mo}{(}^3\mathrm{He}{,2n)}^{96}\mathrm{Ru}$ reaction and the ${\beta }^{+}$ decay of ${}^{96}\mathrm{Rh}.$ Shell-model calculations performed for ${}^{96}\mathrm{Ru}$ give clear support for the interacting boson model 2 mixed-symmetry assignments of the one-phonon $2_3^{+}$ state at 2283.8 keV as well as of the two-phonon $2_5^{+}$ state at 2739.8 keV and $3_2^{+}$ state at 2897.7 keV.

The phenomenom of emerging regular spectral features from random interactions is addressed in the context of the vibron model. A mean-field analysis links different regions of the parameter space with definite geometric shapes. The results that are, to a large extent, obtained in closed analytic form provide a clear and transparent interpretation of the high degree of order that has been observed in numerical studies.

An assessment of the magnitude of the rearrangement contribution to the Fermi energy and to the binding energy per particle is carried out in symmetric nuclear matter by extending the G-matrix framework. The restoration of the thermodynamic consistency or, equivalently, the fulfillment of the Hugenholtz–Van Hove theorem, is discussed.

The level densities and $\gamma$-strength functions of the weakly deformed ${}^{148}\mathrm{Sm}$ and ${}^{149}\mathrm{Sm}$ nuclei have been extracted. The temperature versus excitation energy curve, derived within the framework of the microcanonical ensemble, shows structures, which we associate with the breakup of Cooper pairs. The nuclear heat capacity is deduced within the framework of both the microcanonical and canonical ensembles. We observe negative heat capacity in the microcanonical ensemble whereas the canonical heat capacity exhibits an S shape as a function of temperature, both signals of a phase transition. The structures in the $\gamma$-strength functions are discussed in terms of the pygmy resonance and the scissors mode built on excited states. The samarium results are compared with data for the well-deformed ${}^{161,162}\mathrm{Dy},$ ${}^{166,167}\mathrm{Er},$ and ${}^{171,172}\mathrm{Yb}$ isotopes and with data from $(n,\gamma )$ experiments and giant dipole resonance studies.

The importance of quantum effects for exotic nuclear shapes is discussed. Based on an example of a sheet of nuclear matter of infinite lateral dimensions but finite thickness, it is shown that the quantization of states in momentum space, resulting from the confinement of the nucleonic motion in the conjugate geometrical space, generates a pressure resisting such a confinement and, consequently, restoring forces driving the systems toward compact geometries. In the liquid-drop model, these quantum effects are implicitly included in the surface energy term, via a choice of interaction parameters, an approximation that has been found valid for compact shapes, but has not yet been scrutinized for exotic shapes.

We present a formalism to extract the dynamical nucleon polarizabilities defined via a multipole expansion of the structure amplitudes in nucleon Compton scattering. In contradistinction to the static polarizabilities, dynamical polarizabilities gauge the response of the internal degrees of freedom of a composed object to an external, real photon field of arbitrary energy. Being energy dependent, they therefore contain additional information about dispersive effects induced by internal relaxation mechanisms, baryonic resonances, and meson production thresholds of the nucleon. We give explicit formulae to extract the dynamical electric and magnetic dipole as well as quadrupole polarizabilities from low-energy nucleon Compton scattering up to the one-pion production threshold, and discuss the connection to the definition of static nucleon polarizabilities. As a concrete example, we examine the results of leading order heavy baryon chiral perturbation theory for the four leading spin-independent isoscalar polarizabilities of the nucleon. Finally, we consider the possible role of energy-dependent effects in low-energy extractions of the isoscalar dipole polarizabilities from Compton scattering on the deuteron.

The formation of Cooper pairs resulting from the exchange of vibrations between pairs of fermions moving in time reversal states close to the Fermi surface in a semi-infinite system of nuclear matter (slab model) with parameters adjusted so as to mimic real nuclei, leads to pairing gaps which account for a substantial fraction of the experimental value throughout the mass table. The predictions are in qualitative agreement with detailed calculations carried out for finite nuclei and testify to the central role the surface of nuclei plays in the phenomenon of nuclear superfluidity.

Precise elastic scattering differential cross sections have been measured for the ${}^{12}\mathrm{C}{+}^{58}\mathrm{Ni}{,}^{208}\mathrm{Pb}$ systems at sub-barrier energies. The corresponding bare potentials have been determined at interaction distances larger than the respective barrier radii, and the results have been compared with those from an early extensive systematics for the nuclear potential. The present data have been combined with others for the ${}^{12}\mathrm{C}{+}^{12}\mathrm{C}{,}^{208}\mathrm{Pb}$ systems at intermediate energies, in order to extract the ${}^{12}\mathrm{C}$ ground-state nuclear density through an unfolding method.

Isotopic effects observed in fragmentation reactions induced by protons, deuterons, and $\alpha$ particles of incident energies between 660 MeV and 15.3 GeV on ${}^{112}\mathrm{Sn}$ and ${}^{124}\mathrm{Sn}$ targets are discussed. The exponential scaling of the yield ratios with the third component of the fragment isospin $t_3=\left(N-Z\right)/2\mathrm{}$ is observed in all reactions, with scaling parameters that depend on the incident energy. Breakup temperatures for these reactions are deduced from double ratios of isotopic yields and tested for their relation with the isoscaling parameters. The quantum-statistical and the statistical multifragmentation (SMM) models are used for interpreting the results. The observed isoscaling can be understood as a consequence of the statistical origin of the emitted fragments in these reactions. The SMM analysis shows that the exponent describing the isoscaling behavior is proportional to the strength of the symmetry term of the fragment binding energy. Using this result, a symmetry-term coefficient $\gamma \approx 22.5\mathrm{MeV}$ for fragments at breakup is deduced from the experimental data. This is close to the standard value and supports SMM assumptions for the breakup configuration. An alternative method of determining the symmetry-energy coefficient, by using isotope distribution widths, is also discussed.

There is a very large body of literature in which the Nambu–Jona-Lasino (NJL) model has been applied in the study of mesons, baryons, and hadronic matter. One area of interest has been the calculation of corrections of order ${1/N}_c$ to various quantities calculated in the leading (Hartree) approximation. Of particular interest is the work of Dmitrašinović, Schulze, Tegen, and Lemmer [Ann. Phys. (N.Y.) 238, 332 (1995)]. These authors have considered the SU(2)-flavor NJL model and identified a set of diagrams, whose calculation yields ${1/N}_c$ corrections, while at the same time maintaining the relations, such as the Goldberger-Treiman relation, that follow from the chiral symmetry of the theory. In the present work we extend the work of Dmitrašinović et al. to the case of SU(3)-flavor symmetry. In particular, we consider ${1/N}_c$ corrections to the quark vacuum condensates and to the “gap equation.” While ${1/N}_c$ corrections to the pion decay constant are significant, the corrections to the condensates are found to be quite small, as was the case in the SU(2)-flavor analysis. The Pauli-Villars regularization procedure is thought to be particularly useful for such calculations, since that procedure is known to maintain the symmetries of the theory. As part of our analysis we extend the Pauli-Villars regularization procedure to the case in which a particular diagram contains quarks of different constituent mass. Such diagrams appear when we generalize the SU(2)-flavor analysis to SU(3). We also show that, if we use the “textbook” definition of the Pauli-Villars method, in which fictitious particles of large mass are added to the theory, the resulting formalism may not be used in the case of the NJL model. What is done in practice is that particular divergent (and nondivergent) integrals are regulated in a fashion that yields results that are quite similar to the results of the covariant regularization procedure that is used by many authors. For constituent quark mass values of the magnitude usually used in the case of the SU(3)-flavor NJL model, we find that the ${1/N}_c$ corrections in the calculation of the pion decay constant play a role in obtaining satisfactory values for the quark vacuum condensates and the strength of the ’t Hooft interaction.