The effect of one-gluon-exchange (OGE) pair currents on the ratio ${\mu }_p{G}_E^p{/G}_M^p$ for the proton is investigated within a nonrelativistic constituent quark model starting from $\mathrm{SU}\mathrm{}\left(6\right)\mathrm{}\times \mathrm{O}\mathrm{}\left(3\right)\mathrm{}$ nucleon wave functions, but with relativistic corrections. We found that the OGE pair currents are important to reproduce well the ratio ${\mu }_p{G}_E^p{/G}_M^p.$ With the assumption that the gluonic currents are the driving mechanism for the violation of the scaling law, we predict the neutron ratio ${\mu }_n{G}_E^n{/G}_M^n.$

The odd-odd Cs isotopes ${}^{128-134}\mathrm{Cs}$ have been investigated in search of chiral doublet bands. Two nearly degenerate bands built on the $\pi h_{11/2}\otimes \nu h_{11/2}$ configuration have been identified in ${}^{128-132}\mathrm{Cs}.$ Systematics of various experimental observables associated with the partner bands are presented. The ${B\left(M1\mathrm{}\right)\mathrm{}}_{\mathrm{In}}{/B\left(M1\mathrm{}\right)\mathrm{}}_{\mathrm{Out}}$ staggering with spin was discovered to be in phase with the $B\left(M1\mathrm{}\right)/B\left(E2\mathrm{}\right)\mathrm{}$ staggering for the yrast partner band. A core-quasiparticle coupling model employing the Kerman-Klein-Dönau-Frauendorf method was applied to study ${}^{128}\mathrm{Cs}.$ A triaxial core with an irrotational-flow moment of inertia was assumed. The chiral features, as well as previously known experimental characteristics of the $\pi h_{11/2}\otimes \nu h_{11/2}$ yrast partner band, are well reproduced demonstrating the important role played by triaxiality in the underlying physics in these nuclei.

The strong interaction effects of isospin- and spin-dependent nucleon-nucleon correlations observed in many-body calculations are interpreted in terms of a one-pion exchange mechanism. Including such effects in computations of nuclear parity violating effects leads to enhancements of about 10%. A larger effect arises from the one-boson exchange nature of the parity nonconserving nucleon-nucleon interaction, which depends on both weak and strong meson-nucleon coupling constants. Using values of the latter that are constrained by nucleon-nucleon phase shifts leads to enhancements of parity violation by factors close to 2, so that much of previously noticed discrepancies between weak-coupling constants extracted from different experiments can be removed and there is no need to use a very large value of $f_{\pi }$ to explain the ${}^{133}\mathrm{Cs}$ experimental results.

We have performed high-precision measurements of the coherent neutron scattering lengths of gas phase molecular hydrogen and deuterium using neutron interferometry. After correcting for molecular binding and multiple scattering from the molecule, we find $b_{\mathrm{np}}=(-3.7384\pm 0.0020)\mathrm{fm}$ and $b_{\mathrm{nd}}=(6.6649\mathrm{}\pm 0.0040)\mathrm{fm}.$ Our results are in agreement with the world average of previous measurements, $b_{\mathrm{np}}=(-3.7410\pm 0.0010)\mathrm{fm}$ and $b_{\mathrm{nd}}=(6.6727\mathrm{}\pm 0.0045)\mathrm{fm}.$ The new world averages for the $n-p$ and $n-d$ coherent scattering lengths, including our new results, are $b_{\mathrm{np}}=(-3.7405\pm 0.0009)\mathrm{fm}$ and $b_{\mathrm{nd}}=(6.6683\mathrm{}\pm 0.0030)\mathrm{fm}.$ We compare $b_{\mathrm{nd}}$ with the calculations of the doublet and quartet scattering lengths of several nucleon-nucleon potential models and show that almost all known calculations are in disagreement with the precisely measured linear combination corresponding to the coherent scattering length. Combining the world data on $b_{\mathrm{nd}}$ with the modern high-precision theoretical calculations of the quartet $n-d$ scattering lengths recently summarized by Friar et al., we deduce a new value for the doublet scattering length of ${}^2{a}_{\mathrm{nd}}=[0.645\pm 0.003(\mathrm{expt})\pm 0.007(\mathrm{theory}\left)\right]\mathrm{fm}.$ This value is a factor of 4, more precise than the previously accepted value of ${}^2{a}_{\mathrm{nd}}=[0.65\pm 0.04(\mathrm{expt}\left)\right]\mathrm{fm}.$ The current state of knowledge of scattering lengths in the related $p-d$ system, ideas for improving by a factor of 5 the accuracy of the $b_{\mathrm{np}}$ and $b_{\mathrm{nd}}$ measurements using neutron interferometry, and possibilities for further improvement of our knowledge of the coherent neutron scattering lengths of ${}^3\mathrm{H},$ ${}^3\mathrm{He},$ and ${}^4\mathrm{He}$ are discussed.

The Goldstone-Brueckner perturbation theory is extended to incorporate in a simple way correlations associated with large-amplitude collective motions in nuclei. The new energy expansion making use of nonorthogonal vacua still allows to remove the divergences originating from the hard core of the bare interaction. This is done through the definition of a new Brueckner matrix summing generalized Brueckner ladders. At the lowest order, this formalism motivates variational calculations beyond the mean field, such as the generator coordinate method (GCM) and the projected mean-field method, from a perturbative point of view for the first time. Going to higher orders amounts to incorporate diabatic effects in the GCM and to extend the projection technique from product states to well-defined correlated states.

Energies for three positive and three negative parity bands predicted by the extended coherent state model in ${}^{218,226}\mathrm{Ra},$ ${}^{228}\mathrm{Th},$ ${}^{232}\mathrm{Th},$ in four uranium even-mass isotopes, ${}^{232-238}\mathrm{U},$ and in ${}^{238}\mathrm{Pu},$ are calculated and used to point out new signatures for octupole deformation in ground as well as in $\beta$ and $\gamma$ bands. A beat pattern is found by using a new displacement energy function, which is more appropriate for a spectrum that exhibits large deviations from a linear $J(J+1\mathrm{})\mathrm{}$ dependence.

We study Gamow-Teller strength distributions of ${}^{76}\mathrm{Ge}$ and ${}^{76}\mathrm{Se}$ within a deformed quasiparticle random-phase approximation formalism, which includes residual spin-isospin forces in the particle-hole and particle-particle channels. We consider two different methods to construct the quasiparticle basis, a self-consistent approach based on a deformed Hartree-Fock calculation with density-dependent Skyrme forces and a more phenomenological approach based on a deformed Woods-Saxon potential. Both methods contain pairing correlations in the BCS approach. We discuss the sensitivity of Gamow-Teller strength distributions to the deformed mean field and residual interactions.

We calculate the low-lying ${B(E2,0\mathrm{}}_{\mathrm{g}.\mathrm{s}.\mathrm{}}^{+}\to 2_{\mathrm{f}}^{+})$ distribution of strength in ${}^{68}\mathrm{Ni}$ and other nickel isotopes using several theoretical approaches. We find that in ${}^{68}\mathrm{Ni}$ the calculated $B\left(E2\mathrm{}\right)\mathrm{}$ transition to the first $2^{+}$ state exhausts only a fraction of the low-lying $B\left(E2\mathrm{}\right)\mathrm{}$ strength, while the remainder of the low-lying strength is mainly collected in the group of states lying above 4 MeV. This fragmentation is sensitive to the size of the $N=40\mathrm{}$ gap. We argue that the small experimental $B\left(E2\mathrm{}\right)\mathrm{}$ value to the first $2^{+}$ state is not a strong evidence for the double-magic character of ${}^{68}\mathrm{Ni}.$

We investigate the reliability of transition strengths computed in the random-phase approximation (RPA), comparing with exact results from diagonalization in full $0ħ\omega$ shell-model spaces. The RPA and shell-model results are in reasonable agreement for most transitions; however, some very low lying collective transitions, such as isoscalar quadrupole ones, are in serious disagreement. We suggest that the failure lies with incomplete restoration of broken symmetries in the RPA. Furthermore, we prove, analytically and numerically, that standard statements regarding the energy-weighted sum rule in the RPA do not hold if an exact symmetry is broken.

Nuclear liquid-drop model is revisited and an explicit introduction of the surface-curvature terms is presented. The corresponding parameters of the extended classical energy formula are adjusted to the contemporarily known nuclear binding energies and fission-barrier heights. Using 2766 binding energies of nuclei with $Z>~8$ and $N>~8$ it is shown that the performance of the new approach is improved by a factor of about 6, compared to the previously published liquid-drop model results, in terms of the masses (new rms deviation $〈\delta M〉=0.698\mathrm{}\mathrm{MeV})$ and the fission barriers by a factor of about 3.5 (new rms deviation of the fission barriers of isotopes with $Z>\mathrm{}70\mathrm{}$ is $〈\delta V_B〉=0.88\mathrm{}\mathrm{MeV}).\mathrm{}$ The role of the nuclear surface-curvature terms and their effects on the description of the experimental quantities are discussed in detail. For comparison, the parameters of the more “traditional” classical energy expressions are refitted, taking into account the nuclear masses known today and the performances of several variants of the model are compared. The isospin dependence in the new description of the barriers is in a good agreement with the extended Thomas-Fermi approach. It also demonstrates a good qualitative agreement with the fission lifetime systematics tested on the long chain of Fermium isotopes known experimentally. The new approach offers a very high stability in terms of the extrapolation from the narrower range of nuclides to a more extended one—a property of particular interest for the contemporary exotic beam projects: the corresponding properties are illustrated and discussed. The new description of the fission barriers being significantly improved, in particular, the new calculated barriers being lower, flatter, but stiffer against high-multipolarity deformations. The chances for “extra” stabilization of the hyperdeformed minima at high spin increase, thus calling for the new total energy Strutinsky-type calculations.

A relativistic mean-field model is used to study the ground-state properties of neutron-rich nuclei. Nonlinear isoscalar-isovector terms, unconstrained by present day phenomenology, are added to the model Lagrangian in order to modify the poorly known density dependence of the symmetry energy. These new terms soften the symmetry energy and reshape the theoretical neutron drip line without compromising the agreement with existing ground-state information. A strong correlation between the neutron radius of ${}^{208}\mathrm{Pb}$ and the binding energy of valence orbitals is found: the smaller the neutron radius of ${}^{208}\mathrm{Pb},$ the weaker the binding energy of the last occupied neutron orbital. Thus, models with the softest symmetry energy are the first ones to drip neutrons. Further, in anticipation of the upcoming 1% measurement of the neutron radius of ${}^{208}\mathrm{Pb}$ at the Thomas Jefferson Laboratory, a close relationship between the neutron radius of ${}^{208}\mathrm{Pb}$ and neutron radii of elements of relevance to atomic parity-violating experiments is established.

The relativistic Hartree approach describing the bound states of both nucleons and antinucleons in finite nuclei has been extended to include tensor couplings for the $\omega$ and $\rho$ mesons. After readjusting the parameters of the model to the properties of spherical nuclei, the effect of tensor-coupling terms raises the spin-orbit force by a factor of 2, while a large effective nucleon mass $m^{*}{/M}_N\approx 0.8$ sustains. The overall nucleon spectra of shell-model states are improved evidently. The predicted antinucleon spectra in the vacuum are deepened about 20–30 MeV.

New experimental data for the inclusive reactions $\mathrm{}(p,xp)\mathrm{}$ and $\mathrm{}(p,xd)\mathrm{}$ on isotopes of the nuclei ${}^{90,92}\mathrm{Zr}$ and ${}^{92}\mathrm{Mo},$ have been measured at $E_p=30.3\mathrm{}\mathrm{MeV},$ which has not been investigated in detail so far. We show the extension of the preequilibrium reactions to this energy region and interpret the results of these experiments. Moreover, we display the mechanism of the reaction and the level of energy dependence. The adequacy of the theoretical models in explaining the measured experimental data is also discussed. In our theoretical analysis, the contributions of multistep direct and compound processes in the formation of cross sections are determined and we assert that the traditional frameworks are valid for the description of the experimental data.

Experimental measurements of cross sections for knockout of one neutron from even-even and odd-odd projectiles with equal proton and neutron numbers at energies of about 600 MeV/nucleon on a hydrogen target show that the cross section for odd-odd projectiles is about three times smaller than for even-even projectiles and Monte Carlo calculations are used to explain this difference.

We suggest a multifragmentation scenario in which fragments are produced at an early, high temperature and high density, stage of the reaction. In this scenario, self-bound clusters of particles in the hot and dense fluid are the precursors of the observed fragments. This solves a number of recurrent problems concerning the kinetic energies and the temperature of the fragments, encountered with the standard low density fragmentation picture. The possibility to recover the initial thermodynamic parameters $(T$ and $\rho )$ from the inspection of the asymptotic fragment size and kinetic energy distributions is discussed.

Properties of evaporation residues and the accompanying light particles have been measured in ${}^{60}\mathrm{Ni}{+}^{92,100}\mathrm{Mo}$ fusion reactions at bombarding energies from $E/A=5\mathrm{}$ to 9 MeV. The data indicate that these reactions are essentially complete-fusion reactions with only a small amount of nonequilibrium emission at the highest bombarding energy studied. The measured kinetic-energy spectra of evaporated n, p, d, t, ${}^3\mathrm{He},$ and $\alpha$ particles are compared to statistical-model predictions. It is found that a constant excitation-energy independent level-density parameter is not able to reproduce these spectra over the compound-nucleus excitation-energy range from 90 to 250 MeV. The kinetic-energy spectra for all particles were fit using the level-density parametrization $a=A/(7+1.3\mathrm{}\times U/A){\mathrm{MeV}}^{-1},$ where U is the thermal excitation energy. The Coulomb barriers for charged-particle emission were reduced from the standard values to reproduce the peak energy and multiplicity for $\alpha$ particles. Using these ingredients, the measured mass, velocity, and angular distributions of evaporation residues are also reproduced. The average Z and N of the evaporation residues deduced from the light-particle multiplicities are in agreement with the predicted location of the evaporation attractor line. A neutron-proton asymmetry dependence of the level-density parameter is shown to have potentially important consequences for the neutron or proton richness of the evaporation residues. However, no evidence for such an effect is found in the measured data; and from the experimental multiplicity ratio of ${t/}^3\mathrm{He}$ it was deduced that any such dependence in the excitation-energy regime $100<\mathrm{}{E}^{*}<250\mathrm{}\mathrm{MeV}$ is very small.

The φ meson spectrum, which in vacuum is dominated by its coupling to the $\overline{K}K$ system, is modified in nuclear matter. Following a model based on chiral SU(3) dynamics we calculate the φ meson self-energy in nuclear matter considering the K and $\overline{K}$ in-medium properties. For the latter we use the results of previous calculations which account for S- and P-wave kaon-nucleon interactions based on the lowest order meson-baryon chiral effective Lagrangian, and this leads to a dressing of the kaon propagators in the medium. In addition, a set of vertex corrections is evaluated to fulfill gauge invariance, which involves contact couplings of the φ meson to S-wave and P-wave kaon-baryon vertices. Within this scheme the mass shift and decay width of the φ meson in nuclear matter are studied.

The purpose of this Rapid Communication is to show that recent data on the ground-state band and excited states based on the $0_2^{+}$ level in ${}^{150}\mathrm{Nd}$ and ${}^{152}\mathrm{Sm},$ especially the measured $B\left(E2\mathrm{}\right)\mathrm{}$ values, can be well described by including a $\Delta K=0\mathrm{}$ coupling between rotational bands. This is contrary to recent statements in the literature. The experimental data are compared with models that have supported the widely differing interpretations of these transitional nuclei. These interpretations include describing excited states as rotational excitations of single-phonon states, the multiphonon “phase coexistence” picture, and the $X\left(5\right)\mathrm{}$ critical-point description.

The transition quadrupole moments $Q_t$ for the superdeformed band in ${}^{40}\mathrm{Ca}$ have been determined through thin-target Doppler-shift attenuation analyses. A best-fit value of $Q_t=1.30\mathrm{}\pm 0.05$ $e\mathrm{b}$ is obtained when a single value is assumed for the entire band. Fitting separate quadrupole moments for in-band transitions decaying from the high-spin states and the presumably admixed low-spin states results in $Q_t(\mathrm{high}{)=1.81\mathrm{}}_{-0.26}^{+0.41\mathrm{}}$ $e\mathrm{b}$ and $Q_t(\mathrm{low}{)=1.18\mathrm{}}_{-0.05}^{+0.06\mathrm{}}$ $e\mathrm{b},$ respectively. $Q_t$ values extracted for individual transitions in a Doppler-broadened line-shape analysis also indicate smaller $Q_t$ values at lower spins. These results are consistent with the interpretation of this band as an eight-particle–eight-hole superdeformed band with a significant admixture of less-collective configurations at low spins.

The half-life of ${}^{45}\mathrm{Fe}$ calculated using an R-matrix formula for the contribution due to di-proton decay agrees with experimental values, provided the available decay energy is near the upper limit of the experimental range.