Spurred by the recent complete determination of the weak currents in two-nucleon systems up to $\mathcal{O}{(Q}^3)$ in heavy-baryon chiral perturbation theory, we carry out a parameter-free calculation of the threshold S factors for the solar $\mathrm{pp}$ (proton-fusion) and hep processes in an effective field theory (EFT) that combines the merits of the standard nuclear physics method and systematic chiral expansion. The power of the EFT adopted here is that one can correlate in a unified formalism the weak-current matrix elements of two-, three-, and four-nucleon systems. Using the tritium $\beta$-decay rate as an input to fix the only unknown parameter in the theory, we can evaluate the threshold S factors with drastically improved precision; the results are $S_{\mathrm{pp}}\mathrm{}\left(0\right)=3.94\mathrm{}\times (1\mathrm{}\pm 0.004)\times {10}^{-25}\mathrm{MeV}\mathrm{}\mathrm{b}$ and $S_{\mathrm{hep}}\mathrm{}\left(0\right)=(8.6\mathrm{}\pm 1.3)\times {10}^{-20}\mathrm{keV}\mathrm{}\mathrm{b}.$ The dependence of the calculated S factors on the momentum cutoff parameter $\Lambda$ has been examined for a physically reasonable range of $\Lambda .$ This dependence is found to be extremely small for the $\mathrm{pp}$ process, and to be within acceptable levels for the hep process, substantiating the consistency of our calculational scheme.

This paper deals with the theoretical foundation of effective two-body forces for the generator coordinate method and the projected mean-field method. The first aim of this paper is to reduce the in-medium content of a generalized G matrix, removing the hard-core problem in this extended context, into various local densities. Then, we consider the possible renormalization of multibody forces through a density-dependent two-body interaction in the context of configuration mixing calculations. A density dependence of the form ${\rho }^{\sigma },$ as used in Skyrme and Gogny forces, is successfully interpreted as doing so when the mixed density is used. Finally, we propose a simple extension of the Skyrme force dedicated to the calculation of matrix elements between nonorthogonal product states, which are needed to evaluate the correlated energy.

The knowledge of the nuclear spin- and parity-dependent level densities $\rho (E,J,\pi )$ is important for understanding statistical properties of nuclei and reaction rates. We show that the earlier suggested method of exponential extrapolation, which allows one to find the yrast energy with high accuracy even for very large shell model Hamiltonian matrices, can be combined with the formalism of statistical spectroscopy in order to obtain the reliable level density.

Large-scale shell model calculations were performed in the full $Z=82\mathrm{}–126$ proton model space $\pi {(0h}_{9/2},$ ${1f}_{7/2},$ ${0i}_{13/2},$ ${2p}_{3/2},$ ${1f}_{5/2},$ ${2p}_{1/2})$ employing the code NATHAN. The modified Kuo-Herling interaction was used, no truncation was applied up to protactinium $\mathrm{}(Z=91\mathrm{})\mathrm{}$ and seniority truncation beyond. The results are compared to experimental data including binding energies, level schemes, and electromagnetic transition rates. An overall excellent agreement is obtained for states that can be described in this model space. Limitations of the approach with respect to excitations across the $Z=82\mathrm{}$ and $N=126\mathrm{}$ shells and deficiencies of the interaction are discussed.

We discuss the accuracy of mass models for extrapolating to very asymmetric nuclei and the impact of such extrapolations on the predictions of isotopic observables in multifragmentation. We obtain improved mass predictions by incorporating measured masses and extrapolating to unmeasured masses with a mass formula that includes surface symmetry and Coulomb terms. We find that using accurate masses has a significant impact on the predicted isotopic observables.

In the present paper we investigate incoherent ${\rho }^0$ electroproduction off complex nuclei. We derive a novel, simple expression for the incoherent electroproduction cross section in which one can clearly separate the final state interactions of the reaction products from the “initial state interactions” of the photon that give rise to nuclear shadowing. In the special case of purely absorptive final state interactions, we deduce from our expression the known Glauber result. A more realistic treatment of the final state interactions within a transport model is then used to compare our predictions with experimental data from the HERMES experiment.

We report the results of a new measurement of spin structure functions of the deuteron in the region of moderate momentum transfer $[Q^2=0.27\mathrm{}–1.3(\mathrm{GeV}{/c)}^2]$ and final hadronic state mass in the nucleon resonance region $(W=1.08\mathrm{}–2.0\mathrm{GeV}).\mathrm{}$ We scattered a 2.5 GeV polarized continuous electron beam at Jefferson Lab off a dynamically polarized cryogenic solid state target ${(}^{15}{\mathrm{ND}}_3)$ and detected the scattered electrons with the CEBAF large acceptance spectrometer. From our data, we extract the longitudinal double spin asymmetry $A_{||}$ and the spin structure function $g_1^d.$ Our data are generally in reasonable agreement with existing data from SLAC where they overlap, and they represent a substantial improvement in statistical precision. We compare our results with expectations for resonance asymmetries and extrapolated deep inelastic scaling results. Finally, we evaluate the first moment of the structure function $g_1^d$ and study its approach to both the deep inelastic limit at large $Q^2$ and to the Gerasimov-Drell-Hearn sum rule at the real photon limit ${(Q}^2\to 0).$ We find that the first moment varies rapidly in the $Q^2$ range of our experiment and crosses zero at $Q^2$ between 0.5 and $0.8(\mathrm{GeV}{/c)}^2,$ indicating the importance of the $\Delta$ resonance at these momentum transfers.

We report measurements of cross sections for the reaction ${}^1\mathrm{H}{(e,e}^{\prime }{K}^{+})Y,$ for both the Λ and ${\Sigma }^0$ hyperon states, at an invariant mass of $W=1.84\mathrm{}\mathrm{GeV}$ and four-momentum transfers $0.5<\mathrm{}{Q}^2<2\mathrm{}(\mathrm{GeV}{/c)}^2.$ Data were taken for three values of virtual photon polarization $\epsilon ,$ allowing the decomposition of the cross sections into longitudinal and transverse components. The Λ data are a revised analysis of prior work, whereas the ${\Sigma }^0$ results have not been previously reported.

Recent compilations of experimental gross $\beta$-decay properties, i.e., half-lives ${(T}_{1/2})$ and neutron-emission probabilities ${(P}_{\mathrm{n}}),$ are compared to improved global macroscopic-microscopic model predictions. The model combines calculations within the quasiparticle (QP) random-phase approximation for the Gamow-Teller (GT) part with an empirical spreading of the QP strength and the gross theory for the first-forbidden part of ${\beta }^{-}$ decay. Nuclear masses are either taken from the 1995 data compilation of Audi et al., when available, otherwise from the finite-range droplet model. Especially for spherical and neutron-(sub-)magic isotopes a considerable improvement compared to our earlier predictions for pure GT decay (ADNDT, 1997) is observed. $T_{1/2}$ and $P_{\mathrm{n}}$ values up to the neutron drip line have been used in r-process calculations within the classical “waiting-point” approximation. With the new nuclear-physics input, a considerable speeding-up of the r-matter flow is observed, in particular at those r-abundance peaks which are related to magic neutron-shell closures.

A four-body calculation of the $\mathrm{pn}\Lambda \Lambda$ bound state, ${}_{\Lambda \Lambda }^4\mathrm{H},$ is performed using the stochastic variational method and phenomenological potentials. The $NN,$ $\Lambda N,$ and $\Lambda \Lambda$ potentials are taken from a recent paper by Filikhin and Gal [Phys. Rev. Lett. 89, 172502 (2002)]. Although their Faddeev-Yakubovsky calculation found no bound-state solution over a wide range of $\Lambda \Lambda$ interaction strengths, the present variational calculation gives a bound-state energy that is clearly lower than the ${}_{\Lambda }^3\mathrm{H}+\Lambda$ threshold, even for a weak $\Lambda \Lambda$ interaction strength deduced from a recent experimental $B_{\Lambda \Lambda }$${(}_{\Lambda \Lambda }^6\mathrm{He})$ value. The binding energies obtained are close to, and slightly larger than, the values obtained from the three-body $d\Lambda \Lambda$ model in the paper.

Results for response functions for kaon electroproduction on the proton are presented. A tree-level hadrodynamical model is adopted and it is shown that some of the electroproduction response functions are particularly powerful with the eye on gaining control over the parametrization of the background diagrams. The existing dataset for the ${p(e,e}^{\prime }{K}^{+})\Lambda$ reaction appears to rule out the use of a $g_{K^{+}\Lambda p}$ coupling constant beyond the boundaries of softly broken SU(3) flavor symmetry. Also the use of soft hadronic form factors, which has been proposed as a valid alternative for a hadrodynamical description of the $p\left(\gamma {,K}^{+}\right)\Lambda$ data in the resonance region, seems to be disfavored by the magnitude of the measured ${p(e,e}^{\prime }{K}^{+})\Lambda$ cross sections.

Thomas-Fermi theory is developed to evaluate nuclear matrix elements averaged on the energy shell, on the basis of independent particle Hamiltonians. One- and two-body matrix elements are compared with the quantal results, and it is demonstrated that the semiclassical matrix elements, as function of energy, well pass through the average of the scattered quantum values. For the one-body matrix elements it is shown how the Thomas-Fermi approach can be projected on good parity and also on good angular momentum. For the two-body case, the pairing matrix elements are considered explicitly.

A new method for extracting neutron densities from intermediate-energy elastic proton-nucleus scattering observables uses a global Dirac phenomenological approach based on the relativistic impulse approximation. Datasets for ${}^{40}\mathrm{Ca},$ ${}^{48}\mathrm{Ca},$ and ${}^{208}\mathrm{Pb}$ in the energy range from 500 MeV to 1040 MeV are considered. The global fits are successful in reproducing the data and in predicting datasets not included in the analysis. Using this global approach, energy-independent neutron densities are obtained. The vector point proton density distribution ${\rho }_v^p$ is determined from the empirical charge density after unfolding the proton form factor. The other densities, ${\rho }_v^n,$ ${\rho }_s^p,$ ${\rho }_s^n,$ are parametrized. This work provides energy-independent values for the rms neutron radius $R_n$ and the neutron skin thickness $S_n,$ in contrast to the energy-dependent values obtained by previous studies. In addition, the results presented in this paper show that the expected rms neutron radius and the skin thickness for ${}^{40}\mathrm{Ca}$ are accurately reproduced. The values of $R_n$ and $S_n$ obtained from the global fits that we consider to be the most reliable are given as follows: for ${}^{40}\mathrm{Ca},$ $3.314>\mathrm{}{R}_n>3.310\mathrm{}\mathrm{fm}$ and $-0.063>\mathrm{}{S}_n$ $>-0.067\mathrm{fm};$ for ${}^{48}\mathrm{Ca},$ $3.459>\mathrm{}{R}_n>3.413\mathrm{}\mathrm{fm}$ and $0.102>\mathrm{}{S}_n>0.056\mathrm{}\mathrm{fm};$ and for ${}^{208}\mathrm{Pb},$ $5.550>\mathrm{}{R}_n>5.522\mathrm{}\mathrm{fm}$ and $0.111>\mathrm{}{S}_n>0.083\mathrm{}\mathrm{fm}.$ These values are in reasonable agreement with nonrelativistic Skyrme-Hartree-Fock models and with relativistic Hartree-Bogoliubov models with density-dependent meson-nucleon couplings. The results from the global fits for ${}^{48}\mathrm{Ca}$ and ${}^{208}\mathrm{Pb}$ are generally not in agreement with the usual relativistic mean-field models.

We show that the cross section for direct $E0\mathrm{}$ pair emission is related to the cross section for direct $E2\mathrm{}$ photon emission, and is a negligible contribution to the total capture cross section for ${}^3\mathrm{He}{+}^4{\overrightarrow{\mathrm{He}}}^7\mathrm{Be}.$ $E0\mathrm{}$ resonance emission, $E1\mathrm{}$ pair emission, and internal conversion are also negligible. Thus there cannot be significant contributions to the ${}^3\mathrm{He}{+}^4{\overrightarrow{\mathrm{He}}}^7\mathrm{Be}$ capture cross section at low energies from electromagnetic emission processes other than single photon emission.

A method is proposed for the experimental measurement of neutron separation energies for nuclei far from stability. The procedure is based on determining cross sections for the production of nuclei, by projectile fragmentation, for which only protons are removed but for which the number of neutrons is left unchanged. A simple abrasion-ablation analysis leads to a cross section prediction that is sensitive to the neutron separation energy after a single parameter is adjusted in comparison with data. Examples that illustrate the method are presented.

An excited rotational band including seven new $\gamma$ transitions was identified in ${}^{97}\mathrm{Sr}$ from $\gamma -\gamma -\gamma$ coincidences in the spontaneous fission of ${}^{252}\mathrm{Cf}.$ This new band, built on the 829.8-keV state, is interpreted as the $\nu 9/2\left[404\right]$ rotational band with a very deformed shape. The half-life of the 829.8-keV state is determined to be 265(27) ns in the present work. The new band indicates that the emptying of the upsloping $g_{9/2}$ orbital with $K=9/2\mathrm{}$ is closely related to the strong prolate shapes of some bands in the Sr and Zr regions with $A\approx 100.$

We investigate the role of the Coulomb and the vector-isovector ρ potentials in the asymmetry of the neutron and proton pseudospin splittings in nuclei. To this end, we solve the Dirac equation for the nucleons using central vector and scalar potentials with Woods-Saxon shape, and Z and $N-Z$ dependent Coulomb and $\rho$ potentials added to the vector potential. We study the effect of these potentials on the energy splittings of proton and neutron pseudospin partners along a Sn isotopic chain. We use an energy decomposition proposed in a previous work to assess the effect of a pseudospin-orbit potential on those splittings. We conclude that the effect of the Coulomb potential is quite small, and the $\rho$ potential gives the main contribution to the observed isospin asymmetry of the pseudospin splittings. This isospin asymmetry results from a cancellation of the various energy terms and cannot be attributed only to the pseudospin-orbit term, confirming the dynamical character of this symmetry pointed out in previous works.

The mean lifetimes of seven states in ${}^{113}\mathrm{I}$ excited via the reaction ${}^{58}\mathrm{Ni}{(}^{58}\mathrm{Ni},3p)$ at a beam energy of 210 MeV were measured for the first time by means of the recoil-distance Doppler-shift technique. The lifetimes were determined in coincidence mode within the framework of the differential decay-curve method. The quadrupole deformation derived from the $B\left(E2\mathrm{}\right)\mathrm{}$ values at the bottom of the negative-parity yrast band confirms the predictions of previous TRS calculations. At higher excitation energy along the yrast line, the experimental $B\left(E2\mathrm{}\right)\mathrm{}$ transition strengths indicate an apparent loss of collectivity with increasing spin. A three-band mixing calculation provides an overall description of these strengths.

We present simple analytic expressions that parametrize the soft photon production rates likely to be produced in relativistic heavy ion collisions due to bremsstrahlung processes for quark matter and hadronic matter.

Quadrupole amplitudes in the ${\gamma }^{*}\overrightarrow{N}\Delta$ transition are associated with the issue of nucleon deformation. A search for these small amplitudes has been the focus of a series of measurements undertaken at Bates/MIT by the OOPS Collaboration. We report on results from $\mathrm{H}{(e,e}^{\prime }p){\pi }^0$ data obtained at $Q^2=0.070\mathrm{}(\mathrm{G}\mathrm{e}\mathrm{V}/{c)}^2$ and invariant mass of $W=1155\mathrm{}\mathrm{MeV}$ using the out-of-plane detection technique with the OOPS spectrometers. The ${\sigma }_{\mathrm{LT}}$ and ${\sigma }_T+\epsilon {\sigma }_L$ response functions were isolated. These results, along with those of previous measurements at $W=1172\mathrm{}\mathrm{MeV}$ and $Q^2=0.127\mathrm{}(\mathrm{G}\mathrm{e}\mathrm{V}/{c)}^2,$ aim in elucidating the interplay between resonant and nonresonant amplitudes.