Based on symmetry consideration, more generalized chiral field terms are proposed to restore the chiral SU(2${)}_{\mathit{L}}$×SU(2${)}_{\mathit{R}}$ symmetry of strong interaction. As a result, a modified quark-quark interaction is obtained. Applying this interaction to nucleon-nucleon scattering, the agreement between the theoretical phase shifts of partial waves and experimental data is improved.

Relativistic exchange current corrections to the impulse approximation in low and intermediate energy neutrino-nucleus scattering are presented assuming nonvanishing strange quark form factors for constituent nucleons. Two-body exchange current operators which treat all SU(3) vector and axial currents on an equal footing are constructed by generalizing the soft-pion dominance method of Chemtob and Rho. For charged current reactions, exchange current corrections can reduce the impulse approximation results by 5 to 10 % depending on the nuclear density. A finite strange quark form factor may change the total cross section for neutral current scattering by 20% while exchange current corrections are found to be sensitive to the nuclear density. Implications on the current LSND experiment to extract the strange quark axial form factor of the nucleon are discussed.

We calculate the shape of the ${\mathrm{\beta }}^{\mathrm{-}}$ and ${\mathrm{\beta }}^{+}$ spectra in the A=14 system using constraints from measurements of the width of the M1 transition, ${}_{}{}^{14}{}_{}{}^{}\mathrm{N}$(e,${\mathit{e}}^{\prime }$) cross section, and logft values, as well as shell-model wave functions. Our result for the shape factor assuming conservation of vector current disagrees by a factor of 2 with existing data from ${}_{}{}^{14}{}_{}{}^{}\mathrm{O}$ ${\mathrm{\beta }}^{+}$ decay.

The role of the off-shell dependence of ρ-ω mixing in the charge symmetry breaking nucleon-nucleon potential is discussed. It is shown that models describing the off-shell dependence of ρ-ω mixing are not sufficient to determine the charge symmetry breaking nucleon-nucleon potential.

Motivated by a recent experiment at LAMPF we calculate cross sections for muon-neutrino and muon-antineutrino charged-current reactions on ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ within the continuum RPA model. We also determine the branching ratios for the main decay channels of these reactions by application of a statistical model.

At the Karlsruhe pulsed 3.75 MV Van de Graaff accelerator the ${}_{}{}^{36}{}_{}{}^{}\mathrm{S}$(n,γ${)}^{37}$S(5.05 min) cross section was measured by the fast cyclic activation technique via the 3.103 MeV γ-ray line of the ${}_{}{}^{37}{}_{}{}^{}\mathrm{S}$ decay. Samples of elemental sulfur enriched in ${}_{}{}^{36}{}_{}{}^{}\mathrm{S}$ by 5.933% were irradiated between two gold foils which served as capture standards. The capture cross section was measured at neutron energies 25, 151, 176, and 218 keV, respectively. The ${}_{}{}^{36}{}_{}{}^{}\mathrm{S}$(n,γ${)}^{37}$S cross section in the thermonuclear and thermal energy range has been calculated using the direct-capture (DC) model combined with the folding procedure used for the determination of the potentials. The nonresonant experimental data for this reaction can be reproduced excellently using this method. The input parameters of the DC calculation (masses, Q values, nuclear density distributions, spectroscopic factors, spin-parity assignments, and excitation energies of the low-lying states of the residual nucleus) have been taken from the available experimental data.

The production of fast neutrons and pions by inelastic interactions of cosmic-ray muons in an organic liquid scintillator has been investigated. A detector filled with 190 liters of a 0.09% gadolinium-loaded liquid scintillator was installed in the Stanford Underground Facility, at an underground depth of approximately 20 meters water equivalent. The detector served as the target material for hadron production. Our measurements find a single-neutron production yield of (4.3±0.3±0.8)×${10}^{\mathrm{-}5}$ neutrons per muon g/${\mathrm{cm}}^2$ and a double-neutron production yield of (1.6±0.2±0.5)×${10}^{\mathrm{-}5}$ double neutrons per muon g/${\mathrm{cm}}^2$. We measured a ${\mathrm{\pi }}^{+}$ production yield of (3.5±0.2±0.7)×${10}^{\mathrm{-}6}$ pions per muon g/${\mathrm{cm}}^2$. Nearly all the ${\mathrm{\pi }}^{+}$ produced were accompanied by neutrons. These yields were dependent on the energy threshold of the muon trigger, revealing an enhancement associated with hadronic showers initiated by muons. The production yield due to nonshowering muons was lower: 2×${10}^{\mathrm{-}5}$ neutrons per muon g/${\mathrm{cm}}^2$, with a single-to-double neutron multiplicity ratio of roughly 4:1. The nonshowering muon ${\mathrm{\pi }}^{+}$ production probability was 2.5×${10}^{\mathrm{-}6}$ pions per muon g/${\mathrm{cm}}^2$, with about half of these nonshowering ${\mathrm{\pi }}^{+}$ events accompanied by neutrons.

Electron capture and β decay of nuclei in the core of massive stars play an important role in the stages leading to a type II supernova explosion. Nuclei in the f-p shell are particularly important for these reactions in the post-silicon-burning stage of a presupernova star. In this paper we characterize the energy distribution of the Gamow-Teller giant resonance (GTGR) for mid-fp-shell nuclei in terms of a few shape parameters, using data obtained from high energy, forward scattering (p,n) and (n,p) reactions. The energy of the GTGR centroid ${\mathit{E}}_{\mathrm{GT}}$ is further generalized as a function of nuclear properties such as mass number, isospin, and other shell model properties of the nucleus. Since a large fraction of the GT strength lies in the GTGR region, and the GTGR is accessible for weak transitions taking place at energies relevant to the cores of presupernova and collapsing stars, our results are relevant to the study of important ${\mathit{e}}^{\mathrm{-}}$ capture and β-decay rates of arbitrary, neutron-rich, f-p shell nuclei in stellar cores. Using the observed GTGR and isobaric analog states (IAS) energy systematics we compare the coupling coefficients in the Bohr-Mottelson two particle interaction Hamiltonian for different regions of the isotope table.

We examine the presence of strangeness-bearing components, hyperons and kaons, in dense neutron star matter. Calculations are performed using relativistic mean field models, in which both the baryon-baryon and kaon-baryon interactions are mediated by meson exchange. Results of kaon condensation are found to be qualitatively similar to previous work with chiral models, if compatibility of the kaon optical potentials is required. The presence of strangeness, be it in the form of hyperons or kaons, implies a reduction in the maximum mass and a relatively large number of protons, sufficient to allow rapid cooling to take place. The need to improve upon the poorly known couplings of the strange particles, which determine the composition and structure of neutron stars, is stressed. We also discuss generic problems with effective masses in mean field theories.

We consider the radiative capture process α+d${\to }^6$Li+γ at energies, ${\mathit{E}}_{\mathrm{c}.\mathrm{m}.\mathrm{}}$≤300 keV, that are relevant for astrophysical processes. Due to the peripheral character of the reaction, the overall normalization of the astrophysical factor ${\mathit{S}}_{24}$ is entirely governed by one quantity, the asymptotic normalization coefficient ${\mathit{C}}_{01}$ for ${}_{}{}^6{}_{}{}^{}\mathrm{\alpha }$+d. Using the recently well established value for this constant ${\mathit{C}}_{01}$=2.3±0.12 ${\mathrm{fm}}^{\mathrm{-}1/2}$, we calculated ${\mathit{S}}_{24}$ taking into account both E1 and E2 contributions. Our recommended value for ${\mathit{S}}_{24}$ is 2.57 MeV nb at the most effective energy for the capture reaction in astrophysical processes, ${\mathit{E}}_{\mathrm{c}.\mathrm{m}.\mathrm{}}$=70 keV, which gives a reaction rate 0.036 ${\mathrm{cm}}^3$ ${\mathrm{mole}}^{\mathrm{-}1}$ ${\mathrm{s}}^{\mathrm{-}1}$ at the temperature 0.8×${10}^9$ K. We found a significant energy dependence of ${\mathit{S}}_{24}$ at astrophysical energies. At energies of less than 110 keV, the E1 component dominates over the E2 component. At ${\mathit{E}}_{\mathrm{c}.\mathrm{m}.\mathrm{}}$=70 keV, the E1 contribution to the total transition is about 58%.

Previous work has examined light particle correlations from O+Al reactions over a range of energies within a framework of statistical emission from a composite source. The source of these light particles was assumed to be an excited composite nucleus because the excitation energy of the source was not so high that exotic processes such as fragmentation or preequilibrium emission were significant. In this Brief Report we examine correlation functions between light charged particles emitted from reactions of S+Al at 105 MeV and 215 MeV. As in previous work, the proton-proton and proton-deuteron correlations are well described by the results of Monte Carlo simulations based on statistical emission. In this Brief Report we will also compare the results of alpha-alpha and deuteron-alpha correlations to the predictions of models which include the emission of heavier unstable particles (such as ${}_{}{}^8{}_{}{}^{}\mathrm{Be}$ and ${}_{}{}^6{}_{}{}^{}\mathrm{Li}_{}^{\mathrm{*}}{}_{}{}^{}$) from the excited source. The results presented here can serve as additional validation of the correlation technique and also as tests of the statistical model.

In order to identify double-γ vibrational states in well-deformed regions, we have made a Coulomb excitation experiment for ${}_{}{}^{168}{}_{}{}^{}\mathrm{Er}$. We could observe 1235-keV and 962-keV γ transitions decaying from the 2056-keV $4^{+}$ state. The measured E2 transition probabilities support the assignment of the $4^{+}$ state as a two-phonon γ-vibrational state.

Until now the only way to study the strangeness changing baryon-baryon interaction has been through the decays of lambda hypernuclei. It would clearly be preferable to be able to study reactions such as pn→pΛ in free space. In order to provide some guidance concerning the feasibility of such a measurement, we investigate the energy dependence, parity violating asymmetry, and shape of the cross section for this reaction.

Pion-photoproduction data is examined to check for the nucleon-helicity conservation predicted by asymptotic QCD. The differential cross section shows agreement with constituent-counting rules, and polarization data are not in disagreement with conservation of nucleon helicity. However large uncertainties in the polarization measurements do not allow a conclusive statement. The helicity amplitudes from a partial-wave analysis are also examined for helicity conservation. While the amplitudes become small as s increases, the s dependence of the helicity-conserving amplitudes is similar to the dependence of the nonconserving amplitudes.

We consider pion exchange between nucleons in the one-boson-exchange model and in a model based upon the use of the quark-quark $T$ matrices of the Nambu-Jona-Lasinio (NJL) model. We study the relation between the meson-nucleon form factors of the boson-exchange model and the form factors that appear in our application of the NJL model. Previously we indicated that the form factors of the boson-exchange model are not physical quantities. For example, we saw that, while the vertex form factor of the boson-exchange model depends upon a parameter ${\Lambda }_{\pi }=1.3\mathrm{}$ GeV in the case of pion exchange, the corresponding physical parameter characterizing the meson-nucleon vertex is ${\Lambda }_{\pi }\simeq 0.8$ GeV. In this paper we study how the mixing of the pion and the axial-vector ($T=1\mathrm{}$) mode affects the value of ${\lambda }_{\pi }$ needed in our model. We find that the two models of pion exchange in the nucleon-nucleon interaction can be put into excellent agreement if ${\lambda }_{\pi }=0.9\mathrm{}$ GeV is used.

The proton drip-line nucleus ${}_{}{}^{17}{}_{}{}^{}\mathrm{Ne}$ is studied in a three-body model of ${}_{}{}^{15}{}_{}{}^{}\mathrm{O}$ plus two protons. The ${}_{}{}^{17}{}_{}{}^{}\mathrm{Ne}$ nucleus has a Borromean binding structure, and calculations show a rms matter radius of 2.77–2.81 fm, in agreement with experiment. The model gives a proton radius excess about 0.26–0.32 fm over the neutron radius, showing that a proton skin is present. The 73% probability of a valence proton being outside the rms core radius is sufficiently large, however, to indicate a halo. Predictions for the momentum distributions of ${}_{}{}^{15}{}_{}{}^{}\mathrm{O}$ fragments are given, and these, if verified, would also suggest a two-proton halo structure for ${}_{}{}^{17}{}_{}{}^{}\mathrm{Ne}$. This would be the first identification of a two-proton halo nucleus.

The ${\mathit{E}}_{\mathrm{\alpha },\mathrm{l}\mathrm{a}\mathrm{b}}$=679 keV (5/$2^{+}$) and ${\mathit{E}}_{\mathrm{\alpha },\mathrm{l}\mathrm{a}\mathrm{b}}$=687 keV (3/$2^{\mathrm{-}}$) resonances in the ${}_{}{}^{15}{}_{}{}^{}\mathrm{N}$(α,γ${)}^{19}$F reaction have been analyzed using a windowless gas target system and a 100% relative efficiency germanium detector with an active BGO shielding. The strength of the ${\mathit{E}}_{\mathrm{\alpha },\mathrm{l}\mathrm{a}\mathrm{b}}$=687 keV resonance has been determined: ωγ= 8±3 μeV. The strength of the ${\mathit{E}}_{\mathrm{\alpha },\mathrm{l}\mathrm{a}\mathrm{b}}$=461 keV resonance and the properties of the corresponding resonances in the mirror reaction ${}_{}{}^{15}{}_{}{}^{}\mathrm{O}$(α,γ${)}^{19}$Ne have been derived using a realistic folding potential.

Yields and angular distributions of the transfer reaction products have been measured in the ${}_{}{}^{19}{}_{}{}^{}\mathrm{F}$${+}^{232}$Th reaction at bombarding energies near the Coulomb barrier. The transfer probabilities were calculated (${\mathit{P}}_{\mathrm{tr}}$) from the measured differential cross sections at the grazing angle, for the most dominant channels for given (ΔN) transfers. The values of ${\mathit{P}}_{\mathrm{tr}}$ show, in general, an exponential dependence on the ground state Q value (${\mathit{Q}}_0$) of the reaction and the large cross sections observed for 1α and 2α transfer channels are largely accounted by the Q-value variations. However, the transfer channels of ΔN=5, 9, and 12 leading to ${}_{}{}^{14}{}_{}{}^{}\mathrm{C}$, ${}_{}{}^{10}{}_{}{}^{}\mathrm{Be}$, and ${}_{}{}^7{}_{}{}^{}\mathrm{Li}$ products, respectively, show strong enhancements in the transfer probabilities. The large cross sections in these channels may imply simultaneous correlated transfers of (αp), (αp,α), and (3α) clusters from the ${}_{}{}^{19}{}_{}{}^{}\mathrm{F}$ projectile to the target.