We suggest an effective quark model for low-lying baryon octet and decuplet motivated by QCD with a linearly rising confinement potential incorporating the extended Nambu–Jona-Lasinio (ENJL) model with linear realization of chiral $U\left(3\right)\mathrm{}\times U\left(3\right)\mathrm{}$ symmetry. Baryons are considered as external heavy states coupled to local three-quark currents with fixed spinorial structure and to low-lying mesons through quark-meson interactions defined in the ENJL model. In the constituent quark loop representation we have calculated the coupling constants of the $\pi NN,\hspace{0.5em}\pi N\Delta ,$ and $\gamma N\Delta$ interactions and the ${\sigma }_{\pi N}$ term. The obtained results are in reasonable agreement with experimental data and other effective field theory approaches.

We used the $N\Delta$ and $\Delta \Delta$ potentials derived from the chiral quark cluster model to analyze the bound-state problem of the $N\Delta$ and $N\Delta \Delta$ systems when the two-body subsystems can be in S-wave states. We found that the $N\Delta$ system has only one bound state right at the $N\Delta$ threshold while for the $N\Delta \Delta$ system there are no bound-state solutions in any of the allowed channels, although a couple of them are nearly bound. Our model predicts the $\mathrm{NN}$ ${}^1{D}_2$ resonance as being a bound state of the $N\Delta$ system at the $N\Delta$ threshold.

Starting from a unitary effective Lagrangian model for the meson-nucleon scattering developed in T. Feuster and U. Mosel, Phys. Rev. 58, 457 (1998), we come to a unified description of both meson scattering and photon-induced reactions on the nucleon. To this end the photon is added perturbatively, yielding both Compton scattering and meson photoproduction amplitudes. In a simultaneous fit to all available data the parameters of the nucleon resonances are extracted. We find that a global fit to the data of the various channels involving the final states $\gamma N,$ $\pi N,$ $\pi \pi N,$ $\eta N,$ and $K\Lambda$ is possible. Especially in eta photoproduction a readjustment of the masses and widths found in the fits to hadronic reactions alone is necessary to describe the data. Only for the $D_{13}\mathrm{}\left(1520\right)\mathrm{}$ do we find a possible disagreement for the helicity couplings extracted using the combined data set and pion photoproduction multipoles alone. The model dependence introduced by the restoration of gauge invariance is discussed and found to be significant mainly for resonances with small helicity couplings.

Because of its temperature-dependent half-life, ${}^{176}\mathrm{Lu}$ represents an important thermometer for the slow neutron capture process $(s$ process) which accounts for the origin of about half of the abundances between Fe and Bi. This interpretation of the observed ${}^{176}\mathrm{Lu}$ abundance has been improved by a new lifetime measurement of the $J^{\pi }{=5\mathrm{}}^{-}$ state at 838 keV in ${}^{176}\mathrm{Lu}.$ The present limit of ${\tau }_{838}>~10\hspace{0.5em}\mathrm{ps}$ provides a more stringent constraint for the thermal equilibration between the long-lived ground state ${(t}_{1/2}=41\mathrm{}\hspace{0.5em}\mathrm{Gyr})$ and the short-lived K isomer at 123 keV ${(t}_{1/2}=3.7\mathrm{}\hspace{0.5em}\mathrm{h}),$ and, hence, for the resulting estimate of the temperature during shell helium burning in red giant stars.

Gamow-Teller transition strengths obtained in the ${}^{127}\mathrm{I}{\mathrm{}(p,n)\mathrm{}}^{127}\mathrm{Xe}$ reaction studied at 94, 159, and 197 MeV incident proton energies are presented, and used to evaluate the efficiency of ${}^{127}\mathrm{I}$ as a solar neutrino detector. Excitation of the $J^{\pi }{=(3/2)\mathrm{}}^{+}$ first excited state at $E_x=0.125\mathrm{}\hspace{0.5em}\mathrm{MeV}$ in ${}^{127}\mathrm{Xe},$ sensitive to ${}^7\mathrm{Be}$ solar neutrinos, is evaluated. The sum of Gamow-Teller strength up to particle emission threshold and up to 20 MeV excitation energy are also reported. This paper also provides a new measurement of the Coulomb displacement energy $\Delta E_c,$ the excitation energy of the isobaric analog state, and the centroid of the Gamow-Teller resonance in ${}^{127}\mathrm{Xe}.$

Including nucleon-nucleon correlations due to both Fermi statistics and nuclear forces, we have developed a general formalism for calculating the charged-current neutrino-nucleon absorption rates in nuclear matter. We find that at one-half the nuclear density many-body effects alone suppress the rates by a factor of 2 and that the suppression factors increase to $\sim 5$ at $4\times {10}^{14}\hspace{0.5em}{\mathrm{g}\mathrm{}\mathrm{}\mathrm{}\mathrm{cm}}^{-3}.$ The associated increase in the neutrino-matter mean free paths parallels what we have found for neutral-current interactions and may open up interesting possibilities in the context of the delayed supernova mechanism and protoneutron star cooling.

The ratio of ${}^{18}\mathrm{O}$ nuclei to electrons in SuperKamiokande is quite small, about 1:5000. However, this nucleus provides two unpaired neutrons and a low threshold for solar neutrino absorption, resulting in an unusually large cross section. The ${}^{18}\mathrm{O}$ nuclei, together with ${}^{17}\mathrm{O}$ and deuterium, will produce in excess of 460 scattered electrons per year with energies above the initial SuperKamiokande threshold of 6.5 MeV, or about 6.7% of the total solar neutrino signal, for an electron neutrino flux scaled to the current SuperKamiokande counting rate. We explore whether this might complicate efforts to extract the neutrino spectrum from elastic scattering events and whether there might be any prospect of combining ${}^{18}\mathrm{O}$ and elastic scattering events to separate charged- and neutral-current interactions. Under current operating conditions the answers are no, as the Fermi, Gamow-Teller, and forbidden contributions to the ${}^{18}\mathrm{O}$ cross section conspire to produce a nearly isotropic cross section. Thus most of the events are indistinguishable from background. This result is relevant to SuperKamiokande detection of solar antineutrinos, which arise in certain oscillation scenarios.

The unreported heavy neutron-rich nuclide ${}^{238}\mathrm{Th}$ has been produced by $60\hspace{0.5em}\mathrm{M}\mathrm{e}\mathrm{V}/\mathrm{n}\mathrm{u}\mathrm{c}\mathrm{l}\mathrm{e}\mathrm{o}\mathrm{n}{}^{18}\mathrm{O}$ ion bombardment of natural uranium. Thorium was radiochemically separated from the uranium and reaction products. The growth and decay of ${}^{238}\mathrm{Pa}\gamma$ rays has been observed, identifying the ${}^{238}\mathrm{Pa}$ parent as ${}^{238}\mathrm{Th}.$ The half-life of ${}^{238}\mathrm{Th}$ has been determined to be $9.4\pm 2.0\hspace{0.5em}\min .$ At the same time, a new $\gamma$ ray of $89.0\pm 0.3\hspace{0.5em}\mathrm{KeV}$ was found in the $\gamma$ spectrum gated with $K{\alpha }_1$ x rays of Pa and tentatively assigned to ${}^{238}\mathrm{Th}$ decay.

This work presents results from an ${(e,e}^{\prime }{\alpha }_0)$ experiment in ${}^{26}\mathrm{Mg}.\mathrm{}$ The ${\alpha }_0$ decay branch of the GDR exhibits a small strength, as compared with the statistical expectation, and a large transition radius. Those characteristics suggest that only a fraction of the nuclear charge (close to the surface) participates in the process that leads to the $\alpha$ decay to the ground state of ${}^{22}\mathrm{Ne}.\mathrm{}$

Angular distributions of tritons emitted in the reaction ${}^7\mathrm{Li}(\gamma ,t)\alpha$ have been measured for two photon energy intervals (6.4–6.7 and 8.5–9.0 MeV), and ${\theta }_t$ between $30°$ and $150°.$ Monochromatic photons from neutron capture reactions of the IPEN/CNEN-SP IEA-R1 research reactor were used. The measured data were analyzed in the framework of an $\alpha$-cluster model for the ${}^7\mathrm{Li}$ structure. Results are in good agreement with a recent measurement of the azimuthal cross section asymmetry.

We report on a series of precisely calibrated measurements of the 1157-keV gamma-ray emission rate from the decay of a single source of ${}^{44}\mathrm{Ti}.$ These data were collected over a period of 20 years. We obtain a half-life of $60.7\pm 1.2$ years.

After a brief review of the role three-nucleon forces play in the few-nucleon systems, the chiral-perturbation-theory approach to these forces is discussed. Construction of the (nominal) leading- and subleading-order Born terms and pion-rescattering graphs contributing to two-pion-exchange three-nucleon forces is reviewed, and comparisons are made of the types of such forces that are used today. It is demonstrated that the short-range c term of the Tucson-Melbourne force is unnatural in terms of power counting and should be dropped. The class of two-pion-exchange three-nucleon forces then becomes rather uniform.

The spin-orbit splitting of resonant states in the ${}^4\mathrm{He}+n$ system is investigated by using the complex scaling method (CSM). The calculated energy difference between the $p_{3/2}$ and $p_{1/2}$ states is very small, which is inferred by the R-matrix analyses, though the spin-orbit potential employed for the ${}^4\mathrm{He}-n$ system is strong for the bound states. Furthermore, we show that the calculated energy difference between the $p_{3/2}$ and $p_{1/2}$ states is not the same as the energy difference of the expectation value of the spin-orbit potential; those of the kinetic energy and the central potential are also needed for explanation of the energy difference between the $p_{3/2}$ and $p_{1/2}$ states. To clarify this, we calculate the complex expectation values of the operators in the ${}^4\mathrm{He}-n$ Hamiltonian for the $p_{3/2}$ and $p_{1/2}$ resonant states with a new method recently developed in the framework of the CSM.

The width of the ${}^{12}\mathrm{O}$ ground state is calculated, using $R$-matrix formulas for one-proton sequential decay through the ground state of ${}^{11}\mathrm{N}$ to the ${}^{10}\mathrm{C}$ ground state. From simple models for the ${}^{12}\mathrm{O}$ and ${}^{11}\mathrm{N}$ states, upper limits are placed on the reduced widths for the two decays, giving an upper limit on the ${}^{12}\mathrm{O}$ width that is less than about 100 keV. It is suggested that the available experimental data may not be inconsistent with this limit.

It has been argued that the role of nuclear couplings in the breakup of neutron-rich weakly bound radioactive beams cannot be neglected. In many instances nuclear breakup should be, in fact, the dominant process responsible for projectile fragmentation. It is thus somewhat puzzling that earlier calculations relying only on the electromagnetic processes did not immediately exhibit their inadequacy. We exploit the case of the reaction ${}^{11}\mathrm{Be}$ on ${}^{208}\mathrm{Pb}$ to advance a possible explanation for this apparent discrepancy.

The Bethe-Salpeter equation for the pion in chiral symmetric models is studied with a special care to consistency with low-energy relations. We propose a reduction of the rainbow Schwinger-Dyson and the ladder Bethe-Salpeter equations with a dressed gluon propagator. We prove that the reduction preserves the Ward-Takahashi identity for the axial-vector current and the PCAC relation.

Recent shell model calculations using a realistic interaction by Andreozzi et al. [Phys. Rev. C 56, R16 (1997)] have given excellent agreement with the experimental level spectra of ${}^{134}\mathrm{Te}$ and ${}^{135}\mathrm{I}.$ In addition, these authors call into question our contention that there is a serious inconsistency in the measured masses of N=82 isotones near ${}^{132}\mathrm{Sn}.$ In this Comment, we outline the shell model decomposition method and defend our conclusion that the accepted ground state masses of ${}^{134}\mathrm{Te}$ and/or ${}^{133}\mathrm{Sb}$ must be inaccurate by much more than their assigned errors.

We reply to the preceding Comment.

An article by Williams et al. fails to find evidence for critical behavior in central collisions of 35–400 MeV/nucleon ${}^{84}\mathrm{Kr}{+}^{197}\mathrm{Au}.$ On this basis, and because of the effect of secondary decay on the fragment charge distribution, these authors question the validity of the critical exponents obtained by the EOS Collaboration for 1 GeV/nucleon Au+C. It is shown that the experiment by Williams et al. was not optimized to search for critical behavior and that the effect of secondary decay at the excitation energy corresponding to the critical point in the Au + C system is small.

We reply to the preceding Comment.