We have extended the first-order eikonal model formalism to include charged pions scattering on nuclei. It has been applied satisfactorily to elastic angular distributions of 800 MeV/c pions scattering from ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ and ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ca}$ nuclei. © 1996 The American Physical Society.

We have studied the first-order core-polarization effects in pion single-charge-exchange reactions from polarized ${}_{}{}^{15}{}_{}{}^{}\mathrm{N}$ and ${}_{}{}^{13}{}_{}{}^{}\mathrm{C}$ under the distorted-wave impulse approximation. It is shown that the reaction cross section and also the asymmetry are moderately affected by the core polarization. © 1996 The American Physical Society.

A closed expression for the dynamical polarization potential is obtained starting from the unified reaction theory of Feshbach. This result is compared with a few methods available in the current literature to evaluate the optical potential. Two main features emerging from the comparison are that the propagator in the nonelastic channels is different from the one appearing in iterative approaches and that in the polarization potential the final matrix elements, which recouple the inelastic channels to the elastic channel, are not linear functions of the coupling interaction. © 1996 The American Physical Society.

Gamma-ray coincidence spectra presented by Vo et al. [Phys. Rev. C 50, 1713 (1994)] may indicate the existence of a positron (${\mathit{e}}^{+}$) transition with a maximum decay energy of (15.9±1.2) keV. Possible sources of spurious coincidences, mimicking the ${\mathit{e}}^{+}$ signal, are discussed and, where possible, calculated or estimated. Considerable systematic uncertainty remains in estimating the noise coincidence rate; hence, the existence of this ${\mathit{e}}^{+}$ transition is not established. Another ${\mathit{e}}^{+}$ transition with a maximum decay energy of 243 keV has been identified for the first time. © 1996 The American Physical Society.

Using the spectra in the article ‘‘Very weak γ transitions in the ε/${\mathrm{\beta }}^{+}$ decay of 68 Ga’’ [D. T. Vo et al.. Phys. Rev. C 50, 1713 (1994)], Skalsey makes an interesting speculation in the accompanying article [M. Skalsey, Phys. Rev. C 54, 439 (1996), the preceding paper] on the possible existence of a positron feeding with a kinetic endpoint energy of 16 keV in the decay of ${}_{}{}^{68}{}_{}{}^{}\mathrm{Ga}$. Skalsey also points out the facts supporting the ${\mathit{e}}^{+}$ feeding to the 1656-keV level that were not mentioned by Vo et al. In this Reply to the Comment, we present information supporting the new ${\mathit{e}}^{+}$ decay to the 1656-keV level and further information on the statistical uncertainties that suggest an even greater skepticism than that shown by Skalsey about the possible existence of the 16-keV ${\mathit{e}}^{+}$ decay to the 1883-keV level upon which he commented. © 1996 The American Physical Society.

We demonstrate the feasibility and efficiency of the Coulomb-Sturmian separable expansion method for generating accurate solutions of the Faddeev equations. Results obtained with this method are reported for several benchmark cases of bosonic and fermionic three-body systems. Correct bound-state results in agreement with the ones established in the literature are achieved for short-range interactions. We outline the formalism for the treatment of three-body Coulomb systems and present a bound-state calculation for a three-boson system interacting via Coulomb plus short-range forces. The corresponding result is in good agreement with the answer from a recent stochastic-variational-method calculation. © 1996 The American Physical Society.

The high-spin structure of ${}_{}{}^{139}{}_{}{}^{}\mathrm{Sm}$ has been studied through the ${}_{}{}^{110}{}_{}{}^{}\mathrm{Pd}$${(}^{34}$S,5n) reaction at beam energies of 150 and 165 MeV. The level scheme has been extended up to an excitation energy of 11.1 MeV and spin 61/$2^{+}$. A band built on the ν${\mathit{i}}_{13/2}$ [660]1/$2^{+}$ intruder orbital has been established and firmly linked to the known lower-spin levels in the nucleus. The low-lying states of both parities as well as a relatively strong ΔI=1 regular structure observed above spin 27/$2^{\mathrm{-}}$ are nicely reproduced by the interacting boson-fermion model with broken pairs. © 1996 The American Physical Society.

The region of excitation energy from 7≤${\mathit{E}}_{\mathit{x}}$≤38 MeV in ${}_{}{}^{116}{}_{}{}^{}\mathrm{Sn}$ was studied with inelastic scattering of 240 MeV α particles. Parameters obtained for the isoscalar giant monopole resonance and the isoscalar giant quadrupole resonance are in agreement with accepted values. A peak exhausting (67±10)% of the E3 energy-weighted sum rule at ${\mathit{E}}_{\mathit{x}}$=21.8±0.5 MeV with width Γ=7.1±0.5 MeV was identified as the isoscalar high energy octupole resonance (HEOR). The energy and width are consistent with previous measurements made with proton, ${}_{}{}^3{}_{}{}^{}\mathrm{He}$, and α particle projectiles. The observed strength of the HEOR is in agreement with measurements made with ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ inelastic scattering, but is roughly three to four times larger than measurements made with α particle and proton inelastic scattering. © 1996 The American Physical Society.

We have made experimental measurements in ${}_{}{}^{170}{}_{}{}^{}\mathrm{Tm}$ of the following: secondary γ rays, conversion electrons, and γ-γ coincidences from thermal neutron capture in ${}_{}{}^{169}{}_{}{}^{}\mathrm{Tm}$, primary γ rays from average resonance capture with 2-keV and 24-keV neutron beams, and proton spectra from the (d,p) reaction on ${}_{}{}^{169}{}_{}{}^{}\mathrm{Tm}$. From these data and those of previous investigations, we have identified more than 130 excited levels in ${}_{}{}^{170}{}_{}{}^{}\mathrm{Tm}$ below 1550 keV. Of these, 62 (with connecting transitions) are placed in 18 rotational bands with assigned Nilsson configurations. These results are in good agreement with a semiempirical modeling of ${}_{}{}^{170}{}_{}{}^{}\mathrm{Tm}$ level structure. Values for seven Gallagher-Moszkowski splittings and four Newby shifts have been obtained. These matrix elements show remarkably good agreement with calculation. Among the observed ${\mathit{K}}^{\mathrm{\pi }}$=$1^{\mathrm{-}}$ and $2^{\mathrm{-}}$ rotational bands, configuration mixing appears to play a significant role. © 1996 The American Physical Society.

Gamma-ray measurements following fusion-evaporation reactions have identified in the $N=84\mathrm{}$ isotones from Ho to Yb the complete yrast lines formed by the configurations $\pi h_{\frac{11}{2}}^n\nu f_{\frac{7}{2}}^2$ and $\pi h_{\frac{11}{2}}^n\nu f_{\frac{7}{2}}{h}_{\frac{9}{2}}$ from the nuclear ground states up to their highest spins near $25\hslash$ at 5-8 MeV excitation. Their energies are predicted with high accuracy in parameter-free shell model calculations using experimental one- and two-body matrix elements.

Multifragment emission of charged particles from the ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ca}$ + ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ca}$ reaction at 35 MeV/nucleon has been investigated. Multiplicity as well as event shape filters were used to distinguish nearly central from peripheral collisions. A correlation between higher multiplicities and random events from two reactions occurring in one beam burst is discussed. Signatures of different reaction scenarios are investigated using simulation techniques.

A strangelet search in Si+Pt and Au+Pt collisions at alternating-gradient synchrotron (AGS) energies, using a focusing spectrometer, sensitive to mass per charge of 3-14 GeV/${\mathit{c}}^2$ was conducted during the 1992 and 1993 heavy ion runs at the AGS. The null results thereof are presented as upper limits on the invariant production cross section, in the range of ${10}^{-5\mathrm{}}$-${10}^{-4\mathrm{}}$ mb ${\mathit{c}}^3$/${\mathrm{GeV}}^2$, and model dependent sensitivity limits in the range of ${10}^{-7\mathrm{}}$-${10}^{-5\mathrm{}}$ per collision. Measurements of the production cross sections of several nonstrange nuclear systems, from $p$ to ${}_{}{}^7{}_{}{}^{}\mathrm{Be}$ and ${}_{}{}^8{}_{}{}^{}\mathrm{Li}$, the background of the strangelet search, are also presented.

In a series of ${}_{}{}^{78}{}_{}{}^{}\mathrm{Kr}$ bombardments of ${}_{}{}^{92}{}_{}{}^{}\mathrm{Mo}$ the new isotopes ${}_{}{}^{166}{}_{}{}^{}\mathrm{Pt}$ and ${}_{}{}^{167}{}_{}{}^{}\mathrm{Pt}$ were identified via their $\alpha$-decay properties. The $\alpha$-decay energies and half-lives of these two nuclides are as follows. (1) ${}_{}{}^{166}{}_{}{}^{}\mathrm{Pt}$, $E_{\alpha }=7110\mathrm{}\left(15\right)\mathrm{}$ keV, $T_{\frac{1}{2}}=0.3\mathrm{}\left(1\right)\mathrm{}$ ms, and (2) ${}_{}{}^{167}{}_{}{}^{}\mathrm{Pt}$, $E_{\alpha }=6988\mathrm{}\left(10\right)\mathrm{}$ keV, $T_{\frac{1}{2}}=0.7\mathrm{}\left(2\right)\mathrm{}$ ms. Also, the half-life of ${}_{}{}^{168}{}_{}{}^{}\mathrm{Pt}$, which was previously unknown, was determined to be 2.0(4) ms. In a separate but concurrent experiment involving ${}_{}{}^{78}{}_{}{}^{}\mathrm{Kr}$ + ${}_{}{}^{96}{}_{}{}^{}\mathrm{Ru}$ reactions, ${}_{}{}^{170}{}_{}{}^{}\mathrm{Pt}$ was made and a half-life of 14.7(5) ms was measured for it; the one published value is $6_{-2\mathrm{}}^{+5\mathrm{}}$ ms. Results for ${}_{}{}^{162-164}{}_{}{}^{}\mathrm{Os}$ contained in the same data sets were also analyzed and by using mother-daughter correlations, the $\alpha$ branches of ${}_{}{}^{162,163,164}{}_{}{}^{}\mathrm{Os}$ were established to be near 100%.

Conversion processes for ${}_{\Xi }{}^7{}_{}{}^{}\mathrm{H}$ are discussed as a typical example of the double-$\Lambda$ hypernuclear formation via a neutron-rich $\Xi$ state. ${}_{\Lambda \Lambda }{}^5{}_{}{}^{}\mathrm{H}$ is formed with a surprisingly large branching ratio of about 90% from ${}_{\Xi }{}^7{}_{}{}^{}\mathrm{H}$ that is produced by the ($K^{-}, K^{+}$) reaction on the ${}_{}{}^7{}_{}{}^{}\mathrm{Li}$ target. The ${}_{\Xi }{}^7{}_{}{}^{}\mathrm{H}$ state has a narrow width, 0.75 MeV, and its population can be confirmed by tagging $K^{+}$ momentum.

The fragmentation pattern of central multifragmentation events observed in the collision of heavy systems can be recognized at a time when the system is still dense and the particles are still interacting with each other. This is the result obtained by applying simulated annealing algorithms to molecular dynamics simulations. We employ this algorithm to central and peripheral reactions of heavy nuclei simulated by the quantum molecular dynamics model (QMD). We see that in central collisions the fragments can already be identified when the density is still close to normal nuclear matter density and hence the fragment nucleons never pass through a density sufficiently low to allow for a liquid gas phase transition. In peripheral reactions, however, we observe that shortly after the nuclei have passed each other a division of the spectator matter into several medium-size clusters would yield the highest binding energy. However, the spectator matter does not break into these clusters but approaches thermal equilibrium.

Results are presented from a coincidence study of the ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}(\gamma , {\pi }^{+}n){}_{}{}^{11}{}_{}{}^{}\mathrm{B}$ quasifree pion production reaction made in the $\Delta$-resonance region using tagged photons. Cross sections for reactions originating on $1p$-shell protons are found to be significantly larger than predicted by calculations based on quasifree pion production. It is suggested that more sophisticated calculations, perhaps including medium effects, may be required to reproduce the data.

A formalism, based on an isobaric approach using Feynman diagrammatic techniques, which includes the nucleonic (spin ≤ 5/2), hyperonic (spin 1/2), and kaonic resonances, is developed. Using this formalism, a thorough investigation of the following electromagnetic strangeness processes, for which experimental results are available, is performed: γp→${\mathit{K}}^{+}$Λ, ${\mathit{K}}^{+}$${\mathrm{\Sigma }}^0$, ${\mathit{K}}^0$${\mathrm{\Sigma }}^{+}$, for ${\mathit{E}}_{\gamma }^{\mathrm{lab}}$≤ 2.1 GeV, ep→${\mathit{e}}^{\prime }$${\mathit{K}}^{+}$Λ, ${\mathit{e}}^{\prime }$${\mathit{K}}^{+}$${\mathrm{\Sigma }}^0$, and ${\mathit{K}}^{\mathrm{-}}$p→γΛ,γ${\mathrm{\Sigma }}^0$. A reaction mechanism, describing well enough the data, is found to include a reasonable number of baryonic resonances among a very large number of potential candidates. The extracted main kaon-hyperon-nucleon coupling constants are in good agreement with values predicted using SU(3) symmetry. The main findings of this model are compared with the results of other recent phenomenological studies. Predictions for the upcoming photoproduction polarization and electroproduction observables are presented, and their sensitivity to the phenomenological models ingredients are emphasized. © 1996 The American Physical Society.

Results obtained by solving Alt-Grassberger-Sandhas (AGS)-type integral equations for the photodisintegration of ${}_{}{}^4{}_{}{}^{}\mathrm{He}$, employing the Malfliet-Tjon potential, are compared with the latest experimental data. Good agreement between theory and experiment is found in electric dipole approximation for the total cross section, but the differential cross sections differ at higher energies. This discrepancy is reduced, but not fully removed by taking into account the electric quadrupole contributions. In order to get some feeling for the sensitivity to the underlying potential, we also show calculations based on the Yamaguchi potential. They differ from the Malfliet-Tjon results in a way which resembles the trends known from triton photodisintegration.

We analyzed the general form of all polarization effects in the ${}_{}{}^3{}_{}{}^{}\mathrm{H}$${+}^3$He→${\mathit{d}}^2$H${+}^4$He reaction. For this aim, we parametrized the spin structure of the full amplitude in terms of the transverse amplitudes which describe the different transitions between initial and final states, which in turn are differed by projections of nuclei spins along the normal to the reaction plane. The isospin invariance of the strong interaction generates definite symmetry properties of the transverse amplitudes relative to the change cosθ→-cosθ, where θ is the deuteron production angle in the c.m.s. We found all symmetry relations for the polarization observables in the ${}_{}{}^3{}_{}{}^{}\mathrm{H}$${+}^3$He→${\mathit{d}}^2$H${+}^4$He reaction, which are the generalized form of the well-known Barshay-Temmer theorem. We consider the one-, two-, and triple-spin correlations in ${}_{}{}^3{}_{}{}^{}\mathrm{H}$${+}^3$He→${\mathit{d}}^2$H${+}^4$He. For analysis of the triple-spin correlations, we focus on the structure functions formalism and show that a set of 41 structure functions describes all such correlations. Isospin invariance simplifies the spin structure of the full amplitude at θ=90°; therefore, we calculated all polarization observables for this special kinematics. © 1996 The American Physical Society.

We use power-counting arguments as an organizing principle to apply chiral perturbation theory, including an explicit $\Delta$,to the $\mathrm{pp}\to \mathrm{pp}{\pi }^0$ reaction near threshold. There are two lowest-order leading mechanisms expected to contribute to the amplitude with similar magnitudes: an impulse term, and a $\Delta$-excitation mechanism. We examine formally subleading but potentially large mechanisms, including pion-rescattering and short-ranged contributions. We show that the pion-rescattering contribution is enhanced by off-shell effects and has a sign opposite to that of a recent estimate based on a PCAC pion interpolating field. Our result is that the impulse term interferes destructively with the pion-rescattering and $\Delta$-excitation terms. In addition, we have modeled the short-ranged interaction using $\sigma$ and $\omega$ exchange mechanisms. A recoil correction to the impulse approximation is small. The total amplitude obtained including all of these processes is found to yield cross sections substantially smaller than the measured ones.