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The design, construction, and performance of a segmented-target, cathode-strip, tracking-detector is discussed. The chamber was made of low- Z materials in order to allow photons to leave the target region. It was used to determine the reaction vertex of stopping kaons, and was successfully operated in a high-intensity kaon beamline at the Alternating Gradient Synchrotron at Brookhaven National Laboratory. The vertical and horizontal resolutions of the stopping kaon reaction positions were σ X ∼0.454 mm and σ Y ∼1.180 mm , respectively. The uncertainty in the longitudinal ( Z ) direction is given by one-half the thickness of a target segment.

We present zero-degree differential cross sections and transverse spin-transfer coefficients D{sub NN}(0{degree}) for the {sup 17,18}O({rvec p},{rvec n}){sup 17,18}F reactions at E{sub p}=118 MeV. For the transition to the {sup 17}F(g.s.) to which several multipoles contribute, the measured D{sub NN}(0{degree})={minus}0.13{plus_minus}0.05 is used to separate the Fermi and Gamow-Teller contributions at 0{degree}. The empirical Gamow-Teller strengths and the Fermi strengths are employed to estimate the solar neutrino absorption cross section in {sup 17}O and {sup 18}O. {copyright} {ital 1999} {ital The American Physical Society}

Double-differential cross sections and analyzing powers A{sub y} for the ({rvec p},n) reactions on {sup 3}He and {sup 4}He were measured at 200 MeV between {theta}{sub lab}=0{degree} and 44{degree}. The neutron spectra from {sup 3}He({rvec p},n) are dominated by the quasifree scattering peak and show no evidence for resonances in the three-proton system. The spectra from {sup 4}He({rvec p},n) exhibit strong resonance behavior in the p{sup 3}He system at low relative p{sup 3}He energies owing to the excitation of known L=1 resonances in {sup 4}Li, but there is no distinct quasifree peak in the measured spectra. The experimental A{sub y} for {sup 3}He({rvec p},n), averaged over the experimental range of neutron energies, are similar to those for free nucleon-nucleon (NN) scattering, whereas for {sup 4}He({rvec p},n) the A{sub y} are generally larger than the free values. The cross sections at far forward angles for both {sup 3}He and {sup 4}He appear to be suppressed relative to the free {ital NN} cross sections by Pauli blocking. At most angles, the shapes of the cross section spectra from both {sup 3}He and {sup 4}He are reproduced by distorted-wave impulse approximation (DWIA) calculations using a quasifree scattering model. Specifically for {sup 4}He({rvec p},n),more » the model requires the use of an optical potential which has a strong L=1 potential resonance corresponding to the low-lying L=1 states in {sup 4}Li. {copyright} {ital 1998} {ital The American Physical Society}« less

Asymmetries ${A}_{y}$ for ${\ensuremath{\pi}}^{+}$ and ${\ensuremath{\pi}}^{\ensuremath{-}}$ elastic scattering from polarized ${}^{3}$He were measured at incident energies passing through the $\ensuremath{\pi}$ nucleon ${P}_{33},$ or $\ensuremath{\Delta}$(1232), resonance. The data were taken at the Clinton P. Anderson Meson Physics Facility using the high-energy pion channel ${P}^{3}$ and a large acceptance spectrometer to detect the scattered pions. The polarized ${}^{3}$He target, originally developed at TRIUMF, was modified for these experiments by the addition of diode lasers. Completely unexpected negative asymmetries were observed at and below the resonance in ${\ensuremath{\pi}}^{+}$ scattering near $50\ifmmode^\circ\else\textdegree\fi{}$--60$\ifmmode^\circ\else\textdegree\fi{}$, which cannot be reproduced by multiple scattering theory and Faddeev wave functions. A hybrid model, which adds a $\ensuremath{\Delta}$-neutron spin-spin interaction term to the conventional calculations, provides a good description of the ${\ensuremath{\pi}}^{+}$ data. For ${\ensuremath{\pi}}^{\ensuremath{-}}$ scattering this term predicts a negligible effect on ${A}_{y}$ and the data do not show the anomalous ${A}_{y}$ seen with ${\ensuremath{\pi}}^{+}$.

Cross sections for the {sup 4}He({ital p},{ital p}{sup {prime}}{ital t}) and ({ital p},{ital p}{sup {prime}}{ital h}) reactions have been measured at a bombarding energy of 101.2 MeV. Interpreted within a resonance excitation and decay model, the measurements permit a study of charge-symmetric single-nucleon decays of {sup 4}He resonances. Measured angular correlations indicate that most of the yield arises from the excitation of the generalized dipole response. The results are consistent with minimal isospin mixing in the region of the dipole resonance.

The 17,18 O(p, n) 17,18 F reactions were studied at E p = 35 MeV. Neutron spectra were measured at laboratory angles between 0° and 140°. Results were compared with distorted-wave calculations using the shell-model wave functions. For the 17 O(p, n) reaction, cross-section magnitudes as well as the angular-distribution shapes were well described by the calculation. On the other hand, normalization factors of 0.60 were required for the spin-flip excitations observed in the 18 O(p, n) reaction leading to the ground (1 + ), 1.700 MeV (1 + ) and 2.100 MeV (2 − ) states. Possible origins of such differences were discussed.

A new development in polarized nuclear-target technology has made it possible to measure analyzing power, Ay, in pion elastic scattering from a polarized target.[1] Such measurements provide us with information on the isoscalar spin-flip strength of the nuclear transition which is very difficult to obtain otherwise. Differential cross sections, σ(Θ), for pion elastic scattering from nuclei with non-zero spin are dominated by the spin-independent (∆S = 0) amplitudes. Contributions from the spin-dependent (∆S = 1) amplitudes are usually negligible because σ(Θ) depends on the sum of the squares of those amplitudes. However, the Ay depend on the interference on the spin-independent and spin-dependent scattering amplitudes and are therefore quite sensitive to the spin-dependent forms.

Angular correlation functions for the {sup 4}He({pi}{sup {plus minus}},{pi}{sup {plus minus}{prime}}{ital t}){ital p} reaction at the incident energy {ital T}{sub {pi}}=180 MeV and at four pion scattering angles have been measured. The {sup 4}He({pi}{sup {plus minus}},{pi}{sup {plus minus}{prime}}{ital t}){ital p} data complement previous {sup 4}He({pi}{sup {plus minus}},{pi}{sup {plus minus}{prime}}{ital p}){ital t} results by greatly extending the available range of proton emission angles. We calculate angular correlation functions of the cross sections with three different quasifree knockout models, and we show that direct triton knockout is crucial to an understanding of the data.

Inclusive and exclusive spectra of the {sup 4}He({pi},{pi}{prime},{ital p}) reaction were measured with {pi}{sup +} and {pi}{sup {minus}} at {ital T}{sub {pi}}=140 MeV and {theta}{sub {pi}}=40{degree}, and at 180 MeV and 30{degree}, 40{degree}, 60{degree}, and 80{degree} using the EPICS system at LAMPF in coincidence with elastic plastic scintillators. The inclusive spectra yield cross section ratios {ital R}{sub {pi}}={sigma}({pi}{sup +})/{sigma}({pi}{sup {minus}})=1.1{plus minus}0.1 at both {ital T}{sub {pi}} and all {theta}{sub {pi}}. Exclusive spectra were obtained between {sup 4}He{sup *} excitation energies {ital E}{sub {ital x}}=21.5 and 45.0 MeV. Angular correlation functions for ({pi},{pi}{prime},{ital p}) were extracted at {ital T}{sub {pi}}=180 MeV at the four pion angles for selected regions of {ital E}{sub {ital x}}. The ({pi}{sup +},{pi}{sup +{prime}}{ital p}) angular correlations show a distinct peak near the free proton knockout angle; however, the ({pi}{sup {minus}},{pi}{sup {minus}{prime}}{ital p}) data show either a flat distribution or a mininum near that angle. Calculations, using a distorted wave impulse approximation (DWIA) code which models the ({pi},{pi}{prime}{ital p}) reaction as a pion-induced proton knockout, predict peaks in the angular correlation functions in the quasifree knockout direction and reproduce quite well the ({pi}{sup +},{pi}{sup +{prime}}{ital p}) data above {ital E}{sub {ital x}}=30 MeV. However, these calculations domore » not resemble the ({pi}{sup {minus}},{pi}{sup {minus}{prime}}{ital p}) data at any excitation energy.« less

Inclusive $^{4}\mathrm{He}$(p\ensuremath{\rightarrow},p') spectra were measured at incident energies ${\mathit{T}}_{\mathit{p}}$=500 and 800 MeV over a range of forward scattering angles between 5\ifmmode^\circ\else\textdegree\fi{} and 30\ifmmode^\circ\else\textdegree\fi{}. The first excited ${0}^{+}$, T=0 state at 20.1 MeV and the ${2}^{\mathrm{\ensuremath{-}}}$, T=0 state at 22.1 MeV appear as distinct structures in the spectra. Angular distributions of differential cross sections \ensuremath{\sigma} and analyzing powers ${\mathit{A}}_{\mathit{y}}$ were extracted for these states and for regions of excitation in the continuum up to 40 MeV. Distorted-wave calculations for inelastic scattering using transition densities from the recoil corrected continuum shell model (RCCSM) were compared with the data. The RCCSM generally predicts too small \ensuremath{\sigma} and too large ${\mathit{A}}_{\mathit{y}}$. Assuming a pure giant monopole excitation for the 20.1-MeV, ${0}^{+}$ state, we found greater giant monopole resonance strength than has been deduced from $^{4}\mathrm{He}$(e,e') studies.

Results of the first pion single-charge-exchange experiment on a polarized nuclear target are reported. Analyzing powers {ital A}{sub {ital y}} for the ({pi}{sup +},{pi}{sup 0}) reaction at {ital T}{sub {pi}}{sup +}=163 MeV on a polarized {sup 13}C target were measured over an angular range between 20{degree} and 60{degree} in the laboratory system. Calculations in the distorted-wave impulse approximation do not reproduce these new data.

Analyzing powers {ital A}{sub {ital y}} were measured for {pi}{sup +} and {pi}{sup {minus}} elastic scattering from polarized {sup 13}C at energies near the {ital P}{sub 33} resonance. At {ital T}{sub {pi}}=132 MeV the values of {ital A}{sub {ital y}} are significantly different from zero for {pi}{sup {minus}}. For {pi}{sup +} at 132 MeV and for both {pi}{sup {minus}} and {pi}{sup +} at all other energies, the {ital A}{sub {ital y}} are mostly consistent with zero. These data differ from the predictions of present pion-nucleus reaction theories, especially at large momentum transfers.

Exclusive $^{4}\mathrm{He}$(${\mathrm{\ensuremath{\pi}}}^{\ifmmode\pm\else\textpm\fi{}}$,${\mathrm{\ensuremath{\pi}}}^{\ifmmode\pm\else\textpm\fi{}}$'p${)}^{3}$H spectra in the excitation energy range between 21.5 and 44 MeV in $^{4}\mathrm{He}$ were measured at ${\mathit{T}}_{\mathrm{\ensuremath{\pi}}}$=180 MeV at several pion and proton angles. The cross section ratio ${\mathit{R}}_{\mathrm{\ensuremath{\pi}}\mathit{p}}$=\ensuremath{\sigma}(${\mathrm{\ensuremath{\pi}}}^{+}$,${\mathrm{\ensuremath{\pi}}}^{+}$'p)/\ensuremath{\sigma}(${\mathrm{\ensuremath{\pi}}}^{\mathrm{\ensuremath{-}}}$,${\mathrm{\ensuremath{\pi}}}^{\mathrm{\ensuremath{-}}}$'p) was found to be between 1 and 2 near 22 MeV which is in the region of the ${\mathit{J}}^{\mathrm{\ensuremath{\pi}}}$=${2}^{\mathrm{\ensuremath{-}}}$, T=0 state. Between 25 and 40 MeV in the continuum, which comprises the giant dipole resonance and broad ${2}^{\mathrm{\ensuremath{-}}}$ and ${2}^{+}$ states, ${\mathit{R}}_{\mathrm{\ensuremath{\pi}}\mathit{p}}$ ranges from 0.22 to 45 in sharp contrast to the predicted values of \ensuremath{\approxeq}1 from a model assuming the entire yield is due to the sequential decay of a state of good isospin, and 6 to 9 from a distorted-wave impulse approximation calculation assuming quasifree proton knockout.

The 16O( p , p ′ ) reaction was studied with a 35 MeV polarized proton beam. The cross sections and analyzing powers for excited states in 16O up to and including the 2−, T = 1 state at 12.97 MeV were measured and compared with DWBA calculations. Both density-independent and densitydependent effective interactions were used in the calculations. Transition densities calculated using shell-model amplitudes and Woods-Saxon single-particle wave functions give poor accounts of the data. The use of macroscopic transition densities obtained from electron scattering data give a much better description of the data, especially when used in combination with the densitydependent interaction.

Angular distributions of neutrons from the 208Pb( pi +or-, pi +or-'n) reaction near the giant-resonance region have been measured at Tpi =180 MeV. The neutrons arising from pi - inelastic scattering show evidence of peaking near the quasi-free recoil direction in contrast to those arising from pi +. This observation may be explained by a direct neutron-decay width for the giant resonances that is large when they are excited in ( pi -, pi -') and small in ( pi +, pi +'). Consequences of this suggestion for the analysis of inelastic scattering to the continuum are examined.

A pioneering experiment in {lambda} hypernuclear spectroscopy, undertaken at the Thomas Jefferson National Accelerator Facility (J Lab), was recently reported. The experiment used the high precision, continuous electron beam at JLab, and a special arrangement of spectrometer magnets to measure the hypernuclear spectrum from C and {sup 7}Li targets using the (e,e'K{sup +}) reaction. The {sub {lambda}}{sup 12}B spectrum found in this investigation was previously published, but is reported here in more detail, with improved resolution. In addition, the results of a {sub {lambda}}{sup 7}He spectrum also obtained in the experiment, are shown. This latter spectrum indicates the need for a more detailed few-body calculation of the hypernucleus and the reaction process. The success of the experiment demonstrates the potential of the (e,e'K{sup +}) reaction for high resolution spectroscopy of hypernuclear spectra.

An experimental technique for single‐Λ spectroscopy of the light and medium‐heavy mass Λ‐hypernuclei developed at the Jlab by the E01‐011 Collaboration has been described. The technique is based on the electroproduction of Λ‐hypernuclei by the (e,e′K+) reaction and newly constructed 2nd generation high resolution large solid angle kaon spectrometer (HKS).

Double-differential cross sections ${d}^{2}\ensuremath{\sigma}∕(d\ensuremath{\Omega}d{E}_{x})$ and spectra of analyzing powers, ${A}_{y}$, for the $^{4}\mathrm{He}(\stackrel{P\vec}{p},n)$ reaction were measured at ${T}_{p}\ensuremath{\approx}100$ and $200\phantom{\rule{0.3em}{0ex}}\text{MeV}$ at forward angles between ${\ensuremath{\theta}}_{lab}=0\ifmmode^\circ\else\textdegree\fi{}$ and $44\ifmmode^\circ\else\textdegree\fi{}$, and were analyzed using wave functions from the recoil-corrected continuum shell model (RCCSM). The steep rise of the cross-section spectra just above the $p+^{3}\mathrm{He}$ rest energy threshold results from the excitation of the ${2}^{\ensuremath{-}}$ and ${1}^{\ensuremath{-}}$ resonances in $^{4}\mathrm{Li}$ and is well reproduced by the RCCSM at both incident energies. At higher excitation energies, the predicted cross sections fall off faster than the experimental values at forward angles. The absolute cross sections from the RCCSM were renormalized by factors of 1.3 and 1.6 at $100\phantom{\rule{0.3em}{0ex}}\text{MeV}$ and $200\phantom{\rule{0.3em}{0ex}}\text{MeV}$, respectively, in order to fit the cross section summed over the lowest $10\phantom{\rule{0.3em}{0ex}}\text{MeV}$ of excitation at the peak of the angular distribution. The $100\phantom{\rule{0.3em}{0ex}}\text{MeV}$ ${A}_{y}$, averaged over the lowest $10\phantom{\rule{0.3em}{0ex}}\text{MeV}$ of excitation, are well reproduced by the RCCSM but not the $200\phantom{\rule{0.3em}{0ex}}\text{MeV}$ ${A}_{y}$, nor are the details of the ${A}_{y}$ spectra well described at either energy.

The (Kstopped−,π0) strangeness and charge changing reaction was investigated by producing a BΛ12 hypernucleus from a carbon target. The branching ratio for K− capture to the ground and p-shell states of this hypernucleus was found to be (0.28±0.08)×10−3 and (0.35±0.09)×10−3, respectively, which after correction for isospin was lower than a previously measured value for the C12(Kstopped−,π−)CΛ12 reaction, but still above the theoretical predictions for the ground state. The experiment obtained a missing-mass resolution comparable to in-flight reactions, however the higher background and lower selectivity of the Kstopped− reaction limits its usefulness in the study of new hypernuclear species.

High energy CW electron beams at new accelerator facilities allow electromagnetic production and precision study of hypernuclear structure, and we report here on the first experiment demonstrating the usefulness of the (e,e'K+) reaction. This experiment is also the first to take advantage of the enhanced virtual photon flux available when electrons are scattered at approximately zero degrees. The observed resolution, ~900 keV, of the 12B(hypernuclear) spectrum is the best yet attained using magnetic spectrometers. The positions of the major excitations are in agreement with theoretical predictions and the previous binding energy measurements.

Research in experimental nuclear physics was done from 1979 to 2002 primarily at intermediate energy facilities that provide pion, proton, and kaon beams. Particularly successful has been the work at the Los Alamos Meson Physics Facility (LAMPF) on unraveling the neutron and proton contributions to nuclear ground state and transition densities. This work was done on a wide variety of nuclei and with great detail on the carbon, oxygen, and helium isotopes. Some of the investigations involved the use of polarized targets which allowed the extraction of information on the spin-dependent part of the triangle-nucleon interaction. At the Indiana University Cyclotron Facility (IUCF) we studied proton-induced charge exchange reactions with results of importance to astrophysics and the nuclear few-body problem. During the first few years, the analysis of heavy-ion nucleus scattering data that had been taken prior to 1979 was completed. During the last few years we created hypernuclei by use of a kaon beam at Brookhaven National Laboratory (BNL) and an electron beam at Jefferson Laboratory (JLab). The data taken at BNL for a study of the non-mesonic weak decay of the A particle in a nucleus are still under analysis by our collaborators. The work at JLab resulted in the best resolution hypernuclear spectra measured thus far with magnetic spectrometers.

High-energy, cw electron beams at new accelerator facilities allow electromagnetic production and precision study of hypernuclear structure, and we report here on the first experiment demonstrating the potential of the (e,e'K+) reaction for hypernuclear spectroscopy. This experiment is also the first to take advantage of the enhanced virtual photon flux available when electrons are scattered at approximately zero degrees. The observed energy resolution was found to be approximately 900 keV for the (12)(Lambda)B spectrum, and is substantially better than any previous hypernuclear experiment using magnetic spectrometers. The positions of the major excitations are found to be in agreement with a theoretical prediction and with a previous binding energy measurement, but additional structure is also observed in the core excited region, underlining the future promise of this technique.

The first experiment in Lambda-hypernuclear spectroscopy using the high precision electron beam at Jefferson laboratory (Jlab) has been carried out. The hypernuclear spectrometer system (HNSS) was used to measure spectra from the {sup 12}C(e, e{prime}K{sup +}){sup 12}{sub {Lambda}}B reaction with sub-1 MeV resolution, the best energy resolution obtained thus far in hypernuclear spectroscopy with magnetic spectrometers. This paper describes the HNSS and the preliminary results for the {sup 12}{sub {Lambda}}B system. The experimental spectrum is consistent with the expected strong spin-flip excitations of unnatural parity states. A program of hypernuclear physics experiments is planned for the future with much higher yield and even better energy resolution.

Asymmetries for the ({pi}{sup {minus}},{pi}{sup 0}) reaction on polarized {sup 3}He were measured using a 200-MeV pion beam at LAMPF. The {pi}{sup 0}{close_quote}s were detected with the neutral meson spectrometer in coincidence with the recoiling tritons. A recoil triton detector, consisting of scintillation-counter telescopes and a wire chamber, was used to measure the time-of-flight, energy loss, and direction of the tritons. The polarized gaseous {sup 3}He target, developed at TRIUMF, was modified to run with two diode lasers; the polarization reached 65{percent}. The asymmetries between {theta}{sub lab}=60{degree} and 105{degree} were found to be strongly angle dependent. The results are compared with theoretical calculations. {copyright} {ital 1999} {ital The American Physical Society}

We report on the measurement of differential cross sections and analyzing powers for the inclusive 3,4He(p↘,n) reactions at incident proton energies of Tp=100 and 200 MeV. The data are compared to predictions using several different models.

{pi}-meson and proton beams from the Los Alamos Meson Physics Facility (LAMPF) and the Indiana University Cyclotron Facility (IUCF) were used in scattering and reaction experiments on atomic nuclei. The experimental data allow tests of models of the reaction mechanism and of nuclear structure. For example, the asymmetries observed in a pion scattering experiment on polarized {sup 13}C nuclei were found to contain unique information on the isoscalar spin density. However, further experiments on polarized nuclei of simpler structure are needed to provide the data for a thorough analysis of the reaction mechanism. For this reason a pion scattering experiment on a polarized {sup 3}He target is planned and a high-resolution study on {sup 6}Li({pi},{pi}{prime}) will be done. An analysis of {pi}-triton coincidence events from the {sup 4}He({pi},{pi}{prime}t)p reaction yielded evidence for direct triton knock-out from {sup 4}He. This work will be continued at higher incident pion energies. Additional work on the {sup 4}He(p,n) reaction at IUCF is planned to determine the isovector strength in mass-4 nuclei and the level parameters of {sup 4}Li.

The energy dependences of the spin-dependent and spin-independent free πN interaction are examined using updated πN phase shifts over a wide range of energies. PWIA and DWIA calculations for the purely spin-dependent transition to the 9/2+ state in 13C (9.5 MeV) are used to determine the modifications of this energy dependence by the π-nuclear distortions. It is concluded that the nature of the πN interaction in nuclei should be studied at energies where the absorption is smaller than at the (3,3) resonance. Calculations are also presented for cross sections and asymmetries of elastic scattering of pions from polarized 3He at incident energies T π between 100 and 500 MeV.

Calculations of cross sections and asymmetries for pion elastic scattering on polarized 13C are presented. Transition density amplitudes from different nuclear structure models are used to demonstrate the strong sensitivity of the asymmetry to the nuclear structure details. None of the models reproduces the recent data satisfactorily.

Cross sections of the /sup 40/Ca(/sup 15/N,/sup 16/O)/sup 39/K reaction were measured and analyzed. The transition of the 9/2/sup -/ state, which is of weak-coupling nature, is shown to provide an excellent test of coupled-channel Born-approximation theory and the coupled-channel Born-approximation theory analysis for the L = 1 problem in the /sup 40/Ca(/sup 13/C,/sup 14/N reaction. Calculated two-step contributions to the L = 1 transitions in the (/sup 15/N,/sup 16/O) reaction are large enough to affect the phases of their angular distributions.

Cross sections for ${\ensuremath{\pi}}^{+}$ and ${\ensuremath{\pi}}^{\mathrm{\ensuremath{-}}}$ elastic and inelastic scattering to states in $^{15}\mathrm{N}$ have been measured at an incident pion energy of 164 MeV. Transitions to states at 10.7, 12.5, 14.0, and 17.2 MeV were found to contain significant M4 strength. The M4 assignments are supported both by angular distribution shapes and by additional ${\ensuremath{\pi}}^{+}$ cross sections measured at 120 and 260 MeV. The angular distributions are compared with distorted-wave impulse-approximation calculations to extract isoscalar and isovector spectroscopic amplitudes. These amplitudes are compared with model predictions.

Angular distributions for the elastic and inelastic scattering of 0.8 GeV protons from /sup 24/Mg and /sup 26/Mg are presented. Cross sections for protons exciting states of energy up to about 10 MeV are measured using a high resolution spectrometer. Coupled channels analyses of scattering data to the 0/sup +/, 2/sup +/, 4/sup +/, and 6/sup +/ states in the ground state rotational band, the 2/sup +/, 3/sup +/, 4/sup +/, and 6/sup +/ states in the ..gamma..-vibrational band, the 0/sup +/, 2/sup +/, and 4/sup +/ states in the ..beta..-vibrational band, and the 3/sup -/ and 5/sup -/ members of the K/sup ..pi../ = 0/sup -/ and 3/sup -/ vibrational bands in /sup 24/Mg are presented. Also reported are coupled channels analyses of the experimental angular distributions in /sup 26/Mg for the 0/sup +/, 2/sup +/, and 4/sup +/ states in the ground state band, the possible 2/sup +/, 3/sup +/, and 4/sup +/, ..gamma..-band members, and several 3/sup -/ members of K/sup ..pi../ = 0/sup -/ and 3/sup -/ bands. The data for the 3/sup -/ states in both /sup 24/Mg and /sup 26/Mg differ both in shape and angular positions of the maxima and minima. Coupled channelsmore » analyses are able to account for these differences in the 3/sup -/ experimental cross sections by selecting K/sup ..pi../ = 0/sup -/ or 3/sup -/. This is believed to be the first observation of ''K dependence'' for l = 3 excitations in inelastic scattering by s-d shell nuclei. Distorted wave Born approximation analyses of the other states in /sup 26/Mg excited by l transfers from 2 to 4 are also described. Several new assignments of J/sup ..pi../ for excited states in /sup 26/Mg are proposed based upon the distinctive l transfer dependence found in the positions of the first maximum and in the general shapes of the angular distributions. Multipole moments extracted from the deformed optical potentials are related to those of the matter distributions by Satchler's theorem. These are compared to multipole moments obtained from analyses of hadronic scattering data, as well as with the moments of the charge distributions determined by electromagnetic measurements.« less

Differential cross sections ${\ensuremath{\sigma}}_{{\ensuremath{\pi}}^{\ifmmode\pm\else\textpm\fi{}}}(\ensuremath{\theta})$ for elastic and inelastic scattering of 162-MeV pions from $^{13}\mathrm{C}$ were measured at momentum transfers between 0.6 and 2.1 \ensuremath{\Elzxh} \ifmmode\cdot\else\textperiodcentered\fi{} ${\mathrm{fm}}^{\ensuremath{-}1}$. For two inelastic transitions, enhancement of ${\ensuremath{\sigma}}_{{\ensuremath{\pi}}^{\ensuremath{-}}}$ over ${\ensuremath{\sigma}}_{{\ensuremath{\pi}}^{+}}$ and of ${\ensuremath{\sigma}}_{{\ensuremath{\pi}}^{+}}$ over ${\ensuremath{\sigma}}_{{\ensuremath{\pi}}^{\ensuremath{-}}}$ were observed which are consistent with the values for pion scattering from free nucleons. The results are discussed qualitatively in terms of simple shell-model and weak-coupling-model configurations.

The structure of the 20 O nucleus was studied by the 18 O( 18 O, 16 O) 20 O reaction at E 1ab = 52 MeV. Angular distributions for the transitions to the lowest four states in 20 O were obtained and analyzed with finite-range DWBA calculations. Optical potential sets were used which fit the experimental elastic scattering differential cross sections over almost the whole angular range. The two L = 0 transitions to the ground state and the 4.45 MeV state of 20 O populated by the 18 O( 18 O, 16 O) reaction were analyzed with exact finite-range DWBA calculations using microscopic form factors. These calculations underestimate the absolute cross sections by a factor of 11. The relative strength of the two L = 0 transitions is well reproduced in the 18 O( 18 O, 16 O) reaction. However, DWBA calculations for the 18 O(t, p) 20 O reaction overestimated the relative cross sections for the excited 0 + state by a factor of 6. Several model wave functions were tested for the ground-state transition. It was found that the absolute cross sections of the ( 18 O, 16 O) reaction are very sensitive to the mixing of shell-model configurations. The angular distribution shapes are also slightly dependent on the mixing.

Pion-\ensuremath{\gamma} angular correlations have been measured both in and out of the reaction plane for the reaction $^{12}\mathrm{C}$(\ensuremath{\pi},\ensuremath{\pi}'${)}^{12}$${\mathrm{C}}^{\mathrm{*}}$(${2}^{+}$, 4.44 MeV), $^{12}$${\mathrm{C}}^{\mathrm{*}}$${\ensuremath{\rightarrow}}^{12}$C(g.s.)+\ensuremath{\gamma}. Data are presented at a pion momentum transfer of q=0.47 ${\mathrm{fm}}^{\mathrm{\ensuremath{-}}1}$ for incident pion energies of 116, 140, 162, 180, and 226 MeV and at q=0.85 ${\mathrm{fm}}^{\mathrm{\ensuremath{-}}1}$ for energies of 116, 162, and 226 MeV. A detailed description of the experimental setup together with the applied test procedures and of the data analysis is given. The data are compared to predictions of the \ensuremath{\Delta}-hole model and its static limit.

It is shown that the interference of potential scattering and elastic transfer amplitudes can account for the recently observed gross structure in the excitation function for elastic scattering of 16O by 28Si at 180°.

Differential cross sections for ..pi../sup + -/ elastic scattering on /sup 14/C at a pion kinetic energy of 164 MeV were measured over the angular range 20/sup 0/--91/sup 0/. A contaminant analysis was performed for the target sample based on the kinematic separation of the elastic scattering peaks and the use of previously measured or calculated elastic cross sections. The data are compared to a newly developed, momentum-space, optical-potential calculation which shows clearly the importance of including Pauli suppression and three-body kinematics in the microscopic scattering description.

Cross sections for elastic and inelastic pion scattering from $^{12}\mathrm{C}$ at 162 MeV at angles from 8\ifmmode^\circ\else\textdegree\fi{} to 32\ifmmode^\circ\else\textdegree\fi{} are presented. Standard static model distorted-wave impulse approximation calculations using realistic form factors show large disagreement with the forward angle data for elastic scattering and for exciting both the ${2}_{1}^{+}$ and ${0}_{2}^{+}$ states.

Differential cross sections for $^{13}\mathrm{C}$ ($\ensuremath{\pi}$,${\ensuremath{\pi}}^{\ensuremath{'}}$) were measured between 100 and 300 MeV for momentum transfers of $1.1\ensuremath{\hbar}$ ${\mathrm{fm}}^{\ensuremath{-}1}$ and $1.4\ensuremath{\hbar}$ ${\mathrm{fm}}^{\ensuremath{-}1}$. In this energy range the different energy dependences of the spin-dependent and spin-independent parts of the pion-nucleon interaction provide a very sensitive method of discriminating between transitions that proceed with a spin transfer ($\ensuremath{\Delta}S=1$) or without a spin transfer ($\ensuremath{\Delta}S=0$). Five transitions in $^{13}\mathrm{C}$ were found to be dominated by the $\ensuremath{\Delta}S=1$ transition density amplitude.

The 12 C (π,π′γ) 12 C ∗ (2 + , T=0,4.44 MeV ) angular correlation function was measured at Tπ=162MeV. Da taken in the reaction plane for a range of γ-angles at each of two pion angles support recent theoritical predictions using the isobar-hole formalism.

Elastic cross sections have been measured for the scattering of ..pi../sup +/ and ..pi../sup -/ from /sup 16/O at 114 MeV in the angular range of 115/sup 0/ to 175/sup 0/ (c.m.). Large cross sections and large ..pi../sup +//..pi../sup -/ differences have been observed beyond 140/sup 0/ (c.m.). First-order optical model calculations fail to reproduce the large-angle data. Second-order effects generally improve the fits, but the details of the present data together with the results of earlier measurements at smaller angles have not been satisfactorily explained.