Search

Data of the ({pi}{sup +},{pi}{sup {minus}}) reaction on {sup 128}Te and {sup 130}Te at {ital T}{sub {pi}}=48 MeV are presented, which constitute also the first observation of pionic double charge exchange (DCX) on heavy nuclei at energies below the (3,3) resonance. For the ground state transitions in these isotopes we find very small cross sections of about 15 nb/sr only at 30{degree} and a ratio of {sigma}({sup 130}Te)/{sigma}({sup 128}Te)=1.5{sub {minus}0.8}{sup +1.8}. The experimental results and their impact on the understanding of the {beta}{beta} decay of the Te isotopes are discussed within the framework of recent proton-neutron quasiparticle random phase approximation calculations. For the transitions to the double isobaric analog states in {sup 128}Xe and {sup 130}Xe we obtain cross sections in the range 1 {mu}b/sr which fit very well into a systematics, that is in accordance with a dominance of the short-range part of the DCX operator in analog transitions at low pion energies. {copyright} {ital 1996 The American Physical Society.}

Differential cross sections were measured for 50 MeV {pi}{sup +} and {pi}{sup {minus}} elastic scattering from {sup 12}C and for 50 MeV {pi}{sup +} inelastic scattering to the (4.44 MeV, 2{sup +}), (7.65 MeV, 0{sub 2}{sup +}), (9.64 MeV, 3{sup {minus}}), (12.71 MeV, 1{sup +}), and (15.11 MeV, 1{sup +}) levels in {sup 12}C. Comparisons of the data obtained in this study to data taken previously for these states resolve discrepancies between the earlier data sets. Using a recently discussed procedure, one-step and coupled-channels calculations using a modified MSU potential were performed. The results of both one-step and coupled-channels calculations describe the data for the ground, first, and third excited states, indicative of the collective isoscalar structure of those states. The one-step analysis fails to describe the excitation of the 0{sub 2}{sup +} state. The coupled-channels calculations are more successful in describing those data, indicating that the failure of the one-step calculations may be attributed to coupled-channels effects.

We have measured cross sections for the $ (\pi^+,\pi^\pm p)$ reactions on ${\rm ^3H}$, ${\rm ^4He}$, ${\rm ^6Li}$ and ${\rm ^7Li}$ in quasi-free kinematics at incident pion beam energy 500 MeV. An enhancement of the $(\pi^+,\pi^- p)$ cross section in this kinematics is observed. If this is interpreted as due to quasi-free scattering from pre-existing $\Delta$ components of the nuclear wave function, the extracted probabilities are in agreement with theoretical expectations., Comment: 3 pages, 3 figures, 1 table

High quality analyzing powers for the ${\ensuremath{\pi}}^{\ensuremath{-}}\stackrel{\ensuremath{\rightarrow}}{p}\ensuremath{\rightarrow}{\ensuremath{\pi}}^{0}n$ reaction have been obtained with a polarized proton target over a broad angular range at incident kinetic energies of 98.1, 138.8, 165.9, and 214.4 MeV. This experiment nearly doubled the existing $\ensuremath{\pi}N$ single-charge-exchange database for energies ranging from 10 to 230 MeV, with 36 new analyzing powers. The Neutral Meson Spectrometer was used to detect the outgoing neutral pions. The data are well described by recent phase-shift analyses. When combined with high-precision and accurate cross section data at the same energies, the data can provide a good test of the degree of isospin breaking in the region of the $\ensuremath{\Delta}(1232)$ resonance. They will also be helpful for constraining the evaluation of the pion-nucleon $\ensuremath{\sigma}$ term from the scattering amplitudes.

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}

A short‐orbit spectrometer capable of detecting particles with momentum

Differential cross sections for /sup 13/C(..pi../sup + -/,..pi../sup plus-or-minusprime/ )/sup 13/C* were measured at an incident pion energy of 162 MeV. Data were obtained for states or groups of states up to 21.6 MeV in excitation energy. The experimental results are compared with the distorted-wave impulse approximation calculations of Lee and Kurath.

Excitation functions for inelastic scattering of ..pi../sup -/ from /sup 48/Ca to the 1/sup +/ state at 10.2 MeV have been measured at constant momentum transfer q = 73 MeV/c. The incident energy was varied between 116 and 180 MeV. An upper limit was measured for the ..pi../sup +/ cross section at 116 MeV. The data are not fitted by distorted-wave impulse approximation calculations at this q where the differential cross section is predicted to have its maximum. The discrepancy between theory and experiment is similar to the disagreement observed for /sup 12/C(..pi..,..pi..')/sup 12/C(1/sup +/ ,15.1 MeV).

Elastic and inelastic scattering of π + and π − from 7 Li has been studied at 143 MeV on the EPICS system at LAMPF. The comparison of the π − and π + elastic scattering ratio allowed an approximate determination of a neutron matter rms radius of 2.5 fm, compared to 2.39 fm for the charge radius. The π − inelastic yields to the ground-state band members exceed the π + yields by about a factor of 1.25, consistent, within a model of active p-shell nucleons, with the difference in neutron and proton radii obtained from the elastic scattering.

The elastic scattering of 162-MeV ${\ensuremath{\pi}}^{+}$ and ${\ensuremath{\pi}}^{\ensuremath{-}}$ by $^{9}\mathrm{Be}$, Si, $^{58}\mathrm{Ni}$, and $^{208}\mathrm{Pb}$ have been measured. All angular distributions, except for $^{9}\mathrm{Be}$, exhibit strong diffraction patterns. Optical-model calculations with matter distributions deduced from electron scattering qualitatively reproduce the data, but better agreement for all but $^{9}\mathrm{Be}$ can be obtained with suitable modifications. No substantial differences in neutron- and proton-matter radii are indicated.

The isoscalar giant quadrupole resonance is studied in /sup 118/Sn(..pi../sup + -/,..pi../sup + -/') at 130 MeV. It is found that the ratio of ..pi../sup -/ to ..pi../sup +/ cross sections at their maximum is 1.9 and that 57% of the energy-weighted sum rule is exhausted in ..pi../sup -/ scattering. This large ratio of ..pi../sup -/ to ..pi../sup +/ cross sections is not anticipated by conventional models, and may be interpreted as evidence for substantial isovector strength.

A sensitive test of nuclear charge symmetry has been made by comparing differential cross sections for ..pi../sup +/ and ..pi../sup -/ elastic scattering from deuterium at 143 MeV. Residual charge symmetry breaking effects in the cross section ratio have been parametrized in terms of mass and width differences among the components of the ..delta.. isobar. Accurate absolute ..pi../sup -/d differential cross sections were measured for the first time and ..pi../sup +/d differential cross sections agree well with other results and with three-body calculations.

Elastic cross sections for the scattering of positive and negative pions from /sup 58,60,64/Ni were measured at 30 MeV incident pion energy. A clear isotope effect was observed in the ..pi../sup -/ cross sections while no effect was observed in the ..pi../sup +/ cross sections. The cross sections were compared to predictions made by various optical model calculations. In general, both ..pi../sup +/ and ..pi../sup -/ cross sections were poorly described and the ..pi../sup -/ isotope effects were not well reproduced. Anomalous effects first observed in pionic atoms may also appear in the present data.

Elastic cross sections for the scattering of negative pions from /sup 12/C were measured at 19.5 and 30 MeV incident pion energy. At both energies the new cross sections show fair agreement with optical model predictions. At 30 MeV the new cross sections disagree at forward angles with previously measured values, while at 19.5 MeV the data represent the first report of /sup 12/C ..pi../sup -/ scattering at this energy.

The inelastic scattering of 162-MeV pions was studied over the angular range 35/sup 0/ to 100/sup 0/ in the laboratory system and the data were analyzed with a model that incorporates shell-model wave functions into a distorted-wave impulse approximation formalism. Reduced transition probabilities were obtained for low-lying levels and compared with information previously reported. In addition, evidence is obtained for theoretically predicted levels with high spin that have not been observed previously.

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.

$\ensuremath{\gamma}$ radiation from targets of $^{7}\mathrm{Li}$, $^{9}\mathrm{Be}$, $^{12}\mathrm{C}$, $^{13}\mathrm{C}$, and $^{16}\mathrm{O}$ bombarded by ${\ensuremath{\pi}}^{\ensuremath{-}}$ and ${\ensuremath{\pi}}^{+}$ at energies between 60 and 300 MeV was uniquely associated with states formed by removing a single nucleon by the ($\ensuremath{\pi},\ensuremath{\pi}N$) reaction. All yields were found to reflect the well-known 3-3 resonance near 180 MeV in the pion-nucleon system. Ratios of yields for ${\ensuremath{\pi}}^{\ensuremath{-}}$ and ${\ensuremath{\pi}}^{+}$ beams were measured for $^{7}\mathrm{Li}$, $^{9}\mathrm{Be}$, and $^{13}\mathrm{C}$. These ratios were very similar to one another and to previous results on $^{12}\mathrm{C}$, $^{14}\mathrm{N}$, and $^{16}\mathrm{O}$ for neutron removal. Several reaction mechanisms based on quasifree processes are tested by comparison to the data, and all are rejected.

A range-nuclear-interaction absorber for rejecting muons in the focal plane of the EPICS spectrometer is described. This absorber rejects 95% of the muons in the focal plane, while rejecting fewer than 4% of the pions.

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.

The ..gamma..-ray decays of the 9.17-MeV state in /sup 14/N have been remeasured with a Ge(Li) detector. The primary purpose was to obtain an improved value of the M1 decay strength of the (2/sup +/,0) 7.03-MeV state in /sup 14/N. Additional information about the branching ratios and mixing ratios of other states and transitions was also obtained and is tabulated. The measured value of the E2/M1 mixing of the 7.03-MeV..-->..0-MeV transition was 0.74 +- 0.09; this was combined with previous measurements of this ratio and of the branching ratio and total width of the 7.03-MeV state to obtain an M1 transition strength of (86 +- 9) x 10/sup -3/ eV. This strength is then compared with the predictions of various shell model calculations. This analysis suggests the introduction of an effective isoscalar magnetic dipole operator, which is constructed by fitting the ground state magnetic moment of /sup 14/N, as well as the 7.03-MeV..-->..0-MeV transition. This effective operator is then employed to predict the ground state magnetic moments of other nuclei in the 0p and 0s shells, with reasonable success. (AIP)

Differential cross sections for elastic and inelastic scattering of 0.8 GeV protons from /sup 89/Y and /sup 90/Zr have been measured to momentum transfers of 3.8 fm/sup -1/. The results were analyzed in terms of a relativistic nuclear optical model and indicate that the elastic and inelastic scattering are dominated by surface features of the nucleus. The effect of the spin orbit term in the optical potential on the inelastic cross sections appears to be small.

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.

Analyses of 0.8 and 1 GeV $p$+$^{208}\mathrm{Pb}$ elastic angular distribution data have obtained neutron-proton root-mean-square radius differences ($\ensuremath{\Delta}{r}_{\mathrm{np}}$) which are not consistent. Therefore, the 0.8 GeV experiment was repeated using a high resolution spectrometer. The new higher precision data are consistent with the older data, apart from a 15% overall normalization difference. A second order Kerman-McManus-Thaler optical model analysis of the new data, using a model-independent neutron density, yields $\ensuremath{\Delta}{r}_{\mathrm{np}}=0.14\ifmmode\pm\else\textpm\fi{}0.04$ fm, in good agreement with the most recent result obtained (0.16\ifmmode\pm\else\textpm\fi{}0.05 fm) from a similar analysis of the older 0.8 GeV data. In addition, the elastic angular distribution was extended to 42.5\ifmmode^\circ\else\textdegree\fi{} center of mass in order to explore the momentum transfer region from 3.5 to 5.3 ${\mathrm{fm}}^{\ensuremath{-}1}$. Although the familiar diffraction pattern persists to 42.5\ifmmode^\circ\else\textdegree\fi{}, it was not possible within the framework of our application of the Kerman-McManus-Thaler optical model to fit the data even qualitatively at the larger momentum transfers.NUCLEAR REACTIONS $^{208}\mathrm{Pb}$($p$,$p$), $E=0.8$ GeV, measured $\ensuremath{\sigma}(\ensuremath{\theta})$; enriched target; resolution \ensuremath{\simeq} 100 keV, ${\ensuremath{\theta}}_{\mathrm{c}.\mathrm{m}.}=2.5\ifmmode^\circ\else\textdegree\fi{} \mathrm{to} 42.5\ifmmode^\circ\else\textdegree\fi{}$. Microscopic optical model analysis using KMT potential; deduced $\ensuremath{\Delta}{\mathcal{r}}_{\mathrm{np}}$; error analysis and comparison with other results.

Angular distributions for the elastic and inelastic scattering of 162 MeV ${\ensuremath{\pi}}^{+}$ and ${\ensuremath{\pi}}^{\ensuremath{-}}$ by Si, $^{58}\mathrm{Ni}$, and $^{208}\mathrm{Pb}$ have been measured. The elastic scattering data are fitted with optical model calculations in configuration space. Momentum-space optical-model calculations qualitatively reproduce the elastic scattering data, but substantially better agreement can be obtained if suitable modifications to the model are made. Distorted-wave impulse approximation calculations of the inelastic scattering, using both configuration-space and momentum-space models, generally reproduce the experimental data.NUCLEAR REACTIONS $^{28}\mathrm{Si}(\ensuremath{\pi},{\ensuremath{\pi}}^{\ensuremath{'}})$, $^{58}\mathrm{Ni}(\ensuremath{\pi},{\ensuremath{\pi}}^{\ensuremath{'}})$, $^{208}\mathrm{Pb}(\ensuremath{\pi},{\ensuremath{\pi}}^{\ensuremath{'}})$, $E=162$ MeV, measured $\frac{d\ensuremath{\sigma}}{d\ensuremath{\Omega}}$; optical potential and DWIA collective model analyses.

Differential cross sections are reported for ..pi../sup +/+/sup 3,4/He elastic scattering at 260, 295, and 310 MeV and ..pi../sup -/+/sup 3,4/He at 295 MeV. The angular distributions )except for ..pi../sup -/+/sup 3/He) confirm the fixed angle (thetaapprox. =75/sup 0/) minimum seen at lower energies (caused by the (3,3) ..pi..+N resonance dominance) and show a deep minimum at thetaapprox. =110/sup 0/. Comparisons are made to ..pi..+d and the current discussion of pion excitation of intermediate dibaryon and ..delta..N states.

Pion inelastic scattering has been used to extract the off-diagonal charge dependent matrix element, H01, between the Jπ = 1+ doublet of states at 12.71 (T = 0) and 15.11 (T = 1) MeV in 12 C . The reported measurements yield a value, H01 = 148 ±29 keV, in good agreement with recent electromagnetic measurements.

The data acquisition and analysis system for LAMPF'S high resolution magnetic spectrometers, HRS and EPICS, consists of two on-line PDP-11/45 computers and an off-line PDP-11/60 for analysis of taped data. Each system has 124K words of memory and runs under DEC's RSX-11D operating system. The on-line computers are interfaced to several CAMAC crates through a Microprogrammable Branch Driver (MBD). Each system is also equipped with two Tektronix 4010 terminals, a Versatec printer/plotter, at least one RK05 disk drive, a 9 track 75 IPS 800/1600 BPI Kennedy tape drive, and a 40MB Diva/Calcomp disk drive system which is compatible with DEC software for their RP03. The software developed for these systems was designed to meet the goals of flexibility and speed of analysis for multiparameter data (20-100 words/event). The LAMPF standard data aquisition package "O" and its associated routines for histogram management are used as the basis of the system. A number of additional features have been added whose usefulness appears to he common to most experiments of this type.

π+ and π− elastic and inelastic scattering from 18O have been measured at T(π)=164 MeV. Consistent with the results at 230 MeV, it is found that the ratio σ(π − ) σ(π + ) for the 21+ state is 1.86(16), while for the 31− state it is 0.89(6). These results are interpreted as indicating differences in neutron and proton deformations characterizing the 21+ transition and partial neutron blocking for the 31− transition. Optical model analysis of elastic scattering leads to the conclusion that 〈r n 2 〉 1 2 −〈r p 2 〉 1 2 =0.03(3) fm .

A facility has been constructed to extend the measurements of pion-nucleus scattering with the EPICS system at LAMPF into the angular range of 115 to 180°. The design of the system is described, and results of tests on it are given. Comparisons of measurements of elastic scattering cross sections with previous data are presented.

Differential cross sections are reported for (${\ensuremath{\pi}}^{+}$,$p$) reactions to discrete final states over the range $\ensuremath{\theta}=20\ensuremath{-}95 (116\ifmmode^\circ\else\textdegree\fi{})$ and for the inclusive (${\ensuremath{\pi}}^{\ifmmode\pm\else\textpm\fi{}}$,$p$) reactions in $^{6}\mathrm{Li}$ at $\ensuremath{\theta}=20\ifmmode^\circ\else\textdegree\fi{}$ to the continuum. The continuum cross sections indicate the predominance of the two-nucleon pion absorption mechanism where (${\ensuremath{\pi}}^{\ensuremath{-}}$,$p$) shows the importance of multiple (charge-exchange) scattering. The combined use of the exclusive and inclusive cross sections is discussed.NUCLEAR REACTIONS $^{6,7}\mathrm{Li}$(${\ensuremath{\pi}}^{+}$,$p$)$^{5,6}\mathrm{Li}$, ${T}_{\ensuremath{\pi}}=75$ MeV, $\ensuremath{\theta}=20\ensuremath{-}116\ifmmode^\circ\else\textdegree\fi{}$, ${T}_{\ensuremath{\pi}}=175$ MeV, ${\ensuremath{\theta}}_{p}=20\ensuremath{-}95\ifmmode^\circ\else\textdegree\fi{}$ measured $\ensuremath{\sigma}(\ensuremath{\theta})$; $^{6}\mathrm{Li}$(${\ensuremath{\pi}}^{\ifmmode\pm\else\textpm\fi{}}$,$p$), ${T}_{\ensuremath{\pi}}=75, 175$ MeV, ${\ensuremath{\theta}}_{p}=20\ifmmode^\circ\else\textdegree\fi{}$ measured $\ensuremath{\sigma}({T}_{p})$; discussed reaction mechanism effects.

Elastic scattering of 180-MeV ..pi../sup +/ and ..pi../sup -/ on /sup 3/He and tritium has been measured from theta/sub ..pi../(c.m.) = 44/sup 0/ to 96/sup 0/. The superratio Requivalent(dsigma(..pi../sup +/+/sup 3/H)/dsigma(..pi../sup -/+/sup 3/He))/(dsigma(..pi../sup +/+/sup 3/He) dsigma(..pi../sup -/+/sup 3/H)) is found to vary with angle reaching a maximum of 1.31 +- 0.09 at theta/sub ..pi../ = 65/sup 0/. The direct Coulomb effects do not account for the observed differences of R from 1.0 which is the expected value on the basis of charge symmetry.

Data for elastic scattering of ..pi../sup +/ and ..pi../sup -/ from /sup 13/C at T/sub ..pi../ = 162 MeV between theta/sub lab/ = 22/sup 0/ and 105/sup 0/ were analyzed by an optical model. Good fits were obtained with neutron and proton ground state densities of three-parameter Fermi shape having the same rms radius. Inelastic data for the quadrupole transitions to the (3/2)/sup -/ (3.68 MeV) and (5/2)/sup -/ (7.55 MeV) states and the octupole transition to a proposed (5/2)/sup +/, (7/2)/sup +/ doublet (11.82 MeV) were analyzed using a collective model. The extracted strengths for the neutron and proton parts of the transitions are compared to the results of electron scattering and ..gamma..-ray studies.

Inelastic scattering of 163 MeV ..pi../sup -/ and ..pi../sup +/ to the collective states of /sup 90/Zr and /sup 118/Sn was used to determine the neutron-proton composition of the transitions. The lowest 2/sup +/ and 3/sup -/ states were examined for both targets, as were the low-energy octupole, giant quadrupole, and giant monopole excitations. Only slight deviations from the features expected for a hydrodynamic model are observed for the low-lying 3/sup -/ and 2/sup +/ states of /sup 118/Sn, but these states are observed to be proton-like in /sup 90/Zr. The giant quadrupole resonances and giant monopole resonances in both targets show a significantly greater ..pi../sup -/ than ..pi../sup +/ strength, while the low-energy octupole resonance is excited symmetrically.

Differential cross sections have been measured at θ ≈20–120° at 50, 100 and 200 MeV. Salient features of the angular distributions are Coulomb interference effects at 50 MeV and clear spin-flip contributions to π − compared to π + scattering in the angular region of θ ≈80° dominated by the πN p-wave minimum. Comparison with optical model calculations account for the data up to 200 MeV while this first-order scattering theory misses conspicuous features of data at 295 MeV.

Measurements are reported for the elastic and inelastic scattering of 800 MeV protons from $^{40}\mathrm{Ca}$. Differential cross sections were measured out to 42\ifmmode^\circ\else\textdegree\fi{} while analyzing powers were obtained out to 30\ifmmode^\circ\else\textdegree\fi{}. The angular distributions are diffractive in character at all angles. Theoretical analysis of the data was carried out in the framework of the diffraction multiple scattering theory. The following results were obtained: (i) Diffraction multiple scattering theory reproduces the data qualitatively out to the large momentum transfers. (ii) For the ground state density distribution ${〈{{r}_{p}}^{2}〉}^{\frac{1}{2}}\ensuremath{-}{〈{{r}_{n}}^{2}〉}^{\frac{1}{2}}=0.142\ifmmode\pm\else\textpm\fi{}0.075$ fm is obtained and the analysis favors the value of the correlation length ${\ensuremath{\xi}}_{c}=\ensuremath{-}0.5$ fm. (iii) The excitation of the lowest-lying collective states (${3}^{\ensuremath{-}}$, ${5}^{\ensuremath{-}}$, ${2}^{+}$) was analyzed using one-phonon excitation macroscopic parameters. The values of the ${\ensuremath{\beta}}_{2}$, ${\ensuremath{\beta}}_{3}$, ${\ensuremath{\beta}}_{5}$ parameters obtained agree quantitatively with lower energy ($p$,${p}^{\ensuremath{'}}$) scattering results.

Inelastic scattering of 180 MeV {pi}{sup {minus}} and {pi}{sup +} from {sup 58,60,62,64}Ni shows a prominent quadrupole feature near 65{ital A}{sup {minus}1/3} MeV, identified as the familiar isoscalar giant quadrupole resonance. For the heavier two isotopes, the {pi}{sup {minus}} scattering cross sections greatly exceed those for {pi}{sup +}, the same effect previously noted in pion scattering on heavy nuclei. Since these four nickel targets contain a range of single-nucleon binding energies, these new data demonstrate the influence of these single-particle effects on the apparent isospin response, increasingly neutronlike for the heavier isotopes.

A comparison of differential cross sections for inelastic scattering of 130 MeV positive and negative pions has been made for studying the giant resonance region in $^{118}\mathrm{Sn}$ and $^{40}\mathrm{Ca}$. In addition, several of the low-lying collective states in each target were examined. Comparison to distorted wave impulse approximation calculations allowed collective deformation lengths \ensuremath{\beta}R and fractions of the energy-weighted sum rules to be extracted. For bound collective states, the strengths for ${\ensuremath{\pi}}^{+}$ and ${\ensuremath{\pi}}^{\mathrm{\ensuremath{-}}}$ were nearly equal, as has been found for other scattering probes. Giant quadrupole and dipole excitations in $^{40}\mathrm{Ca}$ (T=0) had nearly equal ${\ensuremath{\pi}}^{+}$ and ${\ensuremath{\pi}}^{\mathrm{\ensuremath{-}}}$ sum rule strengths. Quadrupole and monopole excitations in $^{118}\mathrm{Sn}$ near 14 MeV show about twice the ${\ensuremath{\pi}}^{\mathrm{\ensuremath{-}}}$ transition strengths compared to those for ${\ensuremath{\pi}}^{+}$, contrary to expectations from simple isoscalar models.

The results for ..pi../sup + -/ + /sup 9/Be elastic scattering at E/sub lab/ = 162 MeV are shown to provide evidence for quadrupole contributions to the elastic scattering of pions. The strong-coupling rotational model is used to relate the measured inelastic scattering cross sections to the elastic scattering cross sections.

The (..pi../sup +/, p) reaction has been studied at T/sub ..pi../ = 90 and 180 MeV on /sup 12/C, and at T/sub ..pi../ = 90 and 170 MeV on /sup 13/C. The resolution was sufficient to resolve many single levels in the residual nuclei, and angular distributions were obtained between laboratory angles of 10/sup 0/ and 115/sup 0/. A comparison between the present (..pi.., p) data and existing high-energy (p,d) data in terms of a model assuming intermediate pion exchange in the (p,d) reaction indicates that the (..pi..,p) reaction is an important subprocess in the (p,d) reaction. The present data also suggest that pion rescattering is likely to be a fundamental part of the (..pi.., p) reaction mechanism.

Differential cross sections for inelastic pion scattering from $^{12}\mathrm{C}$ at incident energies of 100 to 291 MeV and momentum transfers \ensuremath{\le}300 MeV/c have been measured and are compared to results obtained from other probes, particularly electrons and protons. Angular distributions and excitation functions are presented for many of the bound states, including the 4.44-MeV (${2}^{+}$,0), 7.66-MeV (${0}^{+}$,0), 9.64-MeV (${3}^{\mathrm{\ensuremath{-}}}$,0), 12.71-MeV/15.11-Mev (${1}^{+}$;0,1) doublet, 16.11-MeV (${2}^{+}$,1), 19-MeV (${4}^{\mathrm{\ensuremath{-}}}$;0,1) doublet, and ${2}^{\mathrm{\ensuremath{-}}}$ states at 18.25 and 19.4 MeV. Distorted-wave impulse-approximation calculations using both macroscopic and microscopic descriptions of the nuclear wave functions are compared to the data. The observation of an anomalous excitation function for the 15.11-MeV level and the observation of dramatic ${\ensuremath{\pi}}^{+}$/${\ensuremath{\pi}}^{\mathrm{\ensuremath{-}}}$ asymmetries near 18 and 19 MeV excitation due to isospin mixing between ${2}^{\mathrm{\ensuremath{-}}}$ states and between members of the ${4}^{\mathrm{\ensuremath{-}}}$ doublet are of particular interest.

The inelastic scattering of 162-MeV pions by $^{14}\mathrm{N}$ has been studied over the angular range 35\ifmmode^\circ\else\textdegree\fi{} to 115\ifmmode^\circ\else\textdegree\fi{} in the laboratory system. The data were analyzed with a model which incorporates shell model wave functions into a distorted wave impulse approximation. Reduced transition probabilities obtained for a number of low-lying states are compared to previous data to validate the model. Among new assignments and shell model descriptions presented for several higher excited states is an assignment for the yrast ${5}^{\ensuremath{-}}$ state.

Proton spectra of /sup 3,4/He(..pi../sup + -/,p) and /sup 27/Al(..pi../sup + -/,p) have been measured at theta/sub p/ = 20/sup 0/ for T/sub ..pi../ = 50, 100, 150, 200, and 250 MeV, and at theta/sub p/ = 20/sup 0/ and 40/sup 0/ for T/sub ..pi../ = 295 MeV. A small contributor to these spectra is the exclusive pion absorption reaction for which the cross section of /sup 4/He(..pi../sup +/,p)/sup 3/He is reported. Major contributions are identified to come from quasifree ..pi..N..--> pi..p scattering and ..pi..NN..-->..Np absorption for which cross sections are also reported. The quasifree cross sections are compared with those of the free reactions ..pi..N..--> pi..p and ..pi..d..-->..pp. We use these results to assess the contribution of quasifree reactions to the total reaction cross section. The comparison of the quasifree ..pi..NN..-->..Np reaction relative to ..pi..d..-->..pp is discussed in terms of differences in the attenuation and the dynamics of the reactions. This information is of interest for the phenomenological interpretation of complex reactions such as the two-nucleon absorption model of /sup 3/He(..pi../sup -/, n)/sup 2/H, /sup 4/He(..pi../sup -/, n)/sup 3/H, and /sup 4/He(..pi../sup +/, p)/sup 3/He in which ..pi..d..-->..pp is assumed to be an elementary process. This experiment also providesmore » information on the cross section of ..pi../sup -/pp..-->..pn from which we determine the dependence of pion absorption on the isospin of the initial NN state.« less

Angular distributions for the elastic and inelastic scattering of 291-MeV ${\ensuremath{\pi}}^{+}$ and ${\ensuremath{\pi}}^{\ensuremath{-}}$ by $^{9}\mathrm{Be}$, Si, $^{58}\mathrm{Ni}$, and $^{208}\mathrm{Pb}$ have been measured. The characteristics of two first-order optical potentials have been investigated, and reasonable agreement with the elastic scattering data has been obtained. Macroscopic distorted-wave impulse approximation calculations of the inelastic scattering with Kisslinger potentials are reasonably successful in reproducing the experimental data. The inelastic scattering results for $^{9}\mathrm{Be}$ provide evidence for the importance of radial localization effects in pion inelastic scattering.NUCLEAR REACTIONS $^{9}\mathrm{Be}(\ensuremath{\pi},{\ensuremath{\pi}}^{\ensuremath{'}})$, $\mathrm{Si}(\ensuremath{\pi},{\ensuremath{\pi}}^{\ensuremath{'}})$, $^{58}\mathrm{Ni}(\ensuremath{\pi},{\ensuremath{\pi}}^{\ensuremath{'}})$, $^{208}\mathrm{Pb}(\ensuremath{\pi},{\ensuremath{\pi}}^{\ensuremath{'}})$, ${E}_{\ensuremath{\pi}}=291$ MeV, measured $\frac{d\ensuremath{\sigma}}{d\ensuremath{\Omega}}$; optical potential and DWIA collective analyses.

The inelastic scattering of 162 MeV ..pi../sup +/ and ..pi../sup -/ to 8/sup -/ states in /sup 54/Fe was studied. Isoscalar and isovector structure amplitudes were extracted for each state. The summed isoscalar strength corresponds to only 11% of that predicted in an ((f/sub 7/2/)/sup -3/ g/sub 9/2/)/sub 8/- calculation, while 38% of the isovector strength is observed. This is similar to the quenching of strength observed in lighter nuclei and demonstrates that the strong quenching of the isoscalar spin-flip strength persists in the f-p shell.

New, large-momentum-transfer 0.8 GeV p+/sup 208/Pb elastic analyzing power data are presented and compared to optical model predictions using the Kerman-McManus-Thaler microscopic optical potential. This comparison provides an important test of multiple scattering theories since the predictions are quite sensitive to the assumed nucleon-nucleon scattering amplitudes and are not sensitive to the details of the nuclear densities. We show that improvement in the agreement between experiment and a parameter-free theoretical prediction is obtained when the calculation includes the electromagnetic spin-orbit potential which arises from the coupling of the projectile proton's magnetic moment and the Coulomb field of the target nucleus. The sensitivity of the predicted analyzing power to the various ingredients of the theory is also investigated, and the importance of the inclusion of target-nucleon correlations (in the second-order Kerman-McManus-Thaler potential) for proper explanation of the data is discussed.

Cross sections for the /sup 7/Li( p,d)/sup 6/Li and /sup 13/C( p,d)/sup 12/C reactions have been measured at a bombarding energy of 800 MeV. Exact finite range distorted-wave Born-approximation calculations are compared to cross sections for known levels excited by 1p neutron pickup and are found to give reasonable agreement in most cases. However, the large strength for the excitation of the 2.184 MeV /sup 6/Li 3/sup +/ level is not reproduced by the calculation. Levels in /sup 12/C are strongly excited at 800 MeV which are not appreciably populated in lower energy ( p,d) studies.