The cross sections for the production of charged pions and protons from the annihilation of 608-MeV/c antiprotons on $^{12}\mathrm{C}$, $^{89}\mathrm{Y}$, and $^{238}\mathrm{U}$ are presented. The sources of pion and proton emission are inferred from the rapidity distributions of the data. The results are compared to and seen to be in good agreement with intranuclear-cascade calculations.

Recent results from LEAR experiment PS187 are presented. Preliminary data for the inclusive production of π+, K+, and p from the annihilation of 180 MeV antiprotons in 28Si and 238U are compared with predictions of intranuclear cascade calculations. Proton and pion production data are well reproduced by the calculations, but kaon yields at low momenta appear to be strongly suppressed in the experimental data.

A magnetic spectrometer with an angular acceptance of 360° and a solid angle of 0.5 sr is described. It can detect and identify light charged particles in the momentum range 0.1 GeV/c < p < 1.2 GeV/c, with a momentum resolution of 1 to 10%. It can be configured to allow inclusive single particle as well as correlated multiparticle (⪅ 10) measurements. The performance of the spectrometer is discussed in light of p + A → π ± + X and p + A → π ±, K ±, p, p, d + X experiments conducted at LAMPF, TRIUMF and LEAR (CERN).

We discuss the effect of antiproton annihilation within nuclei from the perspective of realistic intranuclear cascade calculations (INC). The results indicate a significant energy deposition for a class of annihilations that are shown to occur relatively deep within the nucleus. In addition, promising experimental observables and triggers are identified. The calculations are especially relevant to LEAR antiproton-nucleus experiments, particularly PS 187. This experiment is described here and possible future investigations are suggested.

The real part V(r); E) of the nucleon-nucleus mean field is assumed to have a Woods-Saxon shape, and accordingly to be fully specified by three quantities: the potential depth Uv(E), radius RV(E) and diffuseness av(E). At a given nucleon energy E these parameters can be determined from three different radial moments [rq]v = (4π/A) ∝V(r; E)rq dr. This is useful because a dispersion relation approach has recently been developed for extrapolating [rq]V(E) from positive to negative energy, using as inputs the radial moments of the real and imaginary parts of empirical optical-model potentials V(r; E) + iW(r; E). In the present work, the values of Uv(E), Rv(E) and av(E) are calculated in the case of neutrons in 208Pb in the energy domain −20 < E < 40 MeV from the values of [rq]V(E) for q = 0.8, 2 and 4. It is found that both UV(E) and Rv(E) have a characteristic energy dependence. The energy dependence of the diffuseness aa(E) is less reliably predicted by the method. The radius RV(E) increases when E decreases from 40 to 5 MeV. This behaviour is in agreement with empirical evidence. In the energy domain −10 MeV < E < 0, RV(E) is predicted to decrease with decreasing energy. The energy dependence of the root mean square radius is similar to that of RV(E). The potential depth Uv slightly increases when E decreases from 40 to 15 MeV and slightly decreases between 10 and 5 MeV; it is consequently approximately constant in the energy domain 5 < E < 20 MeV, in keeping with empirical evidence. The depth Uv increases linearly with decreasing E in the domain −10 MeV < E < 0. These features are shown to persist when one modifies the detailed input of the calculation, namely the empirical values of [rq]v(E) for E > 0 and the parametrization [rq]w(E) of the energy dependence of the radial moments of the imaginary part of the empirical optical-model potentials. In the energy domain −10 MeV < E < 0, the calculated V(r; E) yields good agreement with the experimental single-particle energies; the model thus accurately predicts the shell-model potential (E < 0) from the extrapolation of the optical-model potential (E > 0). In the dispersion relation approach, the real part V(r; E) is the sum of a Hartree-Fock type contribution VHF(r; E) and of a dispersive contribution ΔV(r; E). The latter is due to the excitation of the 208Pb core. The dispersion relation approach enables the calculation of the radial moment [rq]ΔV(E) from the parametrization [rq]w(E): several schematic models are considered which yield algebraic expressions for [rq]ΔV(E). The radial moments [rq]HF(E) are approximated by linear functions of E. When in addition, it is assumed that VHF(r; E) has a Woods-Saxon radial shape, the energy dependence of its potential parameters (UHF, RHF, aHF) can be calculated. Furthermore, the values of ΔV(r; E) can then be derived. It turns out that ΔV(r; E) is peaked at the nuclear surface near the Fermi energy and acquires a Woods-Saxon type shape when the energy increases, in keeping with previous qualitative estimates. It is responsible for the peculiar energy dependence of RV(E) in the vicinity of the Fermi energy.

An inexpensive threshold Cherenkov detector that has proven useful in distinguishing pions (130 ⩽ Tπ ⩽ 770 MeV) from other particles produced in intermediate energy nuclear collisions is described. The detector is constructed by laminating a thin sheet of Pilot 425 scintillator to UVT acrylic. The highly directional Cherenkov radiation absorbed by the Pilot 425 is isotropically reemitted, yielding useful Cherenkov signals for particles incident over a broad angular range (±45°).

We have measured $\ensuremath{\alpha}$ + $^{12}\mathrm{C}$ total reaction cross sections (${\ensuremath{\sigma}}_{R}$) at ${E}_{\mathrm{lab}}=94 \mathrm{and} 173$ MeV/N using the attenuation method. Our data indicate a decreasing ${\ensuremath{\sigma}}_{R}(E)$ at intermediate incident energies. These results, along with existing measurements, are in quantitative agreement with theoretical predictions for ${\ensuremath{\sigma}}_{R}(E)$ which are based on nucleon-nucleon total cross sections.NUCLEAR REACTIONS Attenuation measurements of $\ensuremath{\alpha}$ + $^{12}\mathrm{C}$ total reaction cross sections at ${E}_{\mathrm{lab}}=94 \mathrm{and} 173$ MeV/N.

A geometrical model for Pauli blocking and Fermi motion effects in ion-ion collisions is presented. The results, given as effective nucleon-nucleon total cross sections, incicate that the Pauli blocking reduces the nucleon-nucleon cross section in the ion-ion environment by a larger amount than previously estimated.

A new technique has been developed, employing a localized perturbation of the radial nuclear optical potential, which permits direct investigation of the sensitivities of optical model analysis of elastic scattering data to the details of the radial potential. It is found that both light- and heavy-ion scattering probe primarily the nuclear surface region. Higher energy scattering data probe further into the interior than lower energy data. The value of the potential at the center of the nucleus cannot be determined, but only inferred if a fixed parametrization such as Woods-Saxon geometry is specified. In addition, it is found that the region of radial sensitivity of the imaginary potential is systematically closer to the center of the nucleus than is that of the real potential.NUCLEAR REACTIONS Radial sensitivity of optical model calculations to elastic $\ensuremath{\sigma}(\ensuremath{\theta})$ data analyzed for $p$+$^{12}\mathrm{C}$, $\ensuremath{\alpha}$+$^{58}\mathrm{Ni}$, $^{16}\mathrm{O}$+$^{28}\mathrm{Si}$ at low and intermediate incident energies.

We have employed the line shape analysis technique to study nuclear spin alignment produced in the $^{12}\mathrm{C}$ + $^{16}\mathrm{O}$ reaction populating the ${2}^{+}$ 4.43-MeV state in $^{12}\mathrm{C}$. We present excitation functions of $m$-substate population $P(m)$ measured in the range ${E}_{\mathrm{c}.\mathrm{m}.}=19\ensuremath{-}22.6$ MeV and detailed angular distributions of $P(m)$ obtained at ${E}_{\mathrm{c}.\mathrm{m}.}=21.7,21.9, \mathrm{and} 22.3$ MeV. Results have been analyzed in terms of a single resonance with sharp spin in the compound nucleus and found to contradict previous spin assignment based on studies of angular distributions of cross section in the ${E}_{\mathrm{c}.\mathrm{m}.}\ensuremath{\approx}22 \mathrm{to} 22.6$ MeV region.NUCLEAR REACTIONS $^{12}\mathrm{C}$($^{16}\mathrm{O}$, $^{12}\mathrm{C}^{*}$)$^{16}\mathrm{O}$, ${E}_{\mathrm{lab}}=45\ensuremath{-}53$ MeV. Measured $\ensuremath{\sigma}(E;E^{12}\mathrm{C}^{*},\ensuremath{\theta})$, deduced $^{12}\mathrm{C}^{*}$ (4.43 MeV, ${2}^{+}$) spin alignment ($\ensuremath{\sigma}(E;m,\ensuremath{\theta})$). $^{16}\mathrm{O}$ + $^{12}\mathrm{C}$ resonances, deduced $J$, $\ensuremath{\pi}$.

Microscopic calculations of the total reaction cross sections for protons on $^{12}\mathrm{C}$, $^{27}\mathrm{Al}$, $^{40}\mathrm{Ca}$, and $^{208}\mathrm{Pb}$, and neutrons on $^{27}\mathrm{Al}$ and $^{208}\mathrm{Pb}$ have been made, which provide for the first time an excellent description of the data for projectile energies from 15 MeV through 1 GeV. The calculations are based on the experimental nucleon-nucleon total cross sections and explicitly include the effects of the real nuclear potential, the Coulomb potential, Pauli blocking, and Fermi motion.

An experimental study of the $^{20}\mathrm{Ne}$ + $^{12}\mathrm{C}$ systems reveals a large cross section for inelastic scattering with large negative $Q$ values at backward angles. The differential cross section is proportional to $\frac{1}{{sin\ensuremath{\theta}}_{\mathrm{c}.\mathrm{m}.}}>100\ifmmode^\circ\else\textdegree\fi{}$ and has characteristics consistent with the decay of an orbiting $^{20}\mathrm{Ne}$ + $^{12}\mathrm{C}$ dinuclear system.

We have measured elastic scattering of 131.5 MeV 12C by 28 Si. These data are compared with measurements at 60, 74 and 186 MeV, and with optical-model analyses for these and lower energies. We find that there exists no evidence for energy dependence in the best-fit optical potentials for 12C energies of 131.5 and 186 MeV, but the potentials required for energies between 30 and 74 MeV are highly energy dependent.

Angular distributions at angles $130\ifmmode^\circ\else\textdegree\fi{}<{\ensuremath{\theta}}_{\mathrm{cm}}<180\ifmmode^\circ\else\textdegree\fi{}$ have been measured for $^{12}\mathrm{C}$ + $^{28}\mathrm{Si}$, $^{32}\mathrm{S}$, $^{40}\mathrm{Ca}$ as well as $^{9}\mathrm{Be}$, $^{13}\mathrm{C}$ + $^{28}\mathrm{Si}$ in the energy range $20 \mathrm{MeV}<{E}_{\mathrm{cm}}<35 \mathrm{MeV}$. Cross sections rising towards 180\ifmmode^\circ\else\textdegree\fi{} are observed for all reactions. Excitation functions for the back angle enhancement show distinct structures, most pronounced for $^{12}\mathrm{C}$ + $^{28}\mathrm{Si}$. Angular distributions for $^{12}\mathrm{C}$, especially those corresponding to peaks in the excitation function show oscillations of the type ${P}_{J}^{2}(cos\ensuremath{\theta})$. The $^{12}\mathrm{C}$ back angle enhancement decreases with target mass. Backscattering of the non-$\ensuremath{\alpha}$ nuclei $^{9}\mathrm{Be}$ and $^{13}\mathrm{C}$ is reduced by about two orders of magnitude in comparison with $^{12}\mathrm{C}$. Standard theoretical approaches fail to explain all the observed effects.NUCLEAR REACTIONS $^{12}\mathrm{C}$ + $^{28}\mathrm{Si}$, $^{12}\mathrm{C}$ + $^{32}\mathrm{S}$, $^{12}\mathrm{C}$ + $^{40}\mathrm{Ca}$, $^{9}\mathrm{Be}$ + $^{28}\mathrm{Si}$, $^{13}\mathrm{C}$ + $^{28}\mathrm{Si}$, measured $\ensuremath{\sigma}(\ensuremath{\theta},E)$ elastic scattering, $130\ifmmode^\circ\else\textdegree\fi{}<{\ensuremath{\theta}}_{\mathrm{c}.\mathrm{m}.}<180\ifmmode^\circ\else\textdegree\fi{}$, $20 \mathrm{MeV}<{E}_{\mathrm{c}.\mathrm{m}.}<35 \mathrm{MeV}$, deduced ${J}^{\ensuremath{\pi}}$ of resonances.