The interaction between positive pions and deuterons at 47.5 MeV

The interaction of 47.5 (±0.5) MeV positive pions with douterons was studied using a scintillation counter telescope as the pion spectrograph. With an energy resolution sufficient to separate the elastic from inelastically scattered pions, the system was used to measure the cross sections for these reactions as well as the non-radiative pion capture process over the angular range of 22.5°–157.5°. The scattering results are well-fitted by recent theoretical calculations provided appropriate pion-nucleon phase shifts are used. The protons from the non-radiative capture reaction are fitted by a differential cross section of the form: $\text{d}\text{σ/}\text{d}\text{Ω ∝ A +}\text{cos}{}^2\text{θ}$, with A = 0.31 ± 0.03.     

Elastic scattering of positive pions from 12C at 30, 40 and 50 MeV

We have measured the angular distribution of π⁺ elastically scattered from ${}^{12}\text{C at}\text{E}\text{?}{}_{\mathrm{\pi }}\text{= 28.4, 38.6}\text{and}\text{48.9}\text{MeV}$. The angular range was between 13° and 165° lab. Scattered pions were detected with two counter telescopes which required pion identification through the observation of the decay muon. Data agree well with calculations derived from the free πn scattering amplitudes when absorption effects have been included.     

Elastic scattering of positive pions by O between 80 and 340 MeV

Angular distributions of cross sections for π⁺ elastic scattering by ¹⁶O have been measured between 14° and 138° at five energies (79, 114, 163, 240 and 343 MeV). They are compared to calculations using a first-order static model and an isobar doorway model. Phase-shift analyses have been done using the theoretical inputs as guidelines. The validity of these models is discussed.     

Scattering of negative pions on helium

Differential cross sections for negative pion scattering on ⁴He have been measured at five pion kinetic energies between 110 and 260 MeV in the angular range from 5° to 180°. Total cross sections have also been measured at eleven energies between 67 and 285 MeV. The differential cross sections have been fitted with a phenomenological expression for the nuclear scattering amplitude. Conventional phase shifts have been reconstructed starting from the parameters of the fits.     

Photoproduction of pions at low energy

Presented in this paper is a field theory model for photoproduction of pions at low energy. In particular, it is shown that certain interaction terms, which were previously considered to be essential in order to explain the experimental situation corresponding to the spin-3/2 resonances, are really unnecessary and that the presence of these terms are not justifiable from the theoretical point of view. Further, the free parameters in the theory representing the off-mass-shell effects of the spin-3/2 particles are fixed on the basis of theoretical considerations.     

Low-energy elastic scattemng of pions by the deuteron

The problem of the elastic scattering of pions by a deuteron is considered using the separable representation of the two-body t-matrix. The Faddeev equations are reduced to a set of one-dimensional integral equations by separating the angular variables. The dependence of the π-d scattering length on the form of two-body interaction and on the values of the π-N scattering lengths is studied in the case of a one-term nonlocal potential with separable variables. The π-d scattering length proves to be practically independent of the two-body interaction form, and is essentially dependent on the values of the π-N scattering lengths.     

Branching ratios for stopped pions in deuterium

The ratios $\text{S =}\text{ω(π}{}^{\mathrm{?}}\text{d}\text{→}\text{nn}\text{)}\text{ω(π}{}^{\mathrm{?}}\text{d}\text{→}\text{nn}\text{γ)}$ has been measured for negative pions stopping in deuterium gas at pressures up to 100 atm. The result is S = 2.83 ± 0.04 which is a factor of two more accurate than previous measurements.     

Photoproduction of neutral pions on hydrogen below 500 MeV

At the Bonn 500 MeV electron synchrotron differential cross sections of the reactionγ+p→Π ⁰+p were measured in the kinematical region of photon energies between 340 and 420 MeV and pionCM angles from 10° to 70° by means of detecting the two photons from the pion decay by two Cherenkov counters.     

Photoproduction of neutral pions on hydrogen at photon energies between 200 and 440 MeV

At the Bonn 500 MeV electron synchrotron the differential cross section of the reaction γ+p → π⁰+p has been measured detecting the recoil proton by a magnetic spectrometer. Angular distributions between pion c.m. angles of 50 ° and 160 ° were taken at photon energies between 220 and 420 MeV.     

Energy spectra of neutrons emitted following the absorption of stopped negative pions in light nuclei

Energy spectra of neutrons emitted following the absorption of stopped negative pions in carbon, nitrogen and oxygen were measured from about 2.5 MeV up to the kinematical limit. The experiments were carried out at the biomedical pion channel πE3 of the Swiss Institute for Nuclear Research (SIN). The evaporation part of the spectra was extrapolated to zero energy using the formula of Le Couteur. Various parameters like mean neutron energies and neutron multiplicities are given. The data are compared with experimental data obtained by other authors and with results of intranuclear cascade calculations.     

Spectroscopy of low-lying positive parity states in 30P from the study of the reaction (3He,d) at 14.0 MeV

The reaction ²⁹Si(³He, d)³⁰P was studied at an incident energy of 14.0 MeV. Spectroscopic strengths for 14 positive parity states up to an excitation of 4.50 MeV have been obtained using DWBA analysis. The incident channel optical-model parameters for the DWBA calculations were extracted from elastic scattering cross sections measured also at 14.0 MeV.     

Photoproduction of pions from deuterons in impulse approximation

The differential cross section for photoproduction of pions from deuterons is calculated in the relativistic impulse approximation. In the discussion of the resulting formula special emphasis is given to the following three problems: test of the impulse approximation, test of the photoproduction amplitudes, and measurement of the deuteron wave-function.     

Photoproduction of ω-Mesons at ELSA and the role of azimuthal asymmetries

Measurements of ω photoproduction of the Crystal-Barrel/TAPS experiment at the ELSA accelerator of Bonn University are presented which used linearly polarized tagged photon beam from threshold to Eγ = 1700MeV. The azimuthal asymmetries ∑and ∑πindicate s-channel resonance contributions on top of the established t-channel exchange processes. These findings are further enhanced by a very first measurement of the G-asymmetry which, in addition to the polarized photon beam, also requires a longitudinally polarized proton target. An intuitive interpretation of the specific sensitivity of the azimuthal asymmetries to the reaction mechanisms involved is given.     

Elastic photoproduction of charged pions on He and H in the Δ(1232) resonance region

Photoproduction of charged pions on ³He and ³H has been measured in the Δ(1232)-resonance region. Differential cross sections are presented as functions of the photon energy at fixed momentum transfer and compared to experimental data and theoretical calculations.     

Measurements of the total neutron cross sections of hydrogen and carbon at 0.5, 1.0 and 2.0 MeV

The total neutron cross sections of carbon and hydrogen were measured at 0.5, 1.0 and 2.0 MeV. The determination of the H(n, n) cross section often used as a standard was the major objective of the present measurements and values were obtained with accuracies of ～0.2 %, 0.2 % and 0.4 % respectively. A parameter set for the shape-independent effective-range approximation of the H(n, n) cross section was obtained with the present and other recent data indicating lower crosssection values than given in the Hopkins-Breit analysis.     

Photoproduction of neutral pions off hydrogen at photonenergies between 0.55 and 2.2 GeV at a cm-angle of 120°

The differential cross section has been measured for the reaction γ+p→π^o + p at the Bonn 2.5 GeV electron synchrotron in the energy range from 0.55 to 2.2 GeV at a c.m.angle of 120 degrees.     

Rotational excitations in residual nuclei produced by stopped negative pions on targets of Ho, Lu, Lu, Hf, and Ta

Reactions produced by stopped negative pions on targets of ¹⁶⁵Ho, ¹⁷⁵Lu, ¹⁷⁶Lu, ¹⁷⁹Hf, and ¹⁸¹Ta are investigated by measuring photons coincident with the stopped pions. These photons were detected with an 80 cm³ Ge(Li) detector and identified as pionic X-rays or rotational γ-rays from the residual nuclei. Pion capture is found to result in the excitation of high-spin states. Yields for the residual nuclei are inferred from the observed γ-transitions and compared to calculations based on the exciton model for pre-equilibrium emission followed by particle evaporation. Preliminary results of a pion stop, γn coincidence experiment are presented and compared to the calculations.     

Inelastic electron scattering at 180° from 14C

Inelastic scattering of 37, 50, and 60 MeV electrons at 180° from ¹⁴C has been studied. Cross sections for the excitation of eight states in ¹⁴C with excitation energy less than 16 MeV have been observed. Most of the strength is observed to be concentrated in one transition at 11.31 MeV which is assigned a spin and parity of 1⁺. The total width of this state is observed to be 207 ± 13 keV, while the electromagnetic transition width is determined to be 6.8 ± 1.4 eV.