B. Mecking

Measurement of total photonuclear cross sections in the Δ-resonance region☆

Abstract Double differential cross sections for the photo-emission of photons and charged pion production were investigated for a number of target nuclei (He, Be, C, O, Ai, Ti, Cu, Sn, Pb) in the photon energy range k = (215−386) MeV. On the basis of these experimental results the total hadronic cross section was determined.

Experimental investigation of deuteron photodisintegration in the δ-resonance region

Abstract Differential cross sections for the deuteron photodisintegration process were measured for photon energies between 200 and 440 MeV using the tagged photon beam facility of the Bonn 500 MeV synchrotron. At eight angles between 18° and 145° charged particles were detected simultaneously in time-of-flight spectrometers consisting of scintillation counters. Above the resonance region the measured cross sections agree fairly well with earlier results, whereas there are larger discrepancies at low photon energies.

Measurement of the total cross section for 235U and 238U photofission in the δ-resonance region

Abstract The total cross section for the photoemission of fission fragments σ(γ, F) has been measured for 235U and 238U using tagged bremsstrahlung photons in the energy range 120–460 MeV. The fission fragments were detected in parallel plate avalanche detectors. The results are compared with other information on the photonuclear absorption cross section.

Experimental investigation of the reaction12C(γ, π0)X in the photon energy range between threshold and 450 MeV

The photoproduction of neutral pions on12C has been investigated between threshold and 450 MeV photon energy using the tagged photon beam at the Bonn 500 MeV synchrotron and a large acceptance detector. Theπ0 detector consists of cylindrical wire chambers covering a solid angle of nearly 4π. Using a scintillation counter as an active12C target an attempt was made to separate coherent and incoherentπ0 photoproduction. The measured total and differential cross sections are compared to corresponding theoretical calculations.

Inclusive charged pion photoproduction on12C using tagged photons in the energy range (200–390) MeV

The photoproduction of charged pions on12C has been investigated using the tagged photon beam facility at the Bonn 500 MeV synchrotron. Pions were detected in a broad range magnetic spectrometer. Double differential cross sections for pion emission at fixed photon energies are presented. The integration of the measured distributions yields the total cross section for inclusive pion production. The data are compared to the predictions of a simple model that takes the quasifree production of pions and their subsequent scattering and reabsorption into account.

Measurement of total cross sections for π0 photoproduction on nuclei in the Δ-resonance region☆

Abstract Total cross sections for π 0 photoproduction on Be, C, Al, Cu, Sn and Pb have been measured in the photon energy range k = 220–450 MeV using the tagged photon beam of the Bonn 500 MeV synchrotron. The data show a broad maximum around k = 350 MeV. The A -dependence can be described by σ A ∝ A 0.66 . The results are compared to charged pion production and to total hadronic cross sections.

Experimental study of the photoemission of protons off12C using tagged photons in the energy range 200–385 MeV

Data are presented for proton emission off12C using tagged photons in the energy range 200–385 MeV. The protons are detected in a magnetic spectrometer. In addition, charged or neutral particles can be measured with a scintillation counter setup. Contributions to the proton energy spectra from primary pion production and quasideuteron reactions are separated using the coincidence data. The total12C(γ, p)X cross section is derived as a function of the photon energy. The data are compared to the predictions of an intranuclear cascade calculation. Final state interactions have to be taken into account to describe the data.

Experimental investigation of the 4He(γ, p)3H reaction in the Δ -resonance region

Abstract The 4 He(γ, p) 3 H reaction was investigated in the photon energy region between 200 and 450 MeV and at proton c.m. angles between 30° and 150°. The outgoing particles were detected in coincidence in two time-ot-flight spectrometers consisting of scintillation counters; energies and angles of both particles were determined. The measured angular distributions show a strong forward peak. The differential cross sections and the total cross section fall off smoothly with increasing photon energy. However, the slope is not as steep as in the low energy region.

The tagged photon beam facility at the Bonn 500 MeV synchrotron

Abstract A facility for the investigation of medium energy photonuclear reactions is described. A bremsstrahlung tagging system produces a precisely known flux of monochromatic photons in the energy range between 100 and 450 MeV. Resolution and intensity of the system are given. Photoemitted particles can be detected in various large solid angle detectors. The performance of the facility and future developments are discussed.

Photon-induced emission of pions and protons from various nuclei in the Δ-resonance region☆

Abstract Double differential cross sections for the photon induced emission of π − , π + and protons from Be, C, O, Ti, and Pb have been measured in the photon energy range k = 220–450 MeV using the tagged photon beam of the Bonn 500 MeV synchrotron. The hadron detector consists of a magnetic spectrometer and a large acceptance scintillation counter array. For Be, the single-arm energy distributions show clear structures from quasi-free pion production and quasi-deuteron photodisintegration. These structures disappear with increasing target size. The dependence of the differential cross section on the nuclear size S at Θ lab = 52° can be described by the power law d σ/ d Ω ∞ S α , where S is the number of protons or neutrons, respectively. The exponent is α π ≈ 0.6 for π − and π + and α p ≈ 1.15 for protons. Data for pn, pp, and pπ coincidences are presented. The results are compared to intranuclear cascade codes (PICA and PIKI) and to microscopic calculations.