Excitation of spin-isospin giant resonance states in 12c(gamma,pi+)12b using tagged photons

The angular distribution of positive pions from the reaction, 12C(gamma,pi+)12B* were measured at five angles (theta= 35°, 55°, 90°, 125°, 145°) using the tagged photons in the range 176 < Egamma < 182 MeV. The pi+ spectra were measured with a system of DeltaE-E plastic scintillator telescopes. The separation of pi+ from other particles was achieved by measuring the DeltaE vs. E scatter plot and also by observing the delayed decay muons from the stopped pi+ in the E-detector

Spin-isospin excitation in 12C(γ, π+)12B∗ using tagged photons

The energy spectra of positive pions from the reaction 12C(γ, π+)12B∗ were measured at five angles, using quasi-monochromatic, tagged photons in the energy range from 176 to 182 MeV. Strong transitions to the isovector nuclear states in 12B at 0–1, 4.5, and 7.5 MeV were observed. The differential cross sections to these states have been obtained for the momentum transfers 0.5 < q < 1.2 fm−1. DWIA calculations have been carried out in momentum space for each observed state or group of states. Comparisons are made between the present data, previous data from bremsstrahlung experiments, and various DWIA calculations

Spin-isospin excitation in 12C(γ, π+)12B∗ using tagged photons

The energy spectra of positive pions from the reaction 12C(γ, π+)12B∗ were measured at five angles, using quasi-monochromatic, tagged photons in the energy range from 176 to 182 MeV. Strong transitions to the isovector nuclear states in 12B at 0–1, 4.5, and 7.5 MeV were observed. The differential cross sections to these states have been obtained for the momentum transfers 0.5 < q < 1.2 fm−1. DWIA calculations have been carried out in momentum space for each observed state or group of states. Comparisons are made between the present data, previous data from bremsstrahlung experiments, and various DWIA calculations

Detection of low energy pions at a tagged photon beam

In order to measure pions in the range 10–30 MeV from the reaction 12C(γ, π+)12B∗ using monochromatic photons, for a study of excited collective spin-isospin analog states [1], a detection system for positive pions, which reduces the backgrounds from electrons and protons by very large factors, was developed. The techniques and detectors used, namely a ΔE - E plastic scintillation telescope with separate photomultipliers and a glued triple sandwich of CaF2-plastic-CaF2 scintillators, are described here