J. Shaw

The 13C(γ,π−)13N reaction at Eγ≈ 184 MeV (Tπ ≈ 41 MeV)

Abstract Differential cross sections for the 13 C( γ , π − ) 13 N reaction at E γ ≈ 184 MeV ( T π ≈ 41 MeV) were measured with the Saskatoon tagged-photon facility and two range-telescope detectors. Data were obtained at pion angles of 45°, 60°, 80° and 100°, with emphasis on the forward angles, where the cross section shows a strong rise. The present data, together with existing ones at larger angles, are compared to several theoretical calculations.

Distribution of spin-isospin strengths in 12B and 13B

Abstract The differential cross sections of the reactions 12,13 C( γ , π + ) 12,13 B were measured using tagged photons at the mean energy E γ = 191 MeV at five angles 35° ⩽ θ π ⩽ 145° corresponding to the momentum transfer to the nucleus 0.5 ⩽ q ⩽ 1.5 fm −1 . The major transition strengths leading to various excited states in 12,13 B, in both cases, are concentrated within a resonance centered at about 7 MeV excitation energy in 12,13 B (about 22 MeV in 12,13 C) with a full width at half maximum (FWHM) of about 12 MeV, reminiscent of the well-known electric-dipole gian resonances. The two reactions are compared in the context of the weak-coupling model.

Positive photopion production from 12,13C using tagged photons

Abstract Angular distributions of positive pions to residual states in 12 B and 13 B at excitation energies up to 20 MeV were measured using tagged photon facility at SAL. Strong spin-isospin flip ( Δ S=1, Δ T=1) states are clearly observed in the excitation spectra of both 12 B and 13 B. Present data were found to be in good agreement with existing data. J.C. Kim and H.T. Chung gratefully acknowledges the support of SNU Daewoo Research Fund. K. Shoda and H. Tsubota want to thank the Monbusho International Scientific Research Program No. 63044011 for supporting this work.

The 14N(γ, π+)14Cg.s. reaction through the delta resonance region

Abstract The pion angular distribution for 14 N( γ , π + ) 14 C g.s. has been measured at a photon energy of 400 MeV. The energy dependence of the cross section through the delta region, and the apparent strength of the resonance contribution, as determined by the present measurement together with earlier lower energy measurements, cannot be accounted for by any current theory. Calculations which use the delta-hole model in the resonance channel overestimate the present results by a factor of over two.