Energy dependence of the T(sup >) Gamow-Teller strength in p-shell nuclei observed in the (n,p) reaction

摘要

Cross sections have been measured for the transitions to the ground state of the residual nucleus using the (n,p) reaction on the targets(sup 6)Li, (sup 12)C, and (sup 13)C. A ''white'' continuum neutron source was utilized to measure cross sections for neutron energies from 60 to 260 MeV simultaneously. Charged particles were detected using a facility developed over the last few years which makes use of the five ''target'' wire chambers, four x and y multiwire drift chambers, a 5 kilo gauss magnetic field which deflects the charged particles out of the neutron beam, a wall of 15 CsI calorimeters, and a large-area plastic delta E detector. This arrangement allows four targets to be run simultaneously, and with magnet-on, scattering angles between 0 and 15 degrees can be measured concurrently as well. Angular distributions for the Gamow-Teller transitions are made and are extrapolated to q=0. At q=0 a simple expression relates the cross section to the volume integral for the effective nucleon-nucleon (N-N) interaction (J(sub (sigma)(tau))), the inverse (Beta)-decay matrix element and the distortion factor. For all transitions considered here B(sub GT) can be obtained from measured half-lifes and so the cross section measurements can be use to extract J(sub (sigma)(tau)) from 60 to 260 MeV. J(sub (sigma)(tau)) should be a smooth function of A. However, (p,n) experiments have been carried out, where cross sections were measured for the isobaric analog states of the transitions that are considered in this thesis, and the J(sub (sigma)(tau)) extracted were found to vary by as much as 40 percent for odd A nuclei as in the case of (sup 12)C(p,n) and (sup 13)C(p,n). This discrepancy will not be seen to exist in the (n,p) direction.