Tensor polarisation of [formula omitted] in the [formula omitted] reaction at Ep = 41.3 MeV

Abstract

Angular correlation measurements have been made between the deuterons and the 12C g.s. product nuclei in the reaction 13 C( p,d) 12 C ∗(15.11 MeV, 1 +)(→ 120 C g.s. + γ) at deuteron scattering angles of 40°, 50°, 60°, and 75°, and a proton bombarding energy of 41.3 MeV. These measurements yield information concerning the k = 2 polarisation tensors ( t 2q) of the excited 12C nucleus produced in the direct (p, d) reaction. Cross-section angular distributions to the strongly excited g.s., 4.43, 12.71, 15.11 and 16.11 MeV states are also reported. Monte Carlo simulations of the laboratory distribution functions associated with the individual t kq were performed, incorporating the effects of finite geometry (beam spot and detector sizes), beam divergence, energy loss and multiple scattering of the 12C nuclei in the target. Finite range DWBA calculations were performed describing the polarisation tensors and cross sections, assuming a 1p neutron pickup. DWBA calculations for both conventional (elastic) and adiabatic d + 12C potentials were performed. Also, the effects of spin-orbit and the T r and T ℓ tensor potential were studied. The results confirmed that the “standard” DWBA formalism using an elastic d + 12C potential is inadequate for describing the recoil nucleus polarization. The use of adiabatic potentials, which arise from three-body effects, produced an improvement in the description of the extracted data. The DWBA calculations showed only a modest sensitivity to inclusion of spin-orbit and the T r or T ℓ tensor terms in the deuteron optical potential.