Polarization and Angular Distribution of the Neutrons fromC14(p,n)Reaction and the Tensor Force

The polarization of the neutrons from the ${}_{}{}^{14}{}_{}{}^{}\mathrm{C}\mathrm{}(p,n)\mathrm{}$ reaction leading to the first three levels of ${}_{}{}^{14}{}_{}{}^{}\mathrm{N}$ has been measured at six bombarding energies between 7.2 and 13.3 MeV. The polarization and angular distribution of the neutrons leading to the two $1^{+}$ states have been analyzed with a microscopic distorted-wave Born-approximation formalism that has been extended to include spin-orbin optical distortions and a tensor component in the effective two-body force; the analog-state transition has been analyzed with the Lane model. The angular distribution and polarization shapes for the analog transition are not well reproduced by the Lane model, primarily because of lack of precise optical parameters as a function of bombarding energy. However, the integrated cross sections between 8.8 and 18.3 MeV are reasonably well accounted for with a constant real and imaginary isospin strength of 88 and 40 MeV, respectively. The corresponding real microscopic charge-exchange strength is $V_{\tau }=9\mathrm{}$ MeV for a Yukawa form factor of range 1.4 fm. The calculated $1^{+}$ angular-distribution shapes are in fair agreement with measurements and are consistent with a constant central spin-spin and tensor strength between 10.4- and 18.3-MeV bombarding energy: $V_{\sigma \tau }=7\mathrm{}\pm 1$ MeV and $V_T=4.7\mathrm{}\pm 0.7$ MeV, although there is some indication that the tensor strength is decreasing with increasing energy. Contrary to the angular-distribution measurements, the $1^{+}$ polarization measurements do not clearly favor a tensor component in the effective two-body force; neither the pure central nor the central-plus-tensor polarization calculation fits the data particularly well. This disagreement is probably due to optical-parameter uncertainities and contributions from second-order processes, and possibly to the neglect of tensor exchange and small admixtures of intermediate-structure resonance processes.