Coulomb effects in nucleon-deuteron polarization-transfer coefficients

Coulomb effects in the neutron-deuteron and proton-deuteron polarization-transfer coefficients $K_y^{y'}$, $K_z^{x'}$, $K_y^{x'x'-y'y'}$ and $K_y^{z'z'}$ are studied at energies above the deuteron breakup threshold. Theoretical predictions for these observables are evaluated in the framework of the Kohn Variational Principle using correlated basis functions to expand the three-nucleon scattering wave function. The two-nucleon Argonne $v_{18}$ and the three-nucleon Urbana IX potentials are considered. In the proton-deuteron case, the Coulomb interaction between the two protons is included explicitly and the results are compared to the experimental data available at $E_{lab}=10,19,22.7$ MeV. In the neutron-deuteron case, a comparison to a recent measurement of $K_y^{y'}$ by Hempen {\sl et al.} at $E_{lab}=19$ MeV evidences a contribution of the calculated Coulomb effects opposite to those extracted from the experiment.