Spin observables for thepd↔π+treaction around theΔresonance

The proton analyzing power $A_{y0\mathrm{}}$ and the deuteron tensor analyzing power $T_{20}$ are evaluated for the $\mathrm{pd}\leftrightarrow {\pi }^{+}t$ process, in the energy region around and above the $\Delta$ resonance. These calculations extend a previous analysis of the excitation function and differential cross section, based on a model embodying one- and two-body $p$-wave absorption mechanisms and isobar excitation. The three-nucleon bound state and the $\mathrm{pd}$ scattering state are evaluated through Faddeev techniques for both the Bonn and Paris potentials. The spin variables exhibit a greater sensitivity to the number of included three-nucleon partial waves than the cross sections, while the role played by the initial- or final-state interactions appears to be small. The results for the tensor analyzing power at backward angles show a non-negligible dependence on the potentials employed, consistently with what has been previously found for the cross sections. The calculation of spin observables gives a clear indication that other reaction mechanisms (presumably $s$-wave two-body absorption) have to be included in the model, in order to reproduce the experimental data below the $\Delta$ resonance, in analogy with the simpler $\mathrm{pp}\leftrightarrow \pi d$ process.