Meson-baryon dynamics and the pp/a3dπ⁺ reaction: (I). Total and differential cross sections

We have obtained σ_tot and dσ/dΩ for π⁺d/a3pp using the most recent version of the Paris NN interaction. The model consists of the impulse approximation, p-wave pion and rho-meson rescattering following Δ₃₃ excitation, and s-wave rescattering constructed from the Koltun-Reitan lagrangian plus off-shell extrapolations. The rho mass distribution is described using the square of the Paris ƒ₋¹ helicity amplitude, and monopole form factors have been included in the internal πNN and πNΔ vertices. Recoil corrections to the impulse approximation are also considered and turn out to be important. Results are obtained with the Paris and Reid interactions as a function of the ρNΔ coupling constant, α_ρ = ƒ_ρ^∗/ƒ_ρ, and cutoffs Δ_π (varied between 1.7 and 2.0 and between 1.0 and 1.4 GeV respectively). Reasonable agreement with the experimental σ_tot can be obtained with either potential within the parameter ranges considered. Results for dσ/dΩ, parametrized in the form dσ/dΩ = (1/32π)(γ₀+γ₂ cos² θ+γ₄ cos⁴ θ+…), reveal that high partial waves (l_pp〉3) play a significant role, particularly in γ₄. This coefficient is particularly sensitive to α_ρ and may ultimately provide a constraint on that parameter.