Study of the reactionp↑p→pπ+n with polarized beam from 1.18 to 1.98 GeV/c

We present density-matrix elements and single-spin correlations for the reaction $p_{\uparrow }$p→p${\pi }^{+}$n at 1.18, 1.47, 1.71, and 1.98 GeV/c, using both longitudinal and transverse beam polarizations. For the $p_{\uparrow }$p→${\Delta }^{++}$n subprocess we find quite different energy dependence for the helicity-(1/2) and helicity-(3/2) ${\Delta }^{++}$-production asymmetries. The helicity-(1/2) asymmetry has $p_{\mathrm{lab}}$ dependence similar to the polarization in $p_{\uparrow }$p→${\pi }^{+}$d, while the helicity-(3/2) asymmetry changes sign between 1.18 and 1.47 GeV/c. By fitting the production angle dependence of the spin correlations, we obtain joint moments which are easily related to the partial-wave structure. We have carried out a partial-wave analysis with the moments data. We find that the production wave intensities are qualitatively consistent with the elastic phase-shift analyses, and the phases vary smoothly with $p_{\mathrm{lab}}$. From the absence of Breit-Wigner phase behavior, we conclude that the dinucleon resonances seen in the pp elastic waves are not true coupled-channel Briet-Wigner states in NN and NΔ.