Proton-Proton Triple Scattering at 1.9 GeV

We have measured the Wolfenstein triple-scattering parameters $R$, $D$, and $A^{\prime }$ at 1.9 GeV for $p-p$ scattering at 90° in the c.m. system. We find that $R=0.11\mathrm{}\pm 0.16$, $A^{\prime }=-0.54\mathrm{}\pm 0.16$, and $D=0.91\mathrm{}\pm 0.21$, where these parameters are defined in the c.m. system. The possibility of a vector character for the strong inter-actions is discussed. We conclude that neither a single vector-meson exchange nor a single pseudoscalar-meson exchange can account for the data. Spin effects are found to remain an important part of the nucleon-nucleon interaction at four-momentum transfer $-t=1.8\mathrm{}$ ${(\mathrm{G}\mathrm{e}\mathrm{V}/\mathit{c})}^2$.