Search for Three-Nucleon Force Effects in Analyzing Powers forp→dElastic Scattering

A series of measurements have been performed at KVI to obtain the vector analyzing power $A_y$ of the ${}^2\mathrm{H}(\overrightarrow{p},pd)$ reaction as a function of incident beam energy at energies of 120, 135, 150, and 170 MeV. For all these measurements, a range of ${\vartheta }_{\mathrm{c}.\mathrm{m}.\mathrm{}}$ from $30°$ to $170°$ has been covered. The purpose of these investigations is to observe possible spin-dependent effects beyond two-nucleon forces. When compared to the predictions of Faddeev calculations, based on two-nucleon forces only, significant deviations are observed at all energies and at center-of-mass angles between $70°$ and $130°$. The addition of present-day three-nucleon forces does not improve the description of the data, demonstrating the still insufficient understanding of the properties of three-nucleon systems.